AWCTTYPA@UIAMVS.BITNET ("David A. Lyons") (03/03/88)
>Date: Tue, 1 Mar 88 10:39:28 EST >Reply-To: Bruce_Kahn%MAYTAG.CEO.DG.COM@adam.dg.COM >From: Bruce_Kahn%maytag.ceo.dg.com@RELAY.CS.NET >Subject: SCSI / ProDOS Question > > I have been reading a lot about SCSI drives of various sorts and >have heard that up to 8 drives can be put on 1 controller. I would >like to know how, under ProDOS, I would be able to access each drive >if, for instance, they were all 40Megs. Since each drive would be >partitioned into 2 20Megs or 1 32Megs (w 8 for 3.3?), how would the >drives be addressable? Since ProDOS only supplys links for 2 drives >per slot (in the Device Table), would you use some arcane maping >scheme? Bruce True--Apple's SCSI card can handle 8 devices (1 computer + 7 drives, I think). And SmartPort on the IIgs can handle 127 devices (although more than 4 will give you power-supply difficulties). The SCSI card is just like a SmartPort card as far as most software is concerned. Any programs which use SmartPort calls to get at your numerous drives will have no problems. But hardly any programs do, and you wouldn't want them to! (They would be doing BLOCK-LEVEL stuff to your volumes.) So you WANT programs to work through ProDOS, and you want ProDOS to be able to be able to access all your drives. But it can't. All existing versions of ProDOS can only deal with two devices per slot. ProDOS 16 and ProDOS 8 v1.2+ are clever enough to notice if slot 5 contains more than 2 devices, and it will map the 3rd and 4th ones as SLOT 2, drives 1 and 2 [unless you have another disk card in slot 2 already]. I *hope* that future versions of ProDOS 16 [IIgs only, of course] will be able to deal with more devices easily. ProDOS 8 could be improved too, but it would be through more remapping to other slots--the 7-slot, 2 drives per slot idea is firmly built into most ProDOS 8 applications. --David A. Lyons a.k.a. DAL Systems PO Box 287 | North Liberty, IA 52317 BITNET: AWCTTYPA@UIAMVS CompuServe: 72177,3233 GEnie mail: D.LYONS2