I think the only real difference between the MMU's of the 710 and
the 720 is that teh 720 has some of the features of the SA-1100. That is
the ability to relocate teh exception vector to 0xFFFF0000 and the PID
(Process ID) register to relocated the first 32MB of the virrtual address
space to another 32MB region. These are listed as so called WinCE
enhancements and only work when the WinCE pin is active on the chip.
Refere to the ARM manuals on the chips for more detial.
Cheers Adam
On Thu, 19 Aug 1999, Dan Conti wrote:
> Hello everyone,
>
> I am working on porting linux to an arm720 chip that i am currently
> working with, and i've run into a bit of a hitch. I can build kernel
> images that work with (relatively) minimal problems (such as paging
> issues) on an arm710 chip I am working with, but i'm having difficulty
> with the 720 version. I added a mask in the ProcTypes list in head-armv.S
> for the 720 processor id, and created a new set of processor functions
> (arm720_processor_functions) to properly flush the TLB and the cache,
> since the coprocessor registers are slightly different on the 720, but i'm
> not really sure what else needs to be modified. Most of my kernel appears
> to be working, I get up to a point where the kernel attempts to open
> /dev/console (in init/main.c), at which point it falls flat on its face
> with a file not found. My setup is a bit wierd, the 720 i am working with
> is completely diskless, so the root file system is in a ramdisk, but i
> know this works (or, at least, it works on the 710 system i have). The
> root file system properly mounts.
>
> I have traced execution all over trying to track down exactly what goes
> on, but i can't exactly determine what difference between the two chips
> would allow one kernel/ramdisk image to work fully on the 710 but cause it
> to fail so late in the game on the 720. So right now i'm trying to gather
> information of any sort, if anyone has experience with 710 and 720 chips
> and provide any information or resources on casual or glaring distinctions
> between the two, i'd be really appreciative. I'm sorry if i'm a little
> vague on detail, i'm hesitant to release information regarding the
> specifics of what i'm working with.
>
> Any help would be greatly appreciated...Thanks in advance,
> -Dan
>
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