[Leaplist] major bug found in Linux to give root access tountrusted users...

[Bryan J. Smith]

The AMD issue didn't creep up until Intel-Microsoft pushed
2-4MiB paging to improve Intel performance.  AMD's 4KiB
paging was just as fast.

Unfortunately it introduced an unforseen cache-memory
coherency issue with the on-CPU AGPgart in the Athlon
CPU.  Intel's AGPgart is in the chipset.

Disabling it was none-too-easy in DOS 7.1 / Enhanced386
of Windows 98+.  In Linux, it was a kernel tunable.

It's extremely rare that it shows up, and almost always only
in the Athlon MP (where there are two AGPgarts).  It's mainly
an Alpha EV6 (AMD Athlon switching architecture) versus
Intel AGTL+ (Intel "hub" bus architecture) difference.

The I/O MMU in the Athlon 64 / Opteron addressed this
completely.  In fact, various improvements in the AGPgart
let to much of the I/O MMU's base design going forward.

The AGPgart in the Athlon MP can even be used as a
"poor man's I/O MMU."  There is a modified x86-64 kernel
that can execute on modified "32-bit" Athlon MP boards to
allow it to do many things "like an Opteron" (including the
native 40-bit platform addressing of EV6, which all 32-bit
Athlon's are actually capable of).



----- Original Message ----
From: Kevin Korb <kmk at sanitarium.net>

I remember hearing about AMD issues with Win9x but the only Win9x games I
have left that I care about are Red Alert 2 and System Shock 2 and both of
those run fine with it.

MS DOS OTOH had issues with CPUs > 500MHz.  Especially if you run anything
that was compiled by Turbo Pascal.  They had some kind of idle loop timer
thingie that blows its mind if the computer is too fast.

I did try some of the aspect ratio fixes with Seawolf in dosbox but none
of them helped at all.  I am surprised it doesn't work as it works fine in
a window and it is using 640x480 which is pretty standard though a little
uncommon for DOS games.

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