7 Sep
1999
7 Sep
'99
8:37 a.m.
The 8088 and 8086 are actually very similar
processors. The main
difference is the external data bus width -- the 8086 has a 16 bit
external bus and the 8088 has an 8 bit external bus. I seem to remember
that the internal instruction queue is a different size on the 2 chips
but I would have to check.
The 8086 prefetch que is 6 bytes and the 8088 is 4 bytes, this is to keep
it from beating up the bus.
It is therefore difficult to tell the chips apart in
software and a lot
of 'machine info' type utilities report finding an 8088 even on
8086-based machines.
Nearly impossible. the only test I know is to compare transfer speed to
known clock. the 8086 comes up about 10-20% faster for a given clock
and memory speed. Plugging in a V20 can fool that test (you can test for
V20 instuction extensions for that).
IMHO the only reliable way to know what CPU you have
is to read the
markings on the chip package.
If they havent been sanded off or they are v20/V30s!
Allison