PSX BIOS from PSP 6.60 optimised to play games more smoothly: but how?


#1

Hi all!

As you know it’s possible to buy and download PS1 games from Sony’s PSN service. This selection of PS1 games are playable on up to three platforms: PSP, PSVita and PS3 (which platforms exactly depends on the individual game release).

I recently read several mentions on various forums about the PSX BIOS that is included with PS1 on PSP game downloads allowing games to run more smoothly. This sounded crazy to me, but I have an open mind, so I decided to check for myself. It’s possible to extract the PSX BIOS using a hacked PSP running 6.60 CFW.

Anyway, I extracted this strange BIOS and… the claims are true! :open_mouth:

So far I’ve tried the BIOS using the following emulators:

  • POPS on PS2
  • RetroArch on SNES Classic Mini
  • RetroArch on Raspberry Pi 3

Games run more smoothly using it. :clap:

There are definite frame rate improvements, such as removal of stuttering in some games. Other more demanding games can be run in hi-res mode when using RetroArch, whereas they could not using a traditional PSX BIOS. Some games that refuse to run at all when using traditional BIOS run just fine using the enhanced BIOS.

The enhanced BIOS seems to be based, at least in part, on the “final” PSone BIOS (v4.5) judging by the plain text it contains. IDA Pro crashes when trying to open it as a PSX BIOS, so it must be quite different in some way?

So I am wondering, how has this enhanced BIOS been optimised and modified to improve performance?

Any thoughts appreciated!

Cheers,
matt

[EDITED: No links to copyrighted materials, including BIOS images]


#2

This is news to me. Interesting…


#3

Interesting,I’d love to give a try if I could have your bios ←_←

Edit:I’m smart and found it from you on another forum ^ _ ^ btw what games can run smoother? I’d like to have a test.


#4

I tried an extracted PS1 bios from a PSP and it appears your findings are correct, games that used to stutter for me run much smoother and I have able to go from 4x to 8x rendering where as before it would be unplayable.


#5

Would you mind posting how did you dump the bios? my PSP is running on 6.61 and i would like to try this out…thanks.


#6

http://wololo.net/talk/viewtopic.php?t=32416

Guide I used


#7

@RetroFans Every game runs smoother!

@Tyrr64 the guide I used: https://www.reddit.com/r/PSP/wiki/biosdump

@Clarkyk what PSP system software did you dump from? I am on 6.60, and wondering if earlier PSP system software has different PSP XBIOS?

For the more technically minded, I would love to know about how exactly this BIOS has been improved?


#8

It was from a 6.60 fw was well. Although I am beginning to wonder if it is possible to drop a PS1 bios through the Vita if that bios maybe any more different, so many possibilities


#9

Not sure what you mean @Clarkyk ?

I’ve been looking for references to this, as I can’t believe this more optimised BIOS has been hiding in plain sight for years.

Here’s the earliest one I’ve found, from 2007. It mentions that the bios has the CD player and memory card manager removed for a start.

https://www.ngemu.com/threads/bios-used-for-psx-emulation-on-psp.92778/


#10

Interesting

What’s the BIOS hash (MD5, or CRC) btw?

Did you test it with Mednafen PSX as well (he was using PCSX ReARMed btw)?


#11

Sorry if my comment through you off. I was wondering if a PS1 bios dumped though a Vita would be any different to the PSP extracted bios or not.

As for the information you dug up, seems interesting the MC manager and CD player are removed ( useless for most anyway) as I always thought some trace may have been left in case. I will have to try turning off the skip bios to see if the boot up screen loads


#12

@Clarkyk @matt Thanks!

@sergio-br2 The BIOS from my PSP:

  • CRC32: cc82b93b
  • MD5: 32c04484c234fd09d79625e9fe2ec232
  • SHA1: b8c96eefcaedd3f8ae2a58d71671364703caaa25

And another one around the web:

  • CRC32: 5660f34f
  • MD5: c53ca5908936d412331790f4426c6c33
  • SHA1: 96880d1ca92a016ff054be5159bb06fe03cb4e14

#13

I have tested it with the core, as a substitute for the eu bios, and my system it works. On my wife’s slower system (from 2007) it makes most of the games usable, but the music still stutter, but not as bad as without. Also the one I found doesn’t seem to contain a bios logo when used, you get the sound when the logo should play but no visuals


#14

I think I found the same one, as the Bios boot screen went right into the PS black bg, skipping the white Sony diamond logo, ans that is a showstopper for me; I have weakness for displaying boot screens. Havent noticed a difference with the games I tested. If you know of one or two that is noticeable, share the names.


#15

Wouldn’t it be possible for some kind of graphical blacklisting? for example, effect x doesn’t get rendered or shader y doesn’t get rendered…you know… I can’t say i saw any difference between bios’es, performance wise, maybe there’re graphical differences? I should test some games. Which games did you guys saw better performance?


#16
CRC32: 5660F34F  
XXH: 10E861C2ED0D6F4B  
MD5: C53CA5908936D412331790F4426C6C33  

I’ve only been testing on low power devices (POPS/PS2, SNESC, RPi3) so no Mednafen PSX but I’d expect the benefits to be seen there, too. The game calls the BIOS (which is optimised) so the emulator or device running the game is almost irrelevant. My dump has no white (Sony logo) boot screen but does have the black (PS logo) boot screen.

@Clarkyk ah, I see. I’m not sure about how PS1 on Vita works, but it’s definitely something that should be investigated!

@Tyrr64 mine is the one you found in the wild. I’d be interested to see how yours differs? Apart from the extra logo boot screen.

@Kondorito some that come to mind: Panekit, Kero Kero King, Ridge Racer, Pepsiman, will think of some more I saw good improvements in. (not every game will see improvements)

The only graphical differences I have found is that they seem to be rendered more quickly. I’ll be doing some benchmarking soon, will publish the results here.


#17

I’ve been trying to find a match for your MD5 and the only reference I could find is here: https://pc12.5ch.net/test/read.cgi/software/1252720638/l50

Which appears to be: System ROM version 4.5 05/25/00 J

Update: and after a bit of digging I’ve also seen it refered to as a custom POPS BIOS, so I wonder if it has been modifed to eek out a bit more performance?


#18

Hi,

I’ve also dumped my BIOS.

When starting BIOS Dumper 2.6, it gives the following info : Region : NTSC J BIOS version : 4.5 CRC32 : 5660F34F Date : 05/25/00

But when I dump the 5 parts, convert VMR to MCR and merge them I get the following .bin :

SCPHXXXX.bin CRC32 cc82b93b MD5 32c04484c234fd09d79625e9fe2ec232 SHA-1 b8c96eefcaedd3f8ae2a58d71671364703caaa25 Size 524288


#19

Issue solved ! I discovered that tool VMP2MCR (Windows) was the faulty part. Basically, if after converting the first part, you open the part 2 and click convert, the part2 input file was not loaded and part1 was still converted (into part 2). So the end-result was the 5 parts 1 were merged together. The solution was to close VMP2MCR after a part was converted and the reopen the application to convert the next part. Now I get the proper CRC32 !

So cc82b93b corresponds to the merge of 5 x part1 and 5660f34f is the proper CRC32.

@Tyrr64 I think you faced the same issue as me as you have the exact same wrong CRC32.


#20

No one is asking the important questions here lol

Is this BIOS region free, or do 3 separate versions exist? I mean, we need all 3 to get the proper boot screens with “SCEA”, “SCEE”, and “SCEJ” under the PSX logo using current BIOS. If this “is” region free, does auto region detect function, or do we have to manually set it, or (god forbid) are we stuck with it claiming to be from a singular region despite the games own?