27 May
2024
27 May
'24
1:20 a.m.
On 5/25/24 22:03, Maciej W. Rozycki wrote:
On Sat, 25 May 2024, Chuck Guzis via cctalk wrote:
You mean the 8080 emulation mode or the CPU detection via AAD/AAM?
In my V20/V30 emulator, I first filtered out the 80186, 80286+ and then
ran the following snippet.
I think
it was indeed the way to tell NEC V20 and other x86 chips apart:
good if you wanted to make seamless use of the 8080 emulation mode).
Is this something you've actually verified? Seems to be a bit of an
urban legend. I can test it on a V20 system if you don't have one. mov dx,sp
push cs
mov cl,255
;-----------------------------------------------------------------------;
; On the NEC V20, the following 2 instructions are interpreted as ;
; ;
; clr1 cl,cl ;
; ;
; with cl = 0ffh, this results in cl = 07fh (bit 7 is cleared). ;
; on the Intel 8088/8086/80186/80286 chips, however, the code ;
; is interpreted as written, resulting in cl remaining the same. ;
; ;
db 0fh ; pop cs, but masm doesn't like it ;
adc al,cl ;
;-----------------------------------------------------------------------;
mov sp,dx ; fix stack
test cl,cl
jns Initialize4 ; if v20
This from my 1988 backup files.
--Chuck