DOS code in CP/M? Revisited...

Fred Cisin cisin at
Thu Jul 14 12:21:28 CDT 2016

>> When IBM decided to take over the personal computer market, they didn't do their homework very well.
>> Intel convinced them to use the 8088, to have a gateway into 16 bit, instead of building a true 8 bit machine.
>> One of the IBM people had seen a "Microsoft Softcard" (a Z80 co-processor plus CP/M for Apple][).

On Thu, 14 Jul 2016, Guy Sotomayor Jr wrote:
> IBM chose the 8088 because the bus was close enough to the 8085 that the 
> peripherals from the S/23 could be re-used with minor tweaks (in many 
> cases just a re-layout).
> They wanted something that would allow > 64KB of RAM without having to 
> go through the pains of what was done on S/23 (it was an 8085 system 
> that has 192KB of ROM and upto 128KB of RAM) and none of the 8-bit 
> micros could do that.

It makes sense to me.  Hardware would be same as for an ordinary 8 bit 
machine, but lots more (1MB!!) memory map.
Since nobody could possibly need more than 10 times the current RAM, big 
chunks of space could be used for memory mapped I/O, such as both a text 
display AND an amazing 640x200 graphics display.

> IBM had looked at the PC market for a while.  It was actually TJ Watson 
> Jr that instructed that a “skunk” team be formed to see how quickly 
> a PC with an IBM logo could be produced.  He was afraid of Apple making 
> inroads into IBM’s traditional markets and wanted to prevent that. 
> It was never envisioned to be a huge market for these things…it was 
> viewed only as a hobbyist thing that had the potential to take away 
> business from IBM’s traditional machines.

They assumed [correctly] that they could, with trivial ease, simply step 
in and dominate that "home computer" market.  Particularly useful if 
anybody was crazy enough to take in a home computer to work and use it 
for some minor office tasks.

I'm glad that Apple survived IBM's entry and presence in that market.

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