12 Feb
2009
12 Feb
'09
11:49 a.m.
Jim Leonard wrote:
So a simple routine to try to identify the 8088 vs.
the 80c88
would look something like:
mov cx,2 ; test if following instruction will be
; repeated twice.
db 0F3h,26h,0ACh ; rep es: lodsb
jcxz Yes ; intel non-CMOS chips do not care of rep
jmp Nope ; before segment prefix override, NEC and
; CMOS-tech ones does.
It turns out my information is bad. The bug only asserts itself when an
interrupt occurs during the REP. Buggy CPUs don't continue; later ones
do. So to fix my detection code, I will increase the count in cx to
something much longer, probably f000.
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
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