byuu says:
Another six hours in ...
I have all of the opcodes, memory access functions, disassembler mnemonics
and table building converted over to the new template<uint Size> format.
Certainly, it would be quite easy for this nightmare chip to throw me
another curveball, but so far I can handle:
- MOVE (EA to, EA from) case
- read(from) has to update register index for +/-(aN) mode
- MOVEM (EA from) case
- when using +/-(aN), RA can't actually be updated until the transfer
is completed
- LEA (EA from) case
- doesn't actually perform the final read; just returns the address
to be read from
- ANDI (EA from-and-to) case
- same EA has to be read from and written to
- for -(aN), the read has to come from aN-2, but can't update aN yet;
so that the write also goes to aN-2
- no opcode can ever fetch the extension words more than once
- manually control the order of extension word fetching order for proper
opcode decoding
To do all of that without a whole lot of duplicated code (or really
bloating out every single instruction with red tape), I had to bring
back the "bool valid / uint32 address" variables inside the EA struct =(
If weird exceptions creep in like timing constraints only on certain
opcodes, I can use template flags to the EA read/write functions to
handle that.
byuu says:
Four and a half hours of work and ... zero new opcodes implemented.
This was the best job I could do refining the effective address
computations. Should have all twelve 68000 modes implemented now. Still
have a billion questions about when and how I'm supposed to perform
certain edge case operations, though.
byuu says:
I now have enough of three instructions implemented to get through the
first four instructions in Sonic the Hedgehog.
But they're far from complete. The very first instruction uses EA
addressing, which is similar to x86's ModRM in terms of how disgustingly
complex it is. And it also accesses Z80 control registers, which obviously
isn't going to do anything yet.
The slow speed was me being stupid again. It's not 7.6MHz per frame,
it's 7.67MHz per second. So yeah, speed is so far acceptable again. But
we'll see how things go as I keep emulating more. The 68K decode is not
pretty at all.
byuu says:
Changelog:
- moved Thread, Scheduler, Cheat functionality into emulator/ for
all cores
- start of actual Mega Drive emulation (two 68K instructions)
I'm going to be rather terse on MD emulation, as it's too early for any
meaningful dialogue here.
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