3 ms·
They probably could, but it would have had a large silicon cost for 1980 without performance benefit. That and ISA incompatibility.
by vardump 9y ago
They probably could, but it would have had a large silicon cost for 1980 without performance benefit. That and ISA incompatibility.
- codedokode 9y agoAdding an interrupt delay is also not free and requires changes on hardware level. But if it was done in 80s then of course it was a safe hack because there was no kernel and user mode isolation at that time.
- hyperman1 9y agoThe cost would not have been very big. The 8086 had microcode, and there were the very similar LDS and LES instructions. There were plenty of unused slots in the opcode table so that wasnt it the reason either. There are weird instructions aplenty like XLAT or AAA/AAS/AAD/AAM, so it wasnt as if they had a pressing silicon shortage. Maybe they dindt think about it, and fixed it with a quick hack once they got aware of the problem? The whole segment register story was very hacky from the start. Intel might have dumped the segment registers in i386 32 bit protected mode, as they cleaned up a lot of other troublesome corners around that time. But, well, they didn't, so we have to deal with it today.
- ithkuil 9y agoThey also had a more recent chance to clean up this with the which to 64 bit
- yuhong 9y agoThe fun thing is the 286 didn't fix this either. This is why the MOV SS came first (in protected mode the selector may not be present for example). This was a problem for DOS where SS was often used to access the DOS data segment.