jmk wrote: >If you keep the 486 then there is no point in removing the 386, >you would gain nothing.
Just to clarify exactly what the differences are, the 486 added: * Integrated floating point (and better IEEE 754 conformance) * CR0.WP control bit -- allows copy-on-write paging strategies even for accesses from ring 0 (386 didn't honor page write protection when CPU was in kernel mode) * New instructions: * BSWAP * CMPXCHG * XADD * INVD * WBINVD I agree with jmk that Plan 9 would be unlikely to gain much, since: * Plan 9 on the 386 already requires a 387, and Plan 9 is not pedantic about IEEE 754 * Historically Plan 9 has not been concerned with the kind of pedal-to-the-metal optimization that would benefit from CR0.WP, BSWAP, CMPXCHG, or XADD. * There is rarely any good reason to use WBINVD, and almost never a good reason to use INVD (except maybe in the BIOS), since x86 systems are cache coherent.
