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Minimises video flushing, moves it to the proper time.

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This commit is contained in:
Thomas Harte 2021-03-22 09:02:49 -04:00
parent 7965772745
commit 42a9dc7c2b
1 changed files with 53 additions and 38 deletions
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91
Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp
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@ -152,15 +152,13 @@ template<Model model> class ConcreteMachine:
case PartialMachineCycle::ReadStart:
case PartialMachineCycle::WriteStart:
// Apply contention if necessary.
// For now this causes a video sync up every time any contended area is written to.
// TODO: flush only upon a video-area write.
//
// Assumption here: the trigger for the ULA inserting a delay is the falling edge
// of MREQ, which is always half a cycle into a read or write.
//
// TODO: somehow provide that information in the PartialMachineCycle?
if(is_contended_[address >> 14]) {
delay = video_->access_delay(HalfCycles(1));
delay = video_.last_valid()->access_delay(video_.time_since_flush() + HalfCycles(1));
}
break;
@ -170,6 +168,10 @@ template<Model model> class ConcreteMachine:
break;
case PartialMachineCycle::Write:
// Flush video if this access modifies screen contents.
if(address >= video_base_ && address < video_base_ + 6912) {
video_.flush();
}
write_pointers_[address >> 14][address] = *cycle.value;
break;
@ -188,12 +190,12 @@ template<Model model> class ConcreteMachine:
// Test for classic 128kb paging register.
if((address & 0xc002) == 0x4000) {
// Set the proper video base pointer.
set_video_address();
port7ffd_ = *cycle.value;
update_memory_map();
// Set the proper video base pointer.
set_video_address();
// Potentially lock paging, _after_ the current
// port values have taken effect.
disable_paging_ |= *cycle.value & 0x20;
@ -203,6 +205,7 @@ template<Model model> class ConcreteMachine:
if((address & 0xf002) == 0x1000) {
port1ffd_ = *cycle.value;
update_memory_map();
update_video_base();
}
if((address & 0xc002) == 0xc000) {
@ -369,7 +372,9 @@ template<Model model> class ConcreteMachine:
std::array<uint8_t, 16*1024> scratch_;
const uint8_t *read_pointers_[4];
uint8_t *write_pointers_[4];
uint8_t pages_[4];
bool is_contended_[4];
int video_base_ = 0x4000;
uint8_t port1ffd_ = 0;
uint8_t port7ffd_ = 0;
@ -388,56 +393,66 @@ template<Model model> class ConcreteMachine:
switch(port1ffd_ & 0x06) {
default:
case 0x00:
set_memory(0, &ram_[0 * 16384], &ram_[0 * 16384], false);
set_memory(1, &ram_[1 * 16384], &ram_[1 * 16384], false);
set_memory(2, &ram_[2 * 16384], &ram_[2 * 16384], false);
set_memory(3, &ram_[3 * 16384], &ram_[3 * 16384], false);
set_memory(0, 0);
set_memory(1, 1);
set_memory(2, 2);
set_memory(3, 3);
break;
case 0x02:
set_memory(0, &ram_[4 * 16384], &ram_[4 * 16384], true);
set_memory(1, &ram_[5 * 16384], &ram_[5 * 16384], true);
set_memory(2, &ram_[6 * 16384], &ram_[6 * 16384], true);
set_memory(3, &ram_[7 * 16384], &ram_[7 * 16384], true);
set_memory(0, 4);
set_memory(1, 5);
set_memory(2, 6);
set_memory(3, 7);
break;
case 0x04:
set_memory(0, &ram_[4 * 16384], &ram_[4 * 16384], true);
set_memory(1, &ram_[5 * 16384], &ram_[5 * 16384], true);
set_memory(2, &ram_[6 * 16384], &ram_[6 * 16384], true);
set_memory(3, &ram_[3 * 16384], &ram_[3 * 16384], false);
set_memory(0, 4);
set_memory(1, 5);
set_memory(2, 6);
set_memory(3, 3);
break;
case 0x06:
set_memory(0, &ram_[4 * 16384], &ram_[4 * 16384], true);
set_memory(1, &ram_[7 * 16384], &ram_[7 * 16384], true);
set_memory(2, &ram_[6 * 16384], &ram_[6 * 16384], true);
set_memory(3, &ram_[3 * 16384], &ram_[3 * 16384], false);
set_memory(0, 4);
set_memory(1, 7);
set_memory(2, 6);
set_memory(3, 3);
break;
}
return;
} else {
// Apply standard 128kb-esque mapping (albeit with extra ROM to pick from).
set_memory(0, 0x80 | ((port1ffd_ >> 1) & 2) | ((port7ffd_ >> 4) & 1));
set_memory(1, 5);
set_memory(2, 2);
set_memory(3, port7ffd_ & 7);
}
// Apply standard 128kb-esque mapping (albeit with extra ROM to pick from).
const auto rom = &rom_[ (((port1ffd_ >> 1) & 2) | ((port7ffd_ >> 4) & 1)) * 16384];
set_memory(0, rom, nullptr, false);
set_memory(1, &ram_[5 * 16384], &ram_[5 * 16384], true);
set_memory(2, &ram_[2 * 16384], &ram_[2 * 16384], false);
const auto high_ram = &ram_[(port7ffd_ & 7) * 16384];
set_memory(3, high_ram, high_ram, (port7ffd_ & 7) >= 4);
}
void set_memory(int bank, const uint8_t *read, uint8_t *write, bool is_contended) {
is_contended_[bank] = is_contended;
read_pointers_[bank] = read - bank*16384;
write_pointers_[bank] = (write ? write : scratch_.data()) - bank*16384;
void set_memory(int bank, uint8_t source) {
is_contended_[bank] = (source >= 4 && source < 8);
pages_[bank] = source;
uint8_t *read = (source < 0x80) ? &ram_[source * 16384] : &rom_[(source & 0x7f) * 16384];
const auto offset = bank*16384;
read_pointers_[bank] = read - offset;
write_pointers_[bank] = ((source < 0x80) ? read : scratch_.data()) - offset;
}
void set_video_address() {
video_->set_video_source(&ram_[((port7ffd_ & 0x08) ? 7 : 5) * 16384]);
update_video_base();
}
void update_video_base() {
const uint8_t video_page = (port7ffd_ & 0x08) ? 7 : 5;
video_base_ = 0x1'0000; // i.e. not in memory.
if(pages_[0] == video_page) video_base_ = 0x0000;
else if(pages_[1] == video_page) video_base_ = 0x4000;
else if(pages_[2] == video_page) video_base_ = 0x8000;
else if(pages_[3] == video_page) video_base_ = 0xc000;
}
// MARK: - Audio.