forums.ps2dev.org

In a couple of places, I've read that the iop doesn't have a mmu/tlb, and that the virtual address space is fixed to be the entire physical address space. It isn't possible to remap stuff as you normally would with a mmu.

However, some docs about the ps1 cpu go into some detail about the tlb. In addition, I was looking at the bios for the ps2, and some of the code for the iop writes to entrylo/entryhi, and calls tlbwr, signs of it having a tlb.

So what gives? Is the tlb just stripped down/lacks most features, or is the tlb on the iop differant from the tlb on the r3000a in the playstation 1?

As far as I know, the IOP does not have a TLB in any form.

Maybe if you could specify what IOP code in the BIOS you have seen using TLB related operations, we could get to the bottom of this :-)

Hm I made a mistake. It was just writing 0 to those registers, which I didn't notice until now. I'm assuming that the psx doc by Joshua Walker is wrong when it goes in depth on the tlb. However, I once saw something about some company that ported Linux to run on the psx. How did they do that if it doesn't have an operational tlb?

It was probably uclinux, which is linux specifically designed to work on systems without an MMU.

http://en.wikipedia.org/wiki/Runix

PSXLinux (also known as Runix) is a Linux kernel and development kit for the PlayStation (MIPS-NOMMU). PSXLinux is based on the μClinux 2.4.x kernel (www.uClinux.org) and contains specific support for the Sony PlayStation.

Thanks. Runix looks interesting, I'll have to play around with it some day.