Ask Howard: Would it have been possible to run MS-DOS on the ADAM?


I’m not as brainy as a lot of the Coleco ADAM users, so sometimes I ask questions that may seem obvious to them.  However, asking these obvious questions to the right person sometimes reveals interesting tidbits of history I knew nothing about.  So I asked Howard Eglowstein, a Senior Software Engineer at Coleco, if it would have been possible to run MS-DOS on the ADAM.  Howard writes:

“On the face of it, no. MS-DOS was written as 86-DOS and then Microsoft bought it.  From conception it was written for the 8086 processor (but designed to feel like CP/M) and never existed for a Z80 or 8080.  ADAM seriously failed a requirements test because it was the wrong chip.”

“That said, there was a proposal floated around that would have changed that.  The IBM-PC Jr was a lightweight PC for the home.  To make sure that it didn’t dominate the space, Steve Perlman (who later went to Apple, then came up with WebTV and OnLive) had proposed a box that sat on the side of the ADAM and had an 8088 processor.  The ADAM served as a platform to emulate the peripherals that a PC clone needed.  So when the chip wanted to talk to a disk, it talked to the Z80 and said “pretend you’re a disk and get me a boot sector”.  The Z80 then talked to the ADAMNet master, etc. and did what it could.  If you decided that was too slow (and it would have been awful) you could buy addons with real PC hardware in them.  In particular the memory emulation alone would have made the scheme unworkable.  Steve certainly thought outside the box though, and had that gone forward we would have turned ADAM into the world’s slowest PC compatible.  I have the original spec here somewhere. I should find and post it. It’s beautifully written and quite clever.”

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