Bell Tech W.G.E. use with "sissy" unix

[David F. Carlson]

In article <428 at eecea.eece.ksu.edu>, terry at eecea.eece.ksu (Terry Hull) writes:
> In article <438 at l5comp.UUCP> scotty at l5comp.UUCP (Scott Turner) writes:
> >Sanity check, can you even USE the W.G.E. card?
> >
> >That isn't as silly as it sounds. The driver supplied for the card maps
> >the 82786's registers into memory so they can be accessed rapidly and
> >easily. But if your system has a SRAM cache you may be in for a VERY
> >nasty surprise!  

I have used machines with several caching schemes (Intel chips and Everex
proprietary) and they always cache only memory they known about:  main mother
board memory.  If a device has a memory map in the AT bus structure *it* must
provide the dual port as there is no bus sharing per se in the AT bus.
Therefore, the WGE has dedicated space in the device memory range, 0xc0000->
0xdffff nearby the other major device memory:  your graphics memory space.

No caching is done of these areas or no polling IO would ever succeed.
(I'm pretty sure it does.  :-) DOS is no different from UNIX in this regard.)

-- 
David F. Carlson, Micropen, Inc.
micropen!dave at ee.rochester.edu

"The faster I go, the behinder I get." --Lewis Carroll