jkg@gitpyr.gatech.EDU (Jim Greenlee) (01/18/87)
In article <755@vaxb.calgary.UUCP> radford@calgary.UUCP (Radford Neal) writes: >Anyway, I've actually used both 68000 and 68008 processors, and can assure >you that they are pretty much compatible. According to the documentation, >they even went so far as to have the 68008 trap word accesses at an odd >address (I didn't actually try it). Personally, I think this was going >too far, especially as (I am given to understand) the 68020 doesn't. (I >know, I know, the 68008 came earlier...) My understanding of why this was done was to ensure that the 68008 would be COMPLETELY software compatible with the 68000, the idea being that at some future date you might want to *upgrade* from an (old, antiquated) 8 bit architecture to a (new, futuristic) 16 bit uP. Obviously, you wouldn't want to have to rewrite your software to handle even-only addressing, so... Actually, I think it was probably done that way to save the Motorola people the trouble of rewriting most of their micro-code. I don't know about the 68020, never having used it myself. Jim Greenlee -- The Shadow...!{akgua,allegra,amd,hplabs,ihnp4,seismo,ut-ngp}!gatech!gitpyr!jkg Jryy, abj lbh'ir tbar naq qbar vg! Whfg unq gb xrrc svqqyvat jvgu vg hagvy lbh oebxr vg, qvqa'g lbh?!
pwv@fluke.UUCP (01/24/87)
>In article <755@vaxb.calgary.UUCP> radford@calgary.UUCP (Radford Neal) writes: >>Anyway, I've actually used both 68000 and 68008 processors, and can assure >>you that they are pretty much compatible. .... > In article <2899@gitpyr.gatech.EDU> jkg@gitpyr.UUCP (Jim Greenlee) writes: >My understanding of why this was done was to ensure that the 68008 would >be COMPLETELY software compatible with the 68000, ..... Actually, I remember hearing from a Motorola "Technical" guy when the 68000 had just come out that the 68000 and the 68008 used the same die! The only difference was in chip bond-out. -- Pat Vilbrandt John Fluke Mfg. Co., Inc. Everett, Washington USA UUCP: { ihnp4!uw-beaver, ucbvax!lbl-csam, allegra, ssc-vax }!fluke!pwv ARPA: fluke!pwv@uw-beaver.ARPA