In article <1993Jun13.174944.9099@cc.gatech.edu> byron@cc.gatech.edu (Byron A Jeff) writes:
quoted text
>In article <HAGAN.93Jun13122844@freya.cs.umass.edu> hagan@freya.cs.umass.edu (Craig I. Hagan) writes:
>>
>>   Does anyone know how I can find out the specs on the Cyrix Cache loaders?
>>   It might be useful to produce equivalences under Linux.
>>
>>i wish i knew the specs. perhaps cyrix would be willing to
>>provide both the specs, and a method for linux to recognize
>>a cyrix chip upon boot so the kernel could enable the cache.
>
>Get a copy of the July 1993 issue of ComputerCraft Magazine ( I think
>that's where I saw it). It has an article describing the performance of 
>the Cyrix parts and how to enable to caches. It should be about a 10
>line C program. I'd give the info but I can't put my hands on my copy of it.
>As I remember the enable/disable of the cache is I/O based (port 22h).

Normally for a board designed to take one of these cyrix chips, the BIOS
should enable the cache on startup. But if it's in a normal 386 motherboard
you may find the following of some use.

Ok for Linux, try something like this in either 'startup' or the initial
kernel (assembly) code: (adjust to suit your favorite assembler :)

        mov     al,     0c0h            ; Select CCR0
        out     22h,    al

        mov     al,     022h            ; Set HOLD state to Flush Cache
        out     23h,    al              ; 640k - 1M non cachable

        mov     al,     0c6h            
        out     22h,    al

        mov     al,     00h             ; Set size of non cachable region 1
        out     23h,    al              ; to zero - i.e. disable it

Note: I haven't tried any of the above, it's just from reading values
out of the databook.  There are other bits in there which control various
things some of which are only appropriate to purpose built motherboards.

Something that you may require is the ability to set the non cachable regions,
there are four of them. They can to a size of 4k multiplied by powers of two,
and based at any 4k start. May be of use if you have linearly mapped video
ram.

Hope the above is of some use,

        DF
-- 
Derek Fawcus (G7FVS)                                df@eyrie.demon.co.uk