Christopher R. Bowman wrote:
> At 02:07 AM 7/2/98 , Colin Wood wrote:
> >I-Jong Lin wrote:
> >> 
> >> What does MMUITTO32, MMUDTTO32, MMUITT1, MMUDTT1 stand for and what do
> >> these values do? 
> >> 
> >
> >Where do you see these values?
> >
> I don't know where you see these, my guess would be somewhere in the pmap
> code because these look like acronyms for the Memory Management Unit
> Instruction/Data Transparent Translation registers 1 and 2.  These are
> registers on the Motorola 68040 and 68060 MMUs that allow you to set up
> special mappings that translate virtual (Motorola calls these logical)
> addresses directly to physical addresses.  This means that the physical
> address generated when a virtual address matches the TTx registers is the
> same as the virtual address.  This effect can be had using the page tables
> by making the physical address that a virtual address maps to be the same
> as that virtual address. These are good if you want to map say a frame
> buffer directly into a process or set up the kernel VM space to use
> physical addresses.  The advantage is that the page tables on not searched
> when these registers match a virtual address, and the address translation
> cache (aka TLB) is not disturbed.  The 68030 also has Transparent
> Translation registers but not seperate ones for the data and isntruction
> stream.

That was going to be my guess.  

I-Jong, I believe that the 68040 and 68030 user's guides will explain more
about these registers and what you need to do to save them.  I'm fairly
sure that gas doesn't support these registers, so you'll have to use the
actual assembled bytes to save off these registers if necessary (there may
already be an example in locore.s).  I believe that the OpenMac pages on
www.macbsd.com contain a pointer to Motorola's 68k docs library, and the
NetBSD Hardware library (on www.netbsd.org) should contain a similar
pointer.  All of the docs should be in PDF format.

I hope this helps.

-- 
Colin Wood                                 cwood@ichips.intel.com
Component Design Engineer - PMD                 Intel Corporation
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I speak only on my own behalf, not for my employer.