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brad-lin / FreePSXBoot

Exploit to allow loading arbitrary code on the PSX using only a memory card (no game needed)
MIT License
574 stars 44 forks source link

Exploit fails to trigger on a console upgraded to 8MB #106

Open OldBoredEE opened 1 year ago

OldBoredEE commented 1 year ago

This is pretty unusual case, but I thought it was worth reporting it in case anyone else runs into it.

Console is a SCPH-5501 (Boot ROM CRC = 8d8cb7e4) that's been expanded to have 8MB of main memory - on this console, going to the memory card screen with the FreePSXBoot memory card installed does nothing - it just displays the card as being blank. The card is working normally on another SCPH-5501 with the same boot ROM, but the original stock 2MB RAM. I guess something the exploit is relying on memory aliasing.

nicolasnoble commented 1 year ago

Yes, some versions of the exploit explicitly relies on the two address bits missing to roll over into kernel space. This indeed won't work on a modified console for which the bios requires this, as it'll hit upper ram instead of the kernel space.

JMaxxL commented 1 year ago

Is this the Asia VCD console ?

OldBoredEE commented 1 year ago

Is this the Asia VCD console ?

No, it's regular SCPH-5501 retail NTSC:U/C unit - it's just had the RAM chips replaced with larger ones to expand the total memory to 8MB to match the memory on the development boards.

The SCPH-5903 has the same 2MB RAM as other retail consoles.