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SubjectRe: Playstation Emu Reply to this message
Posted bysmf
Posted on12/18/03 05:24 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.


Entire Thread
Subject  Posted byPosted On
*Playstation Emu  finaldave12/16/03 09:16 AM
.*this way last opcode costs more than the first  Terry Bogard12/17/03 07:40 PM
..*Re: this way last opcode costs more than the first  Bart T.12/17/03 09:46 PM
.*Re: Playstation Emu  galibert12/16/03 09:37 PM
..*Re: Playstation Emu  finaldave12/18/03 04:59 AM
...*Re: Playstation Emu  tratax12/30/03 07:11 PM
..*Re: Playstation Emu  finaldave12/17/03 05:05 AM
...*Re: Playstation Emu  smf12/17/03 06:21 AM
....*Re: Playstation Emu  finaldave12/17/03 06:21 PM
.....*Re: Playstation Emu  Riff12/17/03 07:57 PM
.......Re: Playstation Emu  smf12/18/03 05:24 AM
.......*Re: Playstation Emu  tratax12/30/03 07:07 PM
........*Re: Playstation Emu  smf01/02/04 05:56 AM
........*Re: Playstation Emu  R. Belmont12/31/03 01:19 AM
.........*Re: Playstation Emu  tratax01/01/04 06:06 PM
.......*Re: Playstation Emu  ElSemi12/18/03 01:24 PM
........*Re: Playstation Emu  Riff12/18/03 04:56 PM
.*Re: Playstation Emu  Bart T.12/16/03 01:02 PM