NOCASH PSX-BIOS SWAP

[fulas]

Hello to all members and thanks for this great site.
I'm attempt to add a second BIOS to a my PSONE scph-102, thanks Nocash for his awesome work , and of course I have a few questions:
1.As far as I know the PSONE ,and old ones, has a Rom that is organized as 512K by 8 bits, I'm planning to use a ATMEL 27c040-15rc in soic package like the psx mount. Here is a picture already soldered

The timing access is less than 70ns Would this be a problem with the psx timings?
2.On Board Programming ,I know that this eeprom needs "Hight Voltage" 12v to programming operation and for Identifier bytes reading, I am planning to solve this problem by a "diode capacitor voltage multiplier" and of course some transistors to swap VPP 12v an VCC 6.5v to normal mode.
And here it's the real problem , I have to run the original bios and load an application to program the nocash bios, Is there a way to disable the original bios once the app it's already running?

[nocash]

That http://i68.tinypic.com/23stbpc.jpg photo is showing... a PROM ??? That chip isn't even UV-eraseable, so you have only one single attempt to get the programming logic right, not to mention the programming voltages. Well, good luck with it - but I have some doubts, to say the least. Using a similar FLASH memory chip would be better & easier.

NB. For older PSX consoles (those with expansion port), the next no$psx version will include a PSX-BIOS clone that can be installed on expansion ROMs (eg. in Datel or Xplorer cheat devices). So one will be able to use the whole kernel & user interface without soldering. I'll only need to get around to release the update... which I am planning so for quite a long time (but, as usually, I am stuck with a "few final details").

[fulas]

That http://i68.tinypic.com/23stbpc.jpg photo is showing... a PROM ??? That chip isn't even UV-eraseable, so you have only one single attempt to get the programming logic right, not to mention the programming voltages. Well, good luck with it - but I have some doubts, to say the least. Using a similar FLASH memory chip would be better & easier.

It is not erasable?
You are right, I have to find other one, with soic package.

[fulas]

Well this picture is from other Psone, it's wired to work like Action replay/Gameshark....


It is not so elegant as the first post but have erase option
I have a few 29f040b that I will wire with your schematic

Code: Select all

Nocash PSX-BIOS Connection (required)

  A0..A19 (ROM) --------- A0..A19 (EPROM)
  D0..D7  (ROM) --------- D0..D7  (EPROM)
  /BIOS (CPU.97)--------- /CS  (EPROM.22)
  /OE (ROM.24)  --------- /OE  (EPROM.24)
  +5V (BOARD)   --------- VCC  (EPROM.32)
  GND (BOARD)   --------- GND  (EPROM.16)
  /CS (ROM.22)  --/cut/-- /BIOS (CPU.97)
  /CS (ROM.22)  --------- +5V  (BOARD) (direct, or via 100k ohm)

I going to write it first with Nopsx Bios and then solder to Psone.

[rama3]

I'll only need to get around to release the update... which I am planning so for quite a long time (but, as usually, I am stuck with a "few final details").

Very excited about this. Can't wait ;p

[fulas]

I have another question to Nocash, your bios/file, PSX-XBOO.ROM, is 256 kb lengh What do I have to do with the rest,512kb, of the flash ? fill with FF perhaps ?
And how about using the upper memory flash, A18, for gameshark,action replay.... purposes?
Would be realy nice job, of course if Psone doesn't needs this space for bios access.
One more question , why the IC102 (bios) needs A19 for adressing 512kbytes? IT's not enough with a1-a18 bus?

[nocash]

A19 would be for 1Mbyte chips (the SCPH-5903 actually has that much memory, probably because two teams worked on developing that console, and each wanted to have their "own" 512Kbytes of memory (technically there has been no good reason for using that much memory)).

For a 512Kbyte chip, store the 256Kbytes twice in there (needed since the font is expected in the upper half).

With a 256Kbyte chip (what you seem to have in the 2nd photo), just store the 256Kbyte in it (and the font will be automatically mirrored to the higher memory addresses).
That chip is mapped as in cheat devices? With the chipselect wired to the expansion area select line, instead of the bios area select line? That won't work with current bios clone version (and probably also won't work in next version - unless you have reproduced the whole cheat device hardware, including the I/O ports for the DB25 connector etc).

[fulas]

That chip is mapped as in cheat devices? With the chipselect wired to the expansion area select line, instead of the bios area select line? That won't work with current bios clone version (and probably also won't work in next version - unless you have reproduced the whole cheat device hardware, including the I/O ports for the DB25 connector etc).

Yes is wired to pin 98 CPU CS0 was only for put an example, the one who I'm working now goes to pin 97 CPU CS2.

[fulas]

It's working YESSSSSSSSSSS¡¡¡¡¡¡¡¡¡¡¡
At a moment I can switch original and nopsxbios by joining CPU.97 CS2 to any CHIP SELECT roms.
The flash that I has used is a 29f040 512kb, like Nocash told me:

With a 256Kbyte chip (what you seem to have in the 2nd photo), just store the 256Kbyte in it (and the font will be automatically mirrored to the higher memory addresses).

That's mean that I have the upper flash free to use with external rom (gameshark ,gamehunter,unirom and so.....), I already cut the a18 address line and still working , now I need some Glue Logic to avoid conflicts with the CS0 and CS2 signals.
Thanks you again Nocash you are GREAT¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡
Nopsxbios running in a real Psone

[youtube]http://www.youtube.com/watch?v=LzzOYx457NI[/youtube]

[danhans42]

Just a quick question on this if you could help noca$h

I have seen this thread over on assemblergames...

There is a cheat device that just piggybacks the BIOS rom..

https://www.assemblergames.com/threads/ ... mod.66268/

how would I go about hooking up a flash rom to my PSone? I get the address/data lines, its just the CS/OE/WE lines that I am stuck

The board in the eBay listing is bare other than the flashrom and the PIC, so it must just be a case of wiring up correctly surely?

[nocash]

Chip select for BIOS ROM is CPU pin 97.
Chip select for Expansion ROM is CPU pin 98 (or Expansion Port pin 4).
The latter would map your ROM similar to those used in cheat cards, but of course without reprocuding their internal I/O ports, nor the weird 'paged' memory mapping used in some of that cards.

[danhans42]

Perfect, Thanks nocash.

So I have a AT29C040A which currently has Caetla on it..

So For that is it just a matter of connecting the address/data lines as per the above as per your BIOS replacement..

Code: Select all

Nocash PSX-BIOS Connection (required)

  A0..A19 (ROM) --------- A0..A19 (EPROM)
  D0..D7  (ROM) --------- D0..D7  (EPROM)
  /OE (ROM.24)  --------- /OE  (EPROM.24)
  +5V (BOARD)   --------- VCC  (EPROM.32)
  GND (BOARD)   --------- GND  (EPROM.16)

and then connecting the CS pin from the flash ROM to CPU pin 22?

[nocash]

In theory, yes, assuming that you didn't mean CPU pin 22, and that caetla uses only the first 128Kbytes of the chip, and that you've somehow removed the action replay I/O port accesses.

[danhans42]

Sorry, typo there I meant CPU Pin 98..

Thanks, ill post back with my results.

Cheers

[Armorant]

Hello.
Finaly I were able to swap BIOS too. It works fine on 9000 and 102, but one thing I need to know about PSX-BOO bios - the modchip feature.
###
Nocash BIOS "Modchip" Feature (optional)
SPU.Pin42 "data" -------|>|------ CPU.Pin149 (A20)
SPU.Pin5 "sync" ---------------- IC723.Pin17
###
It works already (5v AM29F040B that drives from 3.4V and use IC102 pads to work). Just curios if it still need to do small additional solder works to add 1N4148 diode and few wires. Thanks.
###

[Xrider]

Hello,

I have put No$psx bios (PSX-BOO) on my EEPROM.
It's boot fine but i have a problem with game pad.
It's impossible to select other thing else "Disk".

It's normaly ?
My mother board is PU-20 pal version.


Thanks

[rama3]

There is an oversight/bug with the BIOS that prevents the controls from working when the lid is open.
Close the lid and it should work

[Xrider]

Fixit !

Thanks Rama3

[Arnold101]

exist a Nocash BIOS chip?

[Squaresoft74]

You may try getting one from here.