<SNIP> The single internal drive plugs into the hard-sectored controller board. There should be a short ribbon cable from the drive to the board. The external drives should plug into a socket on the rear apron of the machine (unless they didn't install the plug; then you'll have to route the cable directly to the double-density controller board). I own an '89 myself, and they're pretty similar. It's been so long, I'm straining my synapses to remember the keypress to boot off of the external floppies. There is one keystroke that will cause the thing to boot from the internal drive. Make sure the fan blows really good, these suckers tend to overheat (I knew a guy who ran it with the cover off, with a *BIG* muffin fan pointed at the PSU). They also prefer filtered power-- we used to screw up alot of floppies before we got a SOLA . . . . Funny, you know last nite I was seriously thinking about resurrecting the 'ol H-89, now that I have the space to do so. . . . I dunno about this display board. There were a few graphix cards built for these. I have some old magazines that may yield a clue . . I may be able to help with the FDC print, assuming it's H/Z standard issue (that's what I have). There were at least two other third-party DS/DD FDC's for it. Zenith docs are good, but configuring CP/M to work with the external 80-track drives can be a royal pain, unless Zenith was nice enough to supply a pre-configured floppy (mine was a Heathkit, so we had to do everything from scratch). Unfortunately, I know almost nothing about H-DOS, but I think I have some software for it hanging around here someplace. . . . Jeff

At 19:23 05-05-98 +0100, ard(a)p850ug1.demon.co.uk (Tony Duell) wrote: I've had experience with most of the Heath/Zenith 8-bit machines. I have an H-8 and an H-89 (which actually is the good ole Heathkit version of your Z90). The Z90 was a Zenith Data Systems-branded machine which is Heath factory-built. It had a bit different setup than the factory-built or kit versions bought from Heath (the H-89). Don't quite know what those differences were though, but the H-89 and Z-90 were still very similar. Still have the equipment, most all docs, H-8 and H/Z-89-related magazines, etc. but memory fading from lack of use of it the past five or seven years :( Same goes for my H/Z-100 and H-8 machines. The H/Z-100, incidentally, could be considered Heath/Zenith's answer to the transition from a CP/M world to the then-new Messy-DOS world. Had an 8-bit 8085 running CP/M-85 and a 5 MHz 8088 running M$DOS version 1.25. Expansion bus containing floppy/hard disk and video cards is S100. Was well-respected and somewhat revolutionary for its time. Kinda pricey when new. US military bought several thousand. Mine has the later third-party IBM PC compatible conversion boards and 30 meg HDD and 768K RAM modification. H/Z-89/90 enclosure actually is the H/Z-19 terminal Heath designed in '79 or so to replace the H-9. Does actually fully emulate the VT52 when put in that mode. You can disconnect the serial cable to the Z90 Mainboard and use it as an H/Z-19 or VT52 if you need a terminal in an emergency. Are the floppy drive cables disconnected Tony? Vaguely recall a 3rd party graphics board. Can you see a name, etc. on it?? I may be able to lookup an old advertisement or something for you on it. I think I could help you on this if I can find my library of H/Z-89 docs. We just moved into a new house you know, so I have to determine just which box it is! Love the VERY thorough manuals Heath Corp wrote. Generally agreed amongst the electronic collecting community that there is nothing like them from anybody else. So, up until the early 90's or so, when Groupe Bull bought Zenith Data Systems, Zenith's manuals and some hardware features on their computers had been top-notch as a result of Heath's engineering. Not so after Bull took over. I think it was sort of based on RT11. Somebody either here or on the Heath list mentioned that. You see, around the time the 8080-based H-8 was introduced, Heath had already (or just about to) released the H11 which is an LSI-11 based machine. It used a DEC CPU board and a modified RT11 OS called HT11 which was distributed on paper tape. Later just RT11 itself IIRC was distributed. RX01 drives came along too. I haven't used HDOS (the Heath-written OS for the H-8) much at all but I *think* some of the functions look like RT11 too. Gotta check that more. I've got a couple of H11 systems which I need to restore. Need a decent DEC OS on RX01's first as they came with no disks :( (Suggestions anybody?) I can help some Tony, and I think there's others here who have some Heath/Zenith 8-bitters. Send a private email if you want to discuss any details (unless if of course you feel the group would be interested, then post here). Have fun with it, Chris -- -- ======================================================= Christian R. Fandt, Electronic/Electrical Historian 31 Houston Avenue, WE Phone: +716-488-1722 -Home Jamestown, New York +716-661-1832 -Office 14701-2627 USA Fax: +716-661-1888 -Office fax email: cfandt(a)servtech.com Member of Antique Wireless Association URL: http://www.ggw.org/freenet/a/awa/