mirror of
https://github.com/pevans/erc-c.git
synced 2024-11-27 20:51:17 +00:00
139 lines
4.9 KiB
Markdown
139 lines
4.9 KiB
Markdown
# erc
|
|
### (Emulator of old, Retro Computers)
|
|
|
|
---
|
|
|
|
Erc is software that allows you to emulate computers from the days of
|
|
yore. (The "days of yore" may be defined as the 1980s.) You may find it
|
|
interesting if you feel nostalgia for those old machines, or if you want
|
|
to see how those computers worked.
|
|
|
|
Erc is also a sound you might make when feeling slightly frustrated, or
|
|
if you were a small cat that happens to make funny sounds that aren't
|
|
quite meows.
|
|
|
|
## Goals
|
|
|
|
I've long had an interest in retro computing, collecting books on the
|
|
6502 processor in particular, and this program has been written and
|
|
rewritten in fits and starts over several years (and in several
|
|
languages!). Being able to emulate the Apple II, which was my childhood
|
|
computer, has been a dream of mine for some time!
|
|
|
|
Erc is written in C, largely because I have long loved that language,
|
|
though I have not had much need to use it in my professional career. C
|
|
is a somewhat cranky language, and not one that lends itself to modern
|
|
engineering practices, so erc was partly written as a challenge to
|
|
myself to try and elevate the language.
|
|
|
|
In particular, it's a goal of mine to ensure that erc:
|
|
|
|
* is written for other developers to read, especially as a reference for
|
|
those who are interested in emulation in general and the platforms
|
|
emulated here in particular;
|
|
* is modular, allowing as much code reuse within the application as is
|
|
practical;
|
|
* is unit-testable, to the extent that C allows, and maintains a high
|
|
level of code coverage.
|
|
|
|
## Updates (Jan 18, 2018)
|
|
|
|
I thought I'd write something on the state of the emulator. Here's
|
|
what's done so far:
|
|
|
|
* We have fully implemented the MOS 6502 processor support for the Apple
|
|
II, and we have much of the infrastructure to emulate an Apple II
|
|
machine in place now.
|
|
* Memory organization is principally complete. There's a lot of memory
|
|
in the Apple II! You have main memory, auxiliary memory,
|
|
bank-switchable memory, read-only memory. Early on, we implemented
|
|
memory map support for vm_segments, which is something that has
|
|
been flexible enough to support all of the types of soft-switches
|
|
that the Apple II has to control access to said memory (as well as
|
|
for many other functions).
|
|
* There's a basic disassembler in place for the 6502 support, which has
|
|
been incredibly helpful in identifying where we have had functional
|
|
breakdowns in terms of proper execution and bootstrapping of the
|
|
"machine".
|
|
* We're up to 169 tests as of the time of this writing, which is
|
|
awesome!
|
|
|
|
We do have a lot of stuff done for the graphics system, but there's a
|
|
lot more to go; getting graphics and text working as intended is my next
|
|
goal. I'm hopeful this will lead us to a point where erc is usable with
|
|
general disk images of software.
|
|
|
|
Some ideas for the future:
|
|
|
|
* An assembler that could splice a program into multiple disk images
|
|
* Commadore 64 support (which will be difficult, as I've used a
|
|
Commadore maybe...one time? Two times?)
|
|
|
|
## Running
|
|
|
|
Running erc right now is a bit hazardous; not in the sense that it will
|
|
break anything, but more in the sense that you may not know what you
|
|
should be doing. Since it is still somewhat in flux, I won't go into too
|
|
much detail on how you can run it; I will point you to the help
|
|
printout, which you can see by doing this:
|
|
|
|
```
|
|
./erc --help
|
|
```
|
|
|
|
(The above assumes you have built the software in the `build` subdir,
|
|
and are actually in that subdir.) Generally speaking, you can indicate
|
|
what you have in one of two "disk drives", given a valid disk image for
|
|
an Apple II (e.g. something ending in .dsk, .do, etc., and having the
|
|
proper length for said image).
|
|
|
|
## Compiling and installing
|
|
|
|
This software uses CMake to build its makefiles, so if you're familiar
|
|
with that, you should feel somewhat at home.
|
|
|
|
If you've never compiled any C code before, you will need to install a
|
|
few things first. If you have not done so, you should install the
|
|
excellent [Homebrew](https://brew.sh/) if using a Mac. If you are using
|
|
Linux, you are probably already acquainted with your local package
|
|
manager. You will also need to have XCode installed in a Mac
|
|
environment. You can do so through the App Store.
|
|
|
|
The following other things you must install are given as Homebrew
|
|
commands. If you are using Linux, I will leave the appropriate commands
|
|
you must run as an exercise for the reader.
|
|
|
|
```
|
|
brew install cmake
|
|
brew install snaipe/soft/criterion
|
|
```
|
|
|
|
Once all that is accomplished, you can do this:
|
|
|
|
```
|
|
cd build
|
|
cmake ..
|
|
make
|
|
```
|
|
|
|
This should produce an executable of the emulator, which you can install
|
|
wherever you wish.
|
|
|
|
## Testing
|
|
|
|
If you're feeling a bit nosy, you can run unit tests by doing the following:
|
|
|
|
```
|
|
cd tests/build
|
|
cmake ..
|
|
make; ./erc-test
|
|
```
|
|
|
|
This will execute the testing build of the software, which is handled
|
|
through [Criterion](https://github.com/Snaipe/Criterion).
|
|
|
|
## Contributing
|
|
|
|
Right now, I am not accepting pull requests as so much of the design of
|
|
erc is in flux. I am happy to receive any issues you may file.
|