Playstation CPU reversing [56k Warning]

Members research, findings and information that can be useful towards the PlayStation 1.
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Re: Playstation CPU reversing [56k warning]

Post by nocash » January 8th, 2015, 10:06 pm

Great that you are still working on that beast! I'll need to implement your findings about the MDEC formulas (when I turn back to working on no$psx, at the moment (=next some months) I am busy with dsi support for no$gb).

Yes, "Not used (should be zero)" was meant that the bits are unused and they don't affect the result. But if you are writing to that registers, then you must put something into the unused bitfields - which should be filled with zeroes (just by convention, because Sony is doing that way, and because writing other/random values would look messy). And, using zeroes might become important in case Sony would release a "MDEC+" revision that uses that bits for extra functions (of course, that's extremly unlikely for 20 years old hardware).

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Re: Playstation CPU reversing [56k warning]

Post by cybdyn » January 14th, 2015, 1:05 am

no$: can chk also about EOR/EOF bit , for example Resedent Evil 1: after last cutscene before menu, it still play xa audio. i dont know what real cd dsp/hc05 does , but i just stop play xa sound. maybe if you will find new details, add please it on tech spec about Ps1)) ?

also: don't you know, combination of (SeekL + gelocL) or (SeekP + gelocP) - so does it update loc? or head stay around one possition and loc is +/- few frames?

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Re: Playstation CPU reversing [56k warning]

Post by nocash » January 14th, 2015, 7:25 am

cybdyn wrote:no$: can chk also about EOR/EOF bit
The cdrom HC05 firmware doesn't seem to process that bits at all.
Games can process that bits on the MIPS CPU side though (but, I am not sure if that would be good idea - if the audio/video streaming is done without error correction & without read-retries, then the EOR/EOF bits might never arrive at the MIPS CPU in case of read errors - I don't know if the PSX is really streaming without error handling though).
cybdyn wrote:also: don't you know, combination of (SeekL + gelocL) or (SeekP + gelocP) - so does it update loc? or head stay around one possition and loc is +/- few frames?
SeekL/SeekP are doing seeks. It doesn't matter if you combine them with getlocL or getlocP.
And that SeekL/SeekP stuff should be described quite well in current psx-spx version, or is there anything unclear?

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Re: Playstation CPU reversing [56k warning]

Post by cybdyn » January 14th, 2015, 10:06 pm

i just thougth LC mechanism uses only combination seekl+getposP. but i see it uses read 1b.
just some games send getposP 10 times or so, after seekP, just wondring if i need update or increment pos. , or it stays on same pos, and only frame changes around last position of seeking..

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Re: Playstation CPU reversing [56k warning]

Post by cybdyn » January 15th, 2015, 8:40 pm

about EOF flag, just idea. maybe this bit make from 0x64 to 0xE4 , and we need play as xa and send as data at same time (int1) to let know mips-cpu program "this is the end"?

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Re: Playstation CPU reversing [56k warning]

Post by LostTemplar » January 29th, 2015, 8:26 am

Hey Akari, I'd like to help out more with the reversing and posted some stuff on the psxdev.ru board. Could you maybe have a look? That would be great.

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Re: Playstation CPU reversing [56k warning]

Post by Akari » January 30th, 2015, 6:44 am

LostTemplar wrote:Hey Akari, I'd like to help out more with the reversing and posted some stuff on the psxdev.ru board
I upload lastest researched data to svn. Most interesting are in 00_control.odg This is core control circuits. Still don't know exactly how they works.
LostTemplar wrote:Could you maybe have a look? That would be great.
look at what?

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Re: Playstation CPU reversing [56k warning]

Post by PSXBA » May 2nd, 2015, 2:42 am

Do you plan to decap GPU, GTE, RAM and SPU later on? I think it'd be even more helpful for emulation than decapping CPU which was already pretty well known. Especially the texture cache is still mostly unknown.

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Re: Playstation CPU reversing [56k warning]

Post by Shadow » May 2nd, 2015, 3:56 am

They already decapped the GPU as far as I know. As for decapping the DRAM, I don't see any real reason to do so. The SPU might be an interesting one though if that hasn't been done already.
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Re: Playstation CPU reversing [56k warning]

Post by PSXBA » May 2nd, 2015, 5:32 am

Shadow wrote:They already decapped the GPU as far as I know. As for decapping the DRAM, I don't see any real reason to do so. The SPU might be an interesting one though if that hasn't been done already.
Could you give me a link to this decapped GPU code? I only see CPU and MDEC in this thread.

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Re: Playstation CPU reversing [56k warning]

Post by Shadow » May 2nd, 2015, 5:45 am

PSXBA wrote:
Shadow wrote:They already decapped the GPU as far as I know. As for decapping the DRAM, I don't see any real reason to do so. The SPU might be an interesting one though if that hasn't been done already.
Could you give me a link to this decapped GPU code? I only see CPU and MDEC in this thread.
http://board.psxdev.ru/topic/7/
Development Console: SCPH-5502 with 8MB RAM, MM3 Modchip, PAL 60 Colour Modification (for NTSC), PSIO Switch Board, DB-9 breakout headers for both RGB and Serial output and an Xplorer with CAETLA 0.34.

PlayStation Development PC: Windows 98 SE, Pentium 3 at 400MHz, 128MB SDRAM, DTL-H2000, DTL-H2010, DTL-H201A, DTL-S2020 (with 4GB SCSI-2 HDD), 21" Sony G420, CD-R burner, 3.25" and 5.25" Floppy Diskette Drives, ZIP 100 Diskette Drive and an IBM Model M keyboard.

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Re: Playstation CPU reversing [56k Warning]

Post by PSXBA » May 2nd, 2015, 6:51 am

These are just pictures where is an actual code like the the code available for CPU and think GTE on Github.

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Re: Playstation CPU reversing [56k Warning]

Post by Akari » May 2nd, 2015, 3:27 pm

PSXBA wrote:These are just pictures where is an actual code like the the code available for CPU and think GTE on Github.
Only photos of top level metal is available. This is not enough to start reverse of GPU. If you are interested we can asc our decaper to polish metal and take photo of M! and then polysilicon level.

By the way - I resume MDEC reversing process after few month of Xenogears sprite algorythm reversing )

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Re: Playstation CPU reversing [56k Warning]

Post by PSXBA » May 2nd, 2015, 8:06 pm

Akari wrote:
PSXBA wrote:These are just pictures where is an actual code like the the code available for CPU and think GTE on Github.
Only photos of top level metal is available. This is not enough to start reverse of GPU. If you are interested we can asc our decaper to polish metal and take photo of M! and then polysilicon level.

By the way - I resume MDEC reversing process after few month of Xenogears sprite algorythm reversing )
Yes I am very interested thank you. Also do you plan to ever go back to GTE reversing, judging from the ogamespec/pops-gte repository it seems to be still incomplete.

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Re: Playstation CPU reversing [56k Warning]

Post by Akari » May 3rd, 2015, 4:31 pm

PSXBA wrote:Also do you plan to ever go back to GTE reversing, judging from the ogamespec/pops-gte repository it seems to be still incomplete.
Noone ever tried to reverse CPU GTE. Org wanted to do this but he seems to be busy now. Pops-gte is his project too, I dont know if he ever will work on it again.

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Re: Playstation CPU reversing [56k warning]

Post by nocash » May 4th, 2015, 2:17 am

PSXBA wrote:Do you plan to decap GPU, GTE, RAM and SPU later on? I think it'd be even more helpful for emulation than decapping CPU which was already pretty well known.
The current theory is that the GTE is part of the CPU.
But the CPU is huge, and at the moment, Akari and org are having analyzed the MDEC section only.

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Re: Playstation CPU reversing [56k warning]

Post by Akari » May 4th, 2015, 3:28 am

nocash wrote:
PSXBA wrote:Do you plan to decap GPU, GTE, RAM and SPU later on? I think it'd be even more helpful for emulation than decapping CPU which was already pretty well known.
The current theory is that the GTE is part of the CPU.
But the CPU is huge, and at the moment, Akari and org are having analyzed the MDEC section only.
Only this part of cpu has been analised to date. A lot of unknown area still left untouched.

Image

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Re: Playstation CPU reversing [56k Warning]

Post by cybdyn » May 4th, 2015, 5:54 pm

no$ : i found game like "Felony 11-79", whant it plays interleved xa stream from cd , it doesnt send any SetFilter command (to setup file/channel), and to play cdxa stream it uses mode = 0x40 (adpcm enable), the xa stream consist of 4 interlived files, not channels! ususally games use file...

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Re: Playstation CPU reversing [56k warning]

Post by PSXBA » May 5th, 2015, 4:44 am

Akari wrote:
nocash wrote:
PSXBA wrote:Do you plan to decap GPU, GTE, RAM and SPU later on? I think it'd be even more helpful for emulation than decapping CPU which was already pretty well known.
The current theory is that the GTE is part of the CPU.
But the CPU is huge, and at the moment, Akari and org are having analyzed the MDEC section only.
Only this part of cpu has been analised to date. A lot of unknown area still left untouched.

Image
I see so GTE will be decapped sooner or later, but could you analyze the GPU too, that'd be invaluable.

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Re: Playstation CPU reversing [56k warning]

Post by TriMesh » May 5th, 2015, 3:41 pm

nocash wrote:
PSXBA wrote:Do you plan to decap GPU, GTE, RAM and SPU later on? I think it'd be even more helpful for emulation than decapping CPU which was already pretty well known.
The current theory is that the GTE is part of the CPU.
But the CPU is huge, and at the moment, Akari and org are having analyzed the MDEC section only.
I think it's pretty much certain that the GTE is inside the CPU - the MIPS coprocessor interface is quite complicated, and none of the signals are present on external pins of the PSX CPU. In addition to this, mtc/mfc don''t generate any bus cycles, so you can't even sniff what's going on externally and emulate it.

I'm also pretty sure that the big block diagram of the PSX that Sony used in their early developer presentations had the GTE drawn as part of the CPU block, but I can't seem to find a copy of it online to check.

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