On Tue, 2002-02-05 at 12:46, Steven J. Hill wrote: > Hartvig Ekner wrote: > > > > You have to distinguish between physical and virtual memory. The MIPS32 > > architecture supports implementations with up to 36 bits of physical > > address space, however the virtual address space in kernel and user mode > > is as you describe below. > > > I wasn't talking about the MIP32[tm] cores specifically, I was using a > generalization of 32bit. However, this is good to know. All of the data > sheets that I just downloaded from the MIPS site for the R4k[X] cores > don't mention the 36-bit PA item. Care to elaborate? > > > One note: Many MIPS32 implementations choose not to implement all 36 PA > > bits, but limit themselves to 32 bits. This saves a few bits in the TLB > > and a few address lines. > > > So, if someone did want 36 PA bits on Linux, the TLB exception handlers > and a little of the page table construction/management code would have to > change. The userspace contraints and such would still remain. Cool. I'm not sure if it's a "little" though. Ralf has already done the work for 64bit memory support on 32bit kernels, but that only works currently on 64bit CPUs. I started hacking on the 64bit memory patch to get it to work on 32bit processors, but had to put that aside for a few weeks. I hope to get back to it soon. Pete
