From: rohrer@fncrd6.fnal.gov (Keith Rohrer) Subject: Re: Help - Cyrix processors, anyone know for sure? Date: 17 Aug 1992 18:16:45 GMT
In article <0105010F.b54s7l@mprnews.mpr.com> mslater@mpr.com writes:
[deleted]
>It is true that the cache must be enabled by initialization software,
>but this can be done by a program (supplied by Cyrix to its OEMs)
>that in part of autoexec.bat.
Is (assembler?) source to this/such a program going to be available,
so those of us not using DOS can use it?
>The Cyrix chips have some additional signals to handle A20 masking
>and cache control, and for best performance, the hardware needs a
>small modification (a couple gates and a few wires) to support these
>signals. It is not absolutely necessary, however; the chips have software
>control registers that allow the needed functions to be implemented
>without any hardware mods, but there is a small performance hit. For
>example, without the hardware mods, the chip must make the first 64K
>of each 1 Mbyte region non-cacheable to avoid the A20 wrap-around
>problems.
I take it this is to avoid the Microsoft HMA kludge; can those of us
who use something besides DOS, or hold our right hands up and solemnly
swear not to use the HMA when we do, disable this feature?
>Michael Slater, Microprocessor Report mslater@mpr.com
>P.O. Box 2438, Sebastopol CA 95473 707/823-4004 fax 707/823-0504
Keith
(rohrer@fncrd0.fnal.gov, where all followups/replies should be sent...)
-- Disclaimer: None of Grinnell College, URA, Fermilab, and any other affiliated persons or orginizations have licensed my ideas or opinions, and thus are not entitled to any which may appear above.