Hi, On Mon, May 05, 2003 at 06:27:05PM -0400, Nathanael Nerode wrote: > After the 486, Intel always provided a method to determine the CPU type and > features available. As far as I can tell, there's no easy programmatic way > to tell the difference between a (old, no CPUID) 486 and an (old, no CPUID) > 386 without risking an illegal instruction, which bites. :-( (I could be > wrong.)
They exist and are not so difficult. One is by issuing illegal instructions like you have commented, the only thing to do is to trap INT 6 (Invalid Opcode). The only problem you may find is that really old cpus don't support this INT (only 80186+). The other is a little bit more fun, you have to test for cpu specific non-documented behaviour, like how many bits shift a shl in a 8088 or 80186+, when does the cpu increment the sp (stack pointer) when doing a push/pop, which flags can or cannot be set, etc. I did some years ago asm code that distinguished from 8088 to the new CPUID aware cpus, including the distinction from 8086 and 8088, or from NEC V20 among others. =P And I've seen code that did more insight testing. (I can give code / pointers to anyone interested). regards, guillem
