gnu@l5.uucp (John Gilmore) (12/11/85)
In article <2207@gatech.CSNET>, noman@gatech.CSNET (Jeffrey L. Grover) writes: > In article <373@amiga.amiga.UUCP>, bruceb@amiga.UUCP (Bruce Barrett) writes: > > Well, IBM has had practice with this sort of thing...The IBM > > XT/370 emulated a 370 by re-microcoding 1 (or 2??) 68000's and an 8087 > > (for floating point). > yep, IBM put 2 68000's in the XT/360 > 1. microcoded to execute as a 360 > sans floating point operations > 2. microcoded as a floating point > co-processor That's not quite true. One 68000 was re-microcoded to run most of the 360 instruction set. The other 68000 was a straight-out-of-the-box 68000, running 68000 assembler language, that implemented the less common 360 instructions by emulation. A third chip was an Intel 8087 specially modified to run IBM-format floating point rather than IEEE float. At first a lot of people thought there was great promise in the XT/370, but virtually nobody outside IBM data centers has bought them, because the software is exhorbitantly expensive, and it comes on 9-track magtapes. (What does Assembler H rent for, per month, these days? Certainly hundreds of dollars...) If you've bought or rented the software for your mainframe, you can sublicense it for your XT's; but if you haven't...