rzh@FREEDOM.LLNL.GOV (Roger H. Hanscom (415) 423-0441) (11/15/88)
>Two questions: > (A MEX question) >Part two is more of a hardware question, and does not REALLY belong on >INFO-CPM. I'll ask anyhow: I am comtemplating adding a hard-disk to my system. >There isn't anything on the market (no surprise in the case of a self-built >computer with a non-standard bus). I see two good options: >a. Buy an IBM/PC (8-bit bus, not AT) disk controller, and just adapt the bus >signals (and connectors, of course) to interface it to the Z80 bus. Obviously >I'd have to disable the PC BIOS ROM on the controller card, and I'd have to >find out the low-level commands for the disk controller. Advantage: real cheap. >Disadvantage: No DMA; and it's a kludge; and my machine may get AIDS from the >PC (aargh) hardware. Question: Does anyone have (good or bad) experiences with >using PC periphereals on a Z80 based system? Which controllers are good to use >(for example, well enough documented)? >b. Build my own SCSI controller. As far as I understand SCSI is >just a glorified parallel port and an interface definition. There are >(supposedly) dedicated SCSI controller chips. And one could add DMA (with the >Z80-DMA chip, or with the built-in DMAs in the Z280). Advantage: nice, clean >design. Can be made to be real fast (DMA). Can implement a real nice driver in >the BIOS. Can connect more than just disk drives to the SCSI bus (tape drives >and laser printers come to my mind). Disadvantage: Lots of work. SCSI disk >drives are more expensive. Again, who has experiences with this? Which >SCSI controller chips and disk drives are recommended? >Suggestions (and requests for a summary of all answers) to >Ralph Becker-Szendy RALPH@UHHEPG.PHYS.HAWAII.EDU >University of Hawaii / High Energy Physics Group RALPH@UHHEPG.BITNET >Watanabe Hall #203, 2505 Correa Road, Honolulu, HI 96822 (808)948-7391 No help on Part I here, and Part II DOES belong in INFO-CPM! Look in back issues of MicroCornucopia --- say about March-April or May-June 1987. Dave Hardy devoted one of his last S-100 columns to plans for a wire-wrapped HD interface for the S-100 buss. He used a Western Digital generic con- troller (can't remember the number, but I can get it for you if you want), and the S-100 part was just a bi-directional parallel port to get data and commands to and from the WD card. The WD card can handle up to 2 ST-506 drives (you know, "IBM compatible") that are less costly than SCSI, I think. I was very interested in his design, but the one place that advertised this generic WD controller wants about $180 for it. That's way too high when one can buy a PC controller for way less than half that!! I wrote to him, and asked him about using a PC controller, and hacking it around to work, but he never responded. The generic WD card is *ONE* way to go. There is also a HD kit for the Z80 that apparently uses a little "daughter" board that plugs into the existing Z-80 socket. This comes with the WD generic controller and "software". Definitely the "easy" way to go, but not easy on the wallet -- $500 range. I can get you that address if you're interested. Don't know if it uses DMA. I might be biased here, but I'd avoid dealing with SCSI if I could. Too costly. You can pick up an ST-506 drive (10-20M) for relatively little. See if you can find Dave's article. It'll give you some ideas!! Roger <------------> {ucbvax,ames,lll-crg,....}!lll-lcc!freedom!rzh or {ucbvax,ames,lll-crg,....}!lll-lcc!rzh or rzh%freedom.llnl.gov@lll-lcc.llnl.gov