[cctalk] Re: First non-IBM PC-DOS Compatible PC

Chuck: Thanks but AFAICT the Columbia MPC-1600 was not PC-DOS compatible MS-DOS and PC-DOS Because PC-DOS and MS-DOS share the same origins, the quest for a compatible operating system isn’t formidable. To successfully emulate PC-DOS, we at Columbia Data Products (CDP) provided a second BIOS and modified the MS-DOS source code. MS-DOS requires its own BIOS to provide a well-defined interface between the operating system and the hardware and peripherals. On the PC or a compatible, however, the PC MS-DOS BIOS uses the ROM BIOS and its existing low-level drivers. Therefore, the machine independent part of MS-DOS resides in RAM with the tailored MS-DOS BIOS. The resulting operating system behaves like PC-DOS. Because the same level of documentation is not made available for the PC-DOS BIOS Technical Aspects of IBM PC Compatibility Byte November 1983 This article was written by staffers at Columbia Data Products Inc. https://archive.org/stream/byte-magazine-1983-11/1983_11_BYTE_08-11_Inside_… Apparently Columbia like Compaq did independently develop their BIOS but with the objective of MS-DOS compatibility and a I think a proprietary version thereof. And the article referenced says they both did a very good job This is also confirmed at History - Who were the first engineers to <https://retrocomputing.stackexchange.com/questions/5855/who-were-the-first-engineers-to-cleanroom-the-ibm-pc-bios> "cleanroom" the IBM PC BIOS? - Retrocomputing Stack Exchange I seem to recall the critical tests were some games that made extensive use of the IBM PC video BIOS calls. Still looks like Phoenix or Tandon as the first with a PC-DOS compatible BIOS Tom -----Original Message----- From: Chuck Guzis &lt;cclist(a)sydex.com&gt; Sent: Monday, June 05, 2023 11:03 PM To: Tom Gardner via cctalk &lt;cctalk(a)classiccmp.org&gt; Subject: [cctalk] Re: First non-IBM PC-DOS Compatible PC On 6/5/23 22:28, Tom Gardner via cctalk wrote: That's a tricky one,I think. For example, if a single programmer read the IBM PC BIOS listing (or even disassembled it) and then wrote a new one from scratch, that derivative BIOS in the view of the IBM legal beagles would not have been legal. If, on the other hand, the same programmer never saw any of the code, but read the API description and wrote a BIOS, that would be legal. Both ERSO and Phoenix resorted to a "clean room" method where one team read the PC BIOS and wrote a description, which served as a specification for a derivative BIOS. I think that the descriptions were cleaned up a bit and published as the Phoenix BIOS books. But I think the first "clean room BIOS" was in the Columbia MPC-1600, June 1982. --Chuck