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SubjectRe: Playstation Emu Reply to this message
Posted bytratax
Posted on12/31/03 00:07 AM

> > The use of the term "delayed" is kind of a misnomer, at least when compared to
> > delayed branches.
> Not really, any changes to the program counter are delayed for one instruction.
> > My guess is that Tekken2's
> > use truely is a bug where a register was inadvertantly used in the first cycle
> I believe it was a missing nop in the jr ra of the called function, so it was
> executing the first instruction of the next function ( IIRC it was a mfc2 ). The
> instruction at ra then uses the register & needs it to be the old value, the
> pipeline should stall but it doesn't. In theory you should count the stalled
> cycles, but then you should also count the cache misses too. AFAIK the real
> r3000 doesn't have a stalling circuit, but the derivative the PSX uses does.
> I don't think the pipelines can be advanced when a cache misses or you'd end up
> with pretty random behaviour with regards to whether instructions in the delay
> slot would be executed or not.
> smf
I think the big problem was that it is a COP2 instruction, which makes things much more interesting than any memory or register access. In this case it relies on the exact implementation of the COP2 engine.

I wonder, did Tekken2 work correctly on the PS2 in PS1 emulation mode ? The R3K CPU is the same, but I thought the COP2 engine was emulated, so I wonder if they had to hack Tekken2 .. :)

Entire Thread
Subject  Posted byPosted On
*Playstation Emu  finaldave12/16/03 02:16 PM
.*this way last opcode costs more than the first  Terry Bogard12/18/03 00:40 AM
..*Re: this way last opcode costs more than the first  Bart T.12/18/03 02:46 AM
.*Re: Playstation Emu  galibert12/17/03 02:37 AM
..*Re: Playstation Emu  finaldave12/18/03 09:59 AM
...*Re: Playstation Emu  tratax12/31/03 00:11 AM
..*Re: Playstation Emu  finaldave12/17/03 10:05 AM
...*Re: Playstation Emu  smf12/17/03 11:21 AM
....*Re: Playstation Emu  finaldave12/17/03 11:21 PM
.....*Re: Playstation Emu  Riff12/18/03 00:57 AM
......*Re: Playstation Emu  smf12/18/03 10:24 AM
........Re: Playstation Emu  tratax12/31/03 00:07 AM
........*Re: Playstation Emu  smf01/02/04 10:56 AM
........*Re: Playstation Emu  R. Belmont12/31/03 06:19 AM
.........*Re: Playstation Emu  tratax01/01/04 11:06 PM
.......*Re: Playstation Emu  ElSemi12/18/03 06:24 PM
........*Re: Playstation Emu  Riff12/18/03 09:56 PM
.*Re: Playstation Emu  Bart T.12/16/03 06:02 PM