byuu says:
Changelog:
- SMS: extended bus mapping of in/out ports: now decoding them fully
inside ms/bus
- SMS: moved Z80 disassembly code from processor/z80 to ms/cpu
(cosmetic)
- SMS: hooked up non-functional silent PSG sample generation, so I can
cap the framerate at 60fps
- SMS: hooked up the VDP main loop: 684 clocks/scanline, 262
scanlines/frame (no PAL support yet)
- SMS: emulated the VDP Vcounter and Hcounter polling ... hopefully
it's right, as it's very bizarre
- SMS: emulated VDP in/out ports (data read, data write, status read,
control write, register write)
- SMS: decoding and caching all VDP register flags (variable names
will probably change)
- nall: \#undef IN on Windows port (prevent compilation warning on
processor/z80)
Watching Sonic the Hedgehog, I can definitely see some VDP register
writes going through, which is a good sign.
Probably the big thing that's needed before I can get enough into the
VDP to start showing graphics is interrupt support. And interrupts are
never fun to figure out :/
What really sucks on this front is I'm flying blind on the Z80 CPU core.
Without a working VDP, I can't run any Z80 test ROMs to look for CPU
bugs. And the CPU is certainly too buggy still to run said test ROM
anyway. I can't find any SMS emulators with trace logging from reset.
Such logs vastly accelerate tracking down CPU logic bugs, so without
them, it's going to take a lot longer.
byuu says:
Changelog:
- Z80: added most opcodes between 0x00 and 0x3f (two or three hard
ones missing still)
- Z80: redid register declaration *again* to handle AF', BC', DE',
HL' (ugggggh, the fuck? Alternate registers??)
- basically, using `#define <register name>` values to get around
horrendously awful naming syntax
- Z80: improved handling of displace() so that it won't ever trigger
on (BC) or (DE)
byuu says:
Changelog:
- Z80: implemented 113 new instructions (all the easy
LD/ADC/ADD/AND/OR/SBC/SUB/XOR ones)
- Z80: used alternative to castable<To, With> type (manual cast inside
instruction() register macros)
- Z80: debugger: used register macros to reduce typing and increase
readability
- Z80: debugger: smarter way of handling multiple DD/FD prefixes
(using gotos, yay!)
- ruby: fixed crash with Windows input driver on exit (from SuperMikeMan)
I have no idea how the P/V flag is supposed to work on AND/OR/XOR, so
that's probably wrong for now. HALT is also mostly a dummy function for
now. But I typically implement those inside instruction(), so it
probably won't need to be changed? We'll see.
byuu says:
Changelog:
- added (poorly-named) castable<To, With> template
- Z80 debugger rewritten to make declaring instructions much simpler
- Z80 has more instructions implemented; supports displacement on
(IX), (IY) now
- added `Processor::M68K::Bus` to mirror `Processor::Z80::Bus`
- it does add a pointer indirection; so I'm not sure if I want to
do this for all of my emulator cores ...
byuu says:
Changelog:
- rewrote the Z80 core to properly handle 0xDD (IX0 and 0xFD (IY)
prefixes
- added Processor::Z80::Bus as a new type of abstraction
- all of the instructions implemented have their proper T-cycle counts
now
- added nall/certificates for my public keys
The goal of `Processor::Z80::Bus` is to simulate the opcode fetches being
2-read + 2-wait states; operand+regular reads/writes being 3-read. For
now, this puts the cycle counts inside the CPU core. At the moment, I
can't think of any CPU core where this wouldn't be appropriate. But it's
certainly possible that such a case exists. So this may not be the
perfect solution.
The reason for having it be a subclass of Processor::Z80 instead of
virtual functions for the MasterSystem::CPU core to define is due to
naming conflicts. I wanted the core to say `in(addr)` and have it take
the four clocks. But I also wanted a version of the function that didn't
consume time when called. One way to do that would be for the core to
call `Z80::in(addr)`, which then calls the regular `in(addr)` that goes to
`MasterSystem::CPU::in(addr)`. But I don't want to put the `Z80::`
prefix on all of the opcodes. Very easy to forget it, and then end up not
consuming any time. Another is to use uglier names in the
`MasterSystem::CPU` core, like `read_`, `write_`, `in_`, `out_`, etc. But,
yuck.
So ... yeah, this is an experiment. We'll see how it goes.
byuu says:
Changelog:
- MS: added ms/bus
- Z80: implemented JP/JR/CP/DI/IM/IN instructions
- MD/VDP: added window layer emulation
- MD/controller/gamepad: fixed d2,d3 bits (Altered Beast requires
this)
The Z80 is definitely a lot nastier than the LR35902. There's a lot of
table duplication with HL→IX→IY; and two of them nest two levels deep
(eg FD CB xx xx), so the design may change as I implement more.
byuu says:
Changelog:
- 68K: MOVEQ is 8-bit signed
- 68K: disassembler was print EOR for OR instructions
- 68K: address/program-counter indexed mode had the signed-word/long
bit backward
- 68K: ADDQ/SUBQ #n,aN always works in long mode; regardless of size
- 68K→VDP DMA needs to use `mode.bit(0)<<22|dmaSource`; increment by
one instead of two
- Z80: added registers and initial two instructions
- MS: hooked up enough to load and start running games
- Sonic the Hedgehog can execute exactly one instruction... whoo.
byuu says:
Sigh ... I'm really not a good person. I'm inherently selfish.
My responsibility and obligation right now is to work on loki, and
then on the Tengai Makyou Zero translation, and then on improving the
Famicom emulation.
And yet ... it's not what I really want to do. That shouldn't matter;
I should work on my responsibilities first.
Instead, I'm going to be a greedy, self-centered asshole, and work on
what I really want to instead.
I'm really sorry, guys. I'm sure this will make a few people happy,
and probably upset even more people.
I'm also making zero guarantees that this ever gets finished. As always,
I wish I could keep these things secret, so if I fail / give up, I could
just drop it with no shame. But I would have to cut everyone out of the
WIP process completely to make it happen. So, here goes ...
This WIP adds the initial skeleton for Sega Mega Drive / Genesis
emulation. God help us.
(minor note: apparently the new extension for Mega Drive games is .md,
neat. That's what I chose for the folders too. I thought it was .smd,
so that'll be fixed in icarus for the next WIP.)
(aside: this is why I wanted to get v100 out. I didn't want this code in
a skeleton state in v100's source. Nor did I want really broken emulation,
which the first release is sure to be, tarring said release.)
...
So, basically, I've been ruminating on the legacy I want to leave behind
with higan. 3D systems are just plain out. I'm never going to support
them. They're too complex for my abilities, and they would run too slowly
with my design style. I'm not willing to compromise my design ideals. And
I would never want to play a 3D game system at native 240p/480i resolution
... but 1080p+ upscaling is not accurate, so that's a conflict I want
to avoid entirely. It's also never going to emulate computer systems
(X68K, PC-98, FM-Towns, etc) because holy shit that would completely
destroy me. It's also never going emulate arcade machines.
So I think of higan as a collection of 2D emulators for consoles
and handhelds. I've gone over every major 2D gaming system there is,
looking for ones with games I actually care about and enjoy. And I
basically have five of those systems supported already. Looking at the
remaining list, I see only three systems left that I have any interest
in whatsoever: PC-Engine, Master System, Mega Drive. Again, I'm not in
any way committing to emulating any of these, but ... if I had all of
those in higan, I think I'd be content to really, truly, finally stop
writing more emulators for the rest of my life.
And so I decided to tackle the most difficult system first. If I'm
successful, the Z80 core should cover a lot of the work on the SMS. And
the HuC6280 should land somewhere between the NES and SNES in terms of
difficulty ... closer to the NES.
The systems that just don't appeal to me at all, which I will never touch,
include, but are not limited to:
* Atari 2600/5200/7800
* Lynx
* Jaguar
* Vectrex
* Colecovision
* Commodore 64
* Neo-Geo
* Neo-Geo Pocket / Color
* Virtual Boy
* Super A'can
* 32X
* CD-i
* etc, etc, etc.
And really, even if something were mildly interesting in there ... we
have to stop. I can't scale infinitely. I'm already way past my limit,
but I'm doing this anyway. Too many cores bloats everything and kills
quality on everything. I don't want higan to become MESS v2.
I don't know what I'll do about the Famicom Disk System, PC-Engine CD,
and Mega CD. I don't think I'll be able to achieve 60fps emulating the
Mega CD, even if I tried to.
I don't know what's going to happen here with even the Mega Drive. Maybe
I'll get driven crazy with the documentation and quit. Maybe it'll end
up being too complicated and I'll quit. Maybe the emulation will end up
way too slow and I'll give up. Maybe it'll take me seven years to get
any games playable at all. Maybe Steve Snake, AamirM and Mike Pavone
will pool money to hire a hitman to come after me. Who knows.
But this is what I want to do, so ... here goes nothing.
Tim Allen