TLB?

[mrbrown]

Has anyone gotten far enough to check to see the PSP's CPU supports a TLB? I had assumed it did, but then a friend pointed out this slide: http://pc.watch.impress.co.jp/docs/2005 ... igai_2.jpg

It would really suck if it didn't.

[Guest]

Has anyone gotten far enough to check to see the PSP's CPU supports a TLB? I had assumed it did, but then a friend pointed out this slide: http://pc.watch.impress.co.jp/docs/2005 ... igai_2.jpg

It would really suck if it didn't.

Depends on ones way of thinking. Were I to write an OS for an embedded device, I would try to avoid using a TLB unless I really have to. TLB is only necessary to provide any hardware assist to implementing virtual memory.

If I ever port the OS that I want to port to the PS2, you can be sure I won't be using the TLB. :P

[mrbrown]

There is no "nommu" (uClinux) port of Linux for the MIPS processor. The last one that existed was for the PS1. That means that Linux on the PSP will need a huge investment in getting the MIPS nommu port started, much less targeted to the PSP. nommu means no Linux on the PSP for a long time :P.

[Guest]

*sniff* Emotes Gorim with a tear in his eye.

:)

[blackdroid]

then go for netbsd that do have a mmu-less port :)

[rinco]

Xiptech ported uClinux to MIPS platform. We offer patch of uClinux kernel,uClibc,elf2flt and document. We also provide a software Simulator, which can run MIPS linux binary code, for people who want to learn MIPS but without real hardware. The simulator is a virtual machine, it has a MIPS R3000 CPU and some virtual hardwares, including UART,flash rom,RAM,LCD,touch screen,etc. It provides world leading performance

http://www.xiptech.com/uclinuxformips.htm

[mrbrown]

then go for netbsd that do have a mmu-less port :)

They have a MIPS mmu-less port?

[mrbrown]

Well, loser indicated that kernel RAM is protected from user access, so they would have to have at least a basic MMU in place to lock down certain sections of RAM.

Another thing he mentioned was that cop0 was unusable in user programs. So figuring out what type of MMU they have and what it can do is a bit tricky (along with many other kernel-only things).

[TyRaNiD]

Yes that does seem to be the case.

Perhaps what they meant by no TLB is you can no longer access it, I would guess (at least technically) you could access to TLB for setting up scratch pad or something in the ps2. Seems a strange thing to say though.

[Guest]

Well, without a TLB then all memory accesses are "unmapped". There can still be user, supervisor, and kernel spaces, which would be sufficient to protect the kernel from userland. The only thing is, they may need to hard code the kernel range, or set it via registers. Just a possibility of course. :)