[cctalk] Re: 5150 cassette (Was: DLOAD BASIC command for Color Comp

For reference, my notes on the CTR/CCR tape units (and its relationship to CoCo's and the 5150): https://voidstar.blog/all-about-tandy-radio-shack-computer-cassette-recorde… (the Tandy Modem 1 from 1981 also used the cassette port, on one of the TRS-80 systems - at least per its manual) I know IBM had many NDA's when developing the 5150, and also that development was done as secretly and quickly as possible. I don't have any evidence for it, but I always assumed that IBM ended up "borrowing" the tape-cassette interface of the TRS-80, directly because of their relationship with Microsoft. Microsoft released TRSDOS Disk BASIC in 1979 - so they knew how to interface BASIC with disks. TRS-80 Model 3 release date was July 1980 CoCo release date is September 1980 I don't know exactly when the 5150 prototype started (there is an online claim about someone having "the" IBM 5150 prototype board - with a bunch of breadboard yellow wiring like they used on the 5100). There is a date on when IBM contacted Microsoft: July 21st, 1980 (Jack Sams call to Gates) -- same month as the TRS-80 Model 3 release. Then, about a week later: July 27th, 1980 is the date noted when Microsoft bought QDOS. So if Microsoft knew IBM was in a rush, and that IBM wouldn't want to R&D or consider any other new type of cassette-storage system (and there are QIC-based backup systems in early PC Magazine up to even '83 or '84 -- decent capacity, but still expensive as a standalone storage solution) -- Microsoft engineers probably suggested a design they were already familiar with. There was no serial port (on the 5150 mainboard). Maybe they used the tape system to bootstrap early BIOS or MS-DOS revisions? (the disk drive system hadn't been developed yet) OR, maybe use of the tape system was to distract anyone who might ask questions about the system (i.e. keep the system uninteresting). Did IBM also borrow aspects of the 5.25" disk drive system from the TRS-80 Model 3? Maybe not, if the ISA bus required something different for that. But to both Microsoft and IBM, "borrowing" the existing tape system from the TRS-80 seems like a logical decision (cheap, quick, and can test some stuff before the floppy disk solution was finished) - but it's just my speculation. -Steve