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Comment by orionblastar | Hacker News Reader

I wonder if the Commodore 128 had an Intel 8088 instead of a Zilog Z80 coprocessor if MS-DOS mode would have made it more popular?

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It had a Z80 because CP/M was popular. They had a CP/M cartridge with a Z80 inside it, but it didn't work so Bil Hurd stuck the Z80 right in the machine instead (where it then became integral to patch up some other problems on starting the thing)

If it didn't have a Z80 it would have had nothing else instead.

If they decided on MS-DOS compatibility instead, if it sold well or not would depend on how cheap it was to compete with the rest of the clone market. No matter what it would have been a "stopgap" machine since things were moving so fast back then.

Intel CPUs were significantly more expensive than a Z80. Also, many programs made for the IBM PC accessed the hardware directly, and the C128 wasn't hardware-compatible at all.

A few other companies did make early IBM-PC clones which weren't 100% hardware compatible, and that didn't go well for them.

Well the Z80 was firstly an Intel "CPU" clone. It was not yet called a CPU but a microprocessor. That said it was still a cheaper retro-engineered clone of the Intel 8080.

NEC V20 was already available, Commodore shipped Siemens 8088 in PC10/20, plenty of cheaper Asian clones at the time. Hell, if we are imagining alternative impossible reality where Commodore had competent engineers C128 could have had V20 running under 8502 hypervisor emulating PC hardware.

Those processors where binary compatible I think. And the MSX computers (Z80) haf CP/M which was very similar to MS DOS

The z80 was "compatible" with the 8080, but I think the 8088 was a variant of the 8086, which I think used slightly different registers. They described it as "source compatible".

The main difference was that the 8086 had a 16-bit data bus while the 8088 had an 8-bit data bus, requiring two cycles to transfer 16 bits and therefore slowing it down. This also has to do with why the IBM PC and IBM PC XT had an 8-bit expansion bus. The 16-bit ISA bus came with the IBM PC AT.

MS-DOS 1.0 used CP/M-80 System Calls to make it easier to port programs from CP/M to DOS. https://www.pcjs.org/documents/books/mspl13/msdos/encycloped...

https://groups.google.com/g/comp.os.cpm/c/hj2M4TIRRKE

https://www.landley.net/history/mirror/ms/InsideDos.htm

https://briancallahan.net/blog/20210606.html

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