mirror of
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Reworking the memory manager API, started coding.
This commit is contained in:
Martin Haye
parent
69116f7bad
commit
7bc7c94f8b
@ -1,155 +1,299 @@
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;Memory manager
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;------------------
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;Memory is managed in 512-byte blocks (to correspond with Prodos block sizes)
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;In every 64kb memory bank, a lookup table lives at $800-$8FF and identifies
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;what blocks, if any, are used there as well as usage flags to mark free,
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;used, or reserved memory.
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; Memory manager
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; ------------------
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;
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;Memory is marked as used as it is loaded by the loader, but the caller program
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;should mark memory as free as soon as the memory is no longer in use. It is
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;very possible that the memory will not be reclaimed right away and could be
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;reinstated as in-use without a loading penalty.
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; Memory is managed in 256-byte pages (to correspond with Prodos block sizes)
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; In each 48kb memory bank (main and aux), a lookup table identifies what pages,
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; if any, are used there as well as usage flags to mark free, used, or reserved memory.
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;
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;Another scenario is that free memory will be relocated to auxiliary banks
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;and potentially later restored to active memory at a later time. Depending on the
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;driver, this might be handled in different ways. Aux memory should be kept open
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;such that memory can still be reclaimed. Extended memory (e.g. RamWorks and slinky
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;ram expansions) can adopt a more linear and predictable model if they are large enough.
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; Memory is marked as used as it is loaded by the loader, but the caller program
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; should mark memory as free as soon as the memory is no longer in use. It is
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; very possible that the memory will not be reclaimed right away and could be
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; reinstated as in-use without a loading penalty.
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;
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;The goal of using extended ram is to prevent future disk access as much as possible,
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;because even an inefficient o(N) memory search is going to be faster than spinning up
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;a disk.
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;-----------------
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;Page table format:
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;FFFFFppp nnnnnnnn
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;F = Flags
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; 7 - Active/Inactive
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; Another scenario is that free memory will be relocated to auxiliary banks
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; and potentially later restored to active memory at a later time. Depending on the
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; loader, this might be handled in different ways. Aux memory should be kept open
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; such that memory can still be reclaimed. Extended memory (e.g. RamWorks and slinky
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; ram expansions) can adopt a more linear and predictable model if they are large enough.
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;
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; Memory operations are performed in sets. A set is begun with the START_LOAD call, and
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; subsequent QUEUE_LOAD requests are queued up. The set is then executed with
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; FINISH_LOAD. The purpose of queuing the requests is to allow the disk driver to
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; sort the requests in storage order and thus optimize loading speed. During the period
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; between START_LOAD and FINISH_LOAD, the area in main memory from $4000 to 5FFF is
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; reserved for memory manager operations. Therefore, if hi-res graphics are showing it
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; is important to copy them to page 1 ($2000.3FFF) and switch to that display before
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; queueing loads.
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;
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; The goal of using extended ram is to prevent future disk access as much as possible,
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; because even an inefficient o(N) memory search is going to be faster than spinning up
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; a disk.
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;
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; ----------------------------
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; Page table format in memory:
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; FFFFtttt nnnnnnnn
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; F = Flags
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; 7 - Active/Inactive
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; 6 - Locked (Cannot reclaim for any reason)
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; 5 - Code (1) or Data (0)
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; 4 - Primary (1) or Secondary (0)
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; Memory blocks are allocated in chunks, the first block is always primary
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; So detecting primary blocks means we can clear more than one block at a time
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; 3 - Reserved
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;p = Data partition (0-7)
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;n = Block number (0-256)
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; 5 - Primary (1) or Secondary (0)
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; Memory pages are allocated in chunks, the first page is always primary
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; So detecting primary pages means we can clear more than one page at a time
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; 4 - Loaded (Memory contains copy of disk-based resource identified below)
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; t = Type of resource (1-15, 0 is invalid)
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; n = Resource number (1-255, 0 is invalid)
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;
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*=$900
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PAGE_TABLE = $800
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READ equ $CA
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READ_BLOCK equ $80
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ERROR_IO equ $27
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NOT_CONNECTED equ $28
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; -------------------------
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; Page file format on disk:
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; File must be named: DISK.PART.nnn where nnn is the partition number (0-15)
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; File Header:
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; byte 0: Total # of pages in header
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; byte 1-n: Table of repeated resource entries
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; Resource entry:
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; byte 0: resource type (1-15), 0 for end of table
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; byte 1: resource number (1-255)
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; byte 2: number of pages
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; The remainder of the file is the page data for the resources, in order of
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; their table appearance.
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;
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mainLoader = $800
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auxLoader = $803
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INIT_BLOCK_TABLE
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; Set up block table, marking ZP, Stack, $800-$9FF, Hires, and Prodos system areas as locked.
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; Large memory drivers should keep blocks in their canonical order if they have
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; enough space (>= 800kb). Since it is only needed to reserve memory in AUX and Main memory,
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; other drivers can omit block tables if they have sufficient memory. In these
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; situations it might work best if large memory drivers use an alternate
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; approach to a block table as it makes sense to do so.
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; Monitor routines
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setNorm = $FE84
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monInit = $FB2F
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setVid = $FE93
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setKbd = $FE89
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REQUEST_MEMORY
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; Free memory, relocating anything in the way to auxiliary ram if possible
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; The end result is that the caller gets a target area of ram to use that is supposedly
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; not in use by anything else (provided it plays nicely with others...)
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; If we have to satisfy the target block location (A > 0) then active flags are
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; ignored right away. It is necessary for transition code to always make sure
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; that non-relocatable code segments are loaded in their required places before
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; JMPing to them.
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;
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; A = requested target block location, 0 = don't care
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; 0 is used because we will never want to load into the stack or into zero page on purpose
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; Some loaders in the chain will let us use block 0, but that's only for AUX banks
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; Y = number of blocks to reserve
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; Returns: A = target location
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; If carry set, allocation failed!
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;------------------------------------------------------------------------------
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; Command codes
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LOCK_MEMORY
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; Set memory as locked so that it cannot be reclaimed for any reason.
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; A = starting block number
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; Y = number of blocks to lock (0 or 1 both mean one block)
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;------------------------------------------------------------------------------
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RESET_MEMORY = $10
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; Input: None
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;
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; Output: None
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;
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; Mark all memory as inactive, except the following areas in main memory
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; which are always locked:
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;
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; 0000.01FF: Zero page and stack
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; 0200.02FF: Input buffer and/or scratch space
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; 0300.03FF: System vectors, scratch space
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; 0400.07FF: Text display
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; 0800.xxxx: The memory manager and its page table
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; BF00.BFFF: ProDOS system page
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;
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; Note that this does *not* destroy the contents of memory, so for instance
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; future RECALL_MEMORY commands may be able to re-use the existing contents
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; of memory if they haven't been reallocated to something else.
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;
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; This command is acted upon and then passed on to chained loaders.
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RELOCATE_MEMORY
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; Move blocks down the loader chain to whoever can hold them
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; The goal is to relocate blocks and avoid going back to disk if possible
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; If this goal cannot be met, then cest la vie! :-)
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; A reallocation request is reviewed block by block. A loader can ignore
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; relocation requests for blocks they still have in memory, even if inactive
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; A = starting block to relocate
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; Y = number of blocks to relocate
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; Returns: Nothing
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DEACTIVATE_MEMORY
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; Mark a block in memory as free, or rather inactive, so that it can be reused
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; This also clears the lock bit! Subsequent blocks are also freed if their
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; primary bit is not set. Callers shouldn't use this directly, you
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; should use REQUEST_MEMORY!
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; A = block number
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; Return: nothing
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FIND_BLOCK
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; Check to see if block is in memory
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; A = partition number (0-7)
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; Y = block number
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; Returns:
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; Carry clear if block found
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; A = block number in memory (LSB)
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; Y = block number in memory (MSB)
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; Carry set if block not found
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; See load block for failure status codes
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;------------------------------------------------------------------------------
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LOCK_MEMORY = $11
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; Input: X-reg - page address for start of reservation
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; Y-reg - number of pages to reserve
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;
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; Output: None
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;
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; Reserve a specific area of memory. If it cannot be reserved for any reason,
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; a FATAL_ERROR is triggered.
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;
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; This command is acted upon immediately and chained loaders are not called.
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RECALL_BLOCKS
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; This is the main loader stub, used to transfer a set of blocks from the most accessible
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; location to main memory. For main memory, this is a stub to move memory if possible
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; or just delegate the work of loading down the chain to the next available device
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; in the loader chain.
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; If the block is not found and there are no more loaders in the chain,
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; then an error code is returned.
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; When blocks are loaded, only the first block is marked primary, others are marked
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; as secondary.
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; A = Requested target block location in memory
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; X = NNNNNPPP;
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NNNNN = number of blocks to load (+1 added to value, so 11111 will load 32 blocks)
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PPP = Partition number (0-7)
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; Y = Starting block number (0-256)
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; Returns: Carry clear if successful
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; If carry is set, check A for failure status:
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; 255 = I/O error
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; 0 = partition not found (disk switch required)
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; 1 = block not found (partition size is too small, probably needs boot disk)
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JSR MLI
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db READ_BLOCK
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db 3 ; param count
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db 1 ; unit num (Bit 7 = drive, Bits 6-4 = slot)
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dw 00 ; buffer location (little endian)
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dw 00 ; block # (little endian)
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;------------------------------------------------------------------------------
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REQUEST_MEMORY = $12
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; Input: X-reg - number of pages to allocate
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;
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; Output: X-reg - starting memory page that was allocated
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;
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; Allocate a number of blocks in the memory space of this loader. If there
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; isn't a large enough continguous memory segment available, the system
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; will be halted immediately with HALT_MEMORY.
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;
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; To allocate main memory, call the main memory loader. To allocate aux
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; mem, call that loader instead.
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;
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; This command is acted upon immediately and chained loaders are not called.
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REGISTER_LOADER
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; Register loader to the end to the loader chain.
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; So if this has a chain loader registered already, perform a JMP to that loader
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; Priority is lowest-to-highest order so things should be in this order:
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; 00: Main memory
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; 10: Slinky ram (>= 1mb -- can hold full game)
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; 20: RamWorks (>= 1mb -- can hold full game)
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; 30: Slinky ram (< 800kb -- unable to hold full game)
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; 40: RamWorks (< 800kb -- unable to hold full game)
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; 50: Aux memory
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; 60: Hard drive/800kb -- Holds full game but slow
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; 70: Disk II -- Unable to hold full game and also very slow
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; 80: Serial -- Able to hold full game but really slow and requires extra checks
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;
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; Inputs:
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; A = Priority
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; Y = MSB loader address
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; X = LSB loader address
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;------------------------------------------------------------------------------
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START_LOAD = $13
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; Input: X-reg - disk partition number (0 for boot disk, 1-15 for others)
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;
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; Output: None
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;
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; Marks the start of a set of QUEUE_LOAD operations, that will be
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; acted upon when FINISH_LOAD is finally called.
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;
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; The partition is recorded and passed on to chained loaders.
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;------------------------------------------------------------------------------
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QUEUE_LOAD = $14
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; Input: X-reg - resource type
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; Y-reg - resource number
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;
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; Output: X-reg - memory page the load will occur at
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;
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; This is the main entry for loading resources from disk. It queues a load
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; request, allocating main memory to hold the entire resource. Note that
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; the load is only queued; it will be completed by FINISH_LOAD.
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;
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; Note that if the data is already in memory, its former location will
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; be returned and no disk access will be queued.
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;
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; The request is either acted upon by this loader, or passed onto the
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; next chained loader. If there is no next loader, a FATAL_ERROR is
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; triggered.
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;------------------------------------------------------------------------------
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FINISH_LOAD = $15
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; Input: None
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;
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; Output: None
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;
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; Completes all prior QUEUE_LOAD requests, clearing the queue. It's the
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; last part of a START_LOAD / QUEUE_LOAD / FINISH_LOAD sequence.
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;
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; This command is acted upon by this loader and passed to chained loaders.
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;------------------------------------------------------------------------------
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FREE_MEMORY = $16
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; Input: X-reg - starting page number to mark free (must be start of a
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; memory area that was requested, locked, or loaded)
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;
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; Output: None
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;
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; Mark a block of memory as free, or rather inactive, so that it can be
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; reused. This also clears the lock bit!
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;------------------------------------------------------------------------------
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FATAL_ERROR = $17
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; Input: X-reg / Y-reg: message number or pointer (see below)
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;
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; Output: Never returns
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;
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; Switches to text mode, prints out a predefined or custom error message,
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; plus the call stack, and then halts the system (i.e. it waits forever,
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; user has to press Reset).
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;
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; If Y-reg is zero, this prints one of these predefined messages based on
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; X-reg:
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LOAD_ERR_INVALID_COMMAND = $01
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LOAD_ERR_BAD_PARAM = $02
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LOAD_ERR_OUT_OF_MEMORY = $03
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LOAD_ERR_RESERVED_MEM = $04
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LOAD_ERR_UNKNOWN = $05
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;
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; If Y-reg is non-zero, it's taken as the high byte of a pointer to
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; a zero-terminated, ASCII message to print. X-reg is the low byte of the
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; message pointer.
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;
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; This command halts and thus never returns.
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;------------------------------------------------------------------------------
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; code begins here
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* = $800
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jmp mainLoader
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jmp auxLoader
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nextLoaderVec: jmp diskLoader
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mainLoader:
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lda #0 ; incremented after init
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bne :+
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jmp init
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: cmp #RESET_MEMORY
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bne :+
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jmp main_reset
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: cmp #LOCK_MEMORY
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bne :+
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jmp main_lock
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: cmp #REQUEST_MEMORY
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bne :+
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jmp main_req
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: cmp #FATAL_ERROR
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bne :+
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jmp fatalError
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: cmp #START_LOAD
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bcc cmdError
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cmp #FINISH_LOAD+1
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bcs cmdError
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; Found a command that needs to be chained to next loader
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jmp nextLoaderVec
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cmdError:
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ldx #LOAD_ERR_INVALID_COMMAND
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ldy #0
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fatalError:
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tya
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bne customErr
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predefErr:
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dex
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beq foundErrMsg
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: iny
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lda errorText,y
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bne :-
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beq predefErr
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foundErrMsg:
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tya
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clc
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adc #<errorText
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tax
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ldy #>errorText
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bcc customErr
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iny
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customErr:
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sty pTmp+1
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stx pTmp
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; Set up text mode, print message
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printErr:
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jsr setNorm
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jsr monInit
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jsr setVid
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jsr setKbd
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jsr crout
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jsr crout
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ldy #0
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: lda (pTmp),y
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beq :+
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jsr cout
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iny
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bne :-
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; Print call stack
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jsr crout
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tsx
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: cpx #$FF
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beq :+
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inx
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lda 100,x
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sec
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sbc #2
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sta pTmp
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lda 101,x
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sbc #0
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sta pTmp+1
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and #$C0
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cmp #$C0
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beq :-
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ldy #0
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lda (pTmp),y
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cmp #$20
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bne :-
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lda pTmp+1
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jsr prByte
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lda pTmp
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jsr prByte
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lda #$A0
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jsr cout
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jmp :-
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; Beep, and loop forever
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: jsr bell
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loopForever: jmp loopForever
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errorText:
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.byte "Invalid command", 0
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.byte "Bad parameter", 0
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.byte "Reserved memory", 0
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.byte "Unknown error", 0
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.byte 0
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