Hello,
I have a question our assembly people: I stumbled upon an unusual instruction
in the EDR-DOS source [1]. In RASM86 this is expressed as
XLAT CS:AL
which gets encoded as 2E D7.
So this is a CS segment override prefix for an otherwise usual XLAT
instruction. I found no way to reproduce this instruction in JWasm other than
doing the following:
DB 2eh
XLAT
The Intel documentation for XLAT explains that the value to be added to AL is
fetched from DS:BX, so probably the DS gets replaced by the CS override. But is
the override prefix valid at this point, and does this work on all common CPUs?
Intel documentation is silent about this.
Thanks,
Bernd
[1]
https://github.com/SvarDOS/edrdos/blob/d579db43a97554dcac35becf510d7be8f5a85aae/drdos/header.a86#L1250
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