Playstastion 2 classic BIOS mod. Would it be feasible?

I have this question for a while, if a bios mod/swap would work for the classic PS2 models, in a similar manner like the Sega CD / Dreamcast mods work.
I'm interested to see if the dev/debug or the PSX DESR 7700 bios can be modded to a 55xxx series PS2 unit.

 

There is no need, modchips works on PSX anyway. Don't know if it's boot at all with 5xxxx BIOS on board.

 

I don't own a PSX, I'd like to use its bios on a regular retail unit though.

 

It's not really a BIOS because it doesn't provide basic I/O. All the code on it does is to handle boot up (may involve board-specific stuff) and then boots the browser. The browser is a program that resides in ROM. It may attempt to locate and to boot an update, except for the R-chassis SCPH-90000 that has no capability to boot an update from memory cards.

Replacing the ROM chip will likely cause a boot failure, due to the normal CEX board not having the PSX's hardware (i.e. it does not have 64MB RAM nor the DVRP). Also because boot certification (unlocking) of the CD/DVD drive will fail due to the ROM version number mismatch.

All DRM is done in the hardware. So DEX (DebugStation, which are used to test titles and have no debugging capabilities) and TOOL (development) units are physically special as well. DEX consoles have a ROM that is nearly almost like a CEX's too, other than changes to support the hardware differences (i.e. no support for encrypted files, no support for DVD Video reading, region-free PS2 logo program).

So it may be possible to bring the XMB over to the CEX PS2 because the core hardware functions nearly exactly the same, but it may involve a lot of hacking to get it to not expect the DVR functionality. The XMB is actually stored on the PSX's HDD, which is why a dead HDD = bricked PSX.

 

SP193:
Maybe it may not work on a PSX, but this might be a good way to "downgrade" newer "R-chassis" SCPH-90000 consoles.

Wish I had one to experiment with since I do have a donor board to take a 2.20 ROM from (I think the SCPH-77000 onwards use 2.20 until the 8d datecode 90000) and I have the tools to remove both ROMs - simply heat up the pin and slightly bend it upwards using a thin paperclip. I also have a FMCB card handy to test if the board will accept memory card updates.

I might hunt down one just for the sake of it, and do some research on it.

 

Swapping the ROM is difficult (compared to installing a modchip), which is probably why it isn't a method that is widely discussed.

But in all seriousness, it may not totally work because of boot certification. The R-chassis ROM is v2.30, while the P chassis is v2.20. This version number, along with the ROM type (whether it was for a CEX, DEX or TOOL) and region will be passed to the MECHACON for boot certification.
Unless you don't mind losing the CD/DVD drive. But that may cause any software that waits for it to become ready to simply not work right, as the drive will never become ready.

 

I'm pretty much meaning a swap between CEX machines and of the same region - i.e PAL 2.20 ROM on PAL 2.30 ROM machine.

 

The version number is passed too. Unless it isn't a factor in boot certification, despite the fact it is part of the data sent in boot certification.