Talk:Osborne 1

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Besides the tiny display and limited disk capacity, a less obvious Osborne shortcoming was the use of memory-mapped i/o chips. I believe these chips were from the 6502 family that was fully used (with the 6502 CPU) in the Apple II.

Memory-mapped i/o in general and the 6502 family in particular were poorly documented in the CP/M world, so it was much harder for amateurs to write and debug software in assembly language or BASIC for I/O through the Osborne's non-standard chips. Although the competing KayPro is often thought of as a reverse-engineered Osborne clone, in fact the KayPro used I/O chips from the Zilog-80 family that used conventional I/O addressing. These chips were well-documented and much easier to program without a Ph.D. in electrical engineering.

Yet another Osborne shortcoming was that serial i/o only worked reliably up to 1200 baud (bits per second). In an office setting where 5-1/4" and 8" floppy disks coexisted and LANs were still years off, file transfers via serial ports were often necessary to move files between computers with incompatible disk formats. At 1200 baud, moving the mere 90K bytes of a full Osborne single-sided/single density floppy disk to a computer with 8" floppies took 12.5 minutes, plus overhead for disk reads and writes. KayPros and other CP/M computers with Zilog chips could run their serial ports at at 19,200 baud, 16x faster! DaveM, Los Angeles