On 5/25/24 22:03, Maciej W. Rozycki wrote: > On Sat, 25 May 2024, Chuck Guzis via cctalk wrote: > >>> 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. > > 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. > 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
