BIOS Swap?

General information to do with the PlayStation 1 Hardware. Including modchips, pinouts, rare or obscure development equipment, etc.
dan9550
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Re: BIOS Swap?

Post by dan9550 » June 28th, 2014, 11:18 pm

Ahh i see, well after some pain staking soldering i JUST got the 9002 BIOS working in the 5502 i'll leave the dual bios stuff for another weekend haha.

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Re: BIOS Swap?

Post by dan9550 » July 22nd, 2014, 10:01 pm

So i thought i'd post a bit of a build log on my experiences doing this.

I started simply by removing the BIOS ROM from the SCPH-9002 which was less painful than i thought it would be.
Image

I then started to dissassemble the SCPH-5502 which did not go down without a bit of a fight.
Image
Image

Then i lifted the CE pin on the 5502 BIOS i forget which number that is :S
Image

Prepared the 9002 BIOS by bending its legs into place, and began to solder it on top of the existing BIOS.

So i ended up with something like this.
Image

I know its all a bit brief but yeah don't really feel like heavily documenting this at the moment, long storys hort i got the 9002 BIOS working standalone in the SCPH-5502, not sure which it didn't work soldered on top of the 5502 BIOS, i triple checked all the connections and assure you they were all there so it was probably something else i missed.

Feel free to ask any questions if you have them and check out the rest of the build images below.

https://imgur.com/a/qVapC

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Re: BIOS Swap?

Post by Shadow » July 23rd, 2014, 6:03 am

I take it these are old photos so we can see how you attempted to perform this mod, but I don't see any resistors and I don't see a single pole double throw (SPDT) switch anywhere still. Do you know how to read an electronics schematic?

I am also quite surprised that you did not rip up more than one pad under the BIOS with that horrendous screwdriver prying technique you just displayed. Please use a hot air rework station or chip quik next time.
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Re: BIOS Swap?

Post by Gradius » July 23rd, 2014, 7:13 am

What's the point in changing the BIOS ?

I can understand if it were an old BIOS, then trying something newer (up-to-date), but not the inverse.

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Re: BIOS Swap?

Post by dan9550 » July 23rd, 2014, 8:08 pm

Shadow wrote:I take it these are old photos so we can see how you attempted to perform this mod, but I don't see any resistors and I don't see a single pole double throw (SPDT) switch anywhere still. Do you know how to read an electronics schematic?

I am also quite surprised that you did not rip up more than one pad under the BIOS with that horrendous screwdriver prying technique you just displayed. Please use a hot air rework station or chip quik next time.
I assure you i was gentle, what i didn't show in that photo or mention was that i used de solder wick first to remove most the solder from the chip!

I have not tried to throw the other BIOS in with a switch yet... I will get around to it at some point though :)

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Re: BIOS Swap?

Post by muramasa » April 13th, 2018, 7:10 am

Would it be possible to swap the a NTSC-U/C bios into a NTSC-J system? Assuming that a modchip is also used to defeat the protection on the mechacon would there be any issues?

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Re: BIOS Swap?

Post by LameGuy64 » April 13th, 2018, 12:21 pm

I did a BIOS swap of an SCPH-7000 with an SCPH-7501's BIOS and it worked. It does eliminate the license data check but the PlayStation screen will still say SCEI as that string is stored inside the HC05.
Please don't forget to include my name if you share my work around. Credit where it is due.

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Re: BIOS Swap?

Post by muramasa » April 14th, 2018, 3:31 am

LameGuy64 wrote:
April 13th, 2018, 12:21 pm
I did a BIOS swap of an SCPH-7000 with an SCPH-7501's BIOS and it worked. It does eliminate the license data check but the PlayStation screen will still say SCEI as that string is stored inside the HC05.
Awesome good to know. The other thing I'm wondering about is if different BIOS revisions have different advantages from each other. Are there any BIOS versions that are clearly better then other versions?

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Re: BIOS Swap?

Post by postal2201 » April 28th, 2018, 4:11 pm

My BIOS Mod. Allows you to install any firmware without soldering. Maybe someone will be interested ;)
PCB in format DipTrace.
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Re: BIOS Swap?

Post by Ceros » May 23rd, 2018, 1:55 am

LameGuy64 wrote:
April 13th, 2018, 12:21 pm
I did a BIOS swap of an SCPH-7000 with an SCPH-7501's BIOS and it worked. It does eliminate the license data check but the PlayStation screen will still say SCEI as that string is stored inside the HC05.
Okay this is interesting. I am going to be doing this pretty soon too but I am still waiting on the consoles to arrive. Can you maybe elaborate on this? Perhaps send me a couple of schematics, diagrams, all that stuff? I am not new to hardware programming and modding (and soldering for that matter) but I have only been recently introduced to the PS1 and I have no idea how to analyze the BIOS binaries so that I can get all the information.
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Re: BIOS Swap?

Post by LameGuy64 » May 23rd, 2018, 12:05 pm

I just desoldered the SCPH-7000's BIOS chip and then soldered on the BIOS chip from a 7501, no special mods or wiring jobs needed. I did the BIOS ROM swap mainly to eliminate the license data check which the Japanese BIOSes in earlier models have for some reason.

Not very sure about using your own EEPROM chips to use as a BIOS ROM for the console as I've not had any experience with that.
Please don't forget to include my name if you share my work around. Credit where it is due.

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Re: BIOS Swap?

Post by Ceros » May 23rd, 2018, 7:06 pm

LameGuy64 wrote:
May 23rd, 2018, 12:05 pm
I did the BIOS ROM swap mainly to eliminate the license data check which the Japanese BIOSes in earlier models have for some reason.
Yeah exactly, circumventing that second region lock. But it is cool to know that slightly newer BIOSes are compatible with slightly older hardware. Means that there were no big hardware revisions around those parts that made it function differently. I wasn't too aware about this and since I am still waiting on them I cannot open them up and inspect them. I wish there were some schematics of the MOBO designs.
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Re: BIOS Swap?

Post by rama3 » May 24th, 2018, 12:48 am

Yep, I often swap BIOS chips from broken PAL units into working NTSC-J ones.
So far every swap worked.
I try to use donors that are at least close to the target hardware.
A 5500 unit will get a 5xxx chip, a 7000 will work with a 9002 chip but it'd be better to find a 7502 or 7002 chip.

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Re: BIOS Swap?

Post by Ceros » June 19th, 2018, 8:44 pm

rama3 wrote:
May 24th, 2018, 12:48 am
Yep, I often swap BIOS chips from broken PAL units into working NTSC-J ones.
So far every swap worked.
I try to use donors that are at least close to the target hardware.
A 5500 unit will get a 5xxx chip, a 7000 will work with a 9002 chip but it'd be better to find a 7502 or 7002 chip.
Okay so theoretically speaking, what if i have a japanese system with an american bios? Do I need to get the american version of a modchip or the japanese?
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Re: BIOS Swap?

Post by rama3 » June 20th, 2018, 6:31 am

Modchips unlock the Mechacon, so you need a Japan version chip. Has nothing to do with the BIOS.

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Re: BIOS Swap?

Post by Squaresoft74 » September 3rd, 2018, 11:58 pm

Hello,

I've just swapped a 1002 bios into a PSOne 102 just for fun and it seems to work fine so far.
Should i still use a Onechip to mod it ?

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Re: BIOS Swap?

Post by rama3 » September 5th, 2018, 2:52 am

Funky! :p

Yes, you can use Onechip, but don't solder the 2 BIOS wires.
You replaced the BIOS with a version that doesn't have the security check, so the BIOS patch is not required and wouldn't work anyway.

I wonder if there's any compatibility issues with some games.
Look out for memory card read / write failures. This is the most likely point of failure I can think of.

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Re: BIOS Swap?

Post by Squaresoft74 » September 7th, 2018, 11:29 pm

Thank you.
I'll make deeper testing when i can and will report here. :)

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Re: BIOS Swap?

Post by rama3 » September 8th, 2018, 6:01 am

Great, and how about using that 102 chip in the 1002 machine?
That would be quite interesting as well ;)

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Re: BIOS Swap?

Post by Squaresoft74 » September 8th, 2018, 9:05 pm

I grabbed a batch of 1002 consoles for part and planned to try that aswell. :D

Ultimatly I want to have an upgraded 1002 console that has:
- A KSM-440 BAM drive / done
- A power supply from a 7k-9k or one of these / done
- A bios from a 7002-7502-9002 / to do

Would a Stealth V2.8a modchip still work with such bios or should i use something else ?

And how about with the 102 bios if that works at all in the 1002 ?

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