Hacker News new | ask | show | jobs
by spicyjpeg 12 days ago
On the PS1 it's actually slightly more complex than that. The CPU does support up to 16 MB of main RAM (development kits and PS1-based arcade systems did come fitted with more than 2 MB) and has a register to configure its geometry, with the CPU automatically generating an exception when attempting to access unmapped memory. However, Sony's BIOS made the mistake of initializing said register to 8 MB (the configuration used by dev boards) even on retail hardware, resulting in the 2 MB region being mirrored four times. Development builds of games typically assumed 8 MB and put the stack at 0x80800000, so the accidental mirroring made that setup work on retail hardware too (at least as long as the stack did not collide with the heap) even if the developer forgot to move the stack down in the final build.

[1] https://psx-spx.consoledev.net/memorycontrol/#1f801060h-ram_...
1 comments
jbreckmckye 11 days ago
The PSX BIOS code sounds like a disaster. Everything I read about the software part of the stack, makes me amazed the console even boots

The faulty malloc. A bunch of random qsort implementations. Reiji Asakura wrote an account of how the BIOS and kernel were developed, and it sounds so amateurish

Then there's the way the JP console checks for faulty ECCs on sectors 0..15, not as a clever anti piracy check, but because the CDU-920 broke CD-XA authoring...

link
boricj 11 days ago
If you want a good horror bedtime story, you can peek at OpenBIOS within the pcsx-redux tree: https://github.com/grumpycoders/pcsx-redux/tree/main/src/mip...

The commentary section starts with "The retail PlayStation BIOS code is a constellation of bugs and bad design." and it gets worse after that. There are hidden gems inside the source code comments of that simili-reconstruction.

link