OS 9 and earlier only, of course. SCSIProbe won't work in Classic on OS X - because it tries to get too close to the hardware for Classic's liking.
HTH
GWW
On 10 Feb 2004, at 09:30, Gerald Wilson wrote:
It helps if you have the detailed technical spec for the drive, which describes the jumpers and how they're used.
Chances are, for a vintage drive, you won't have this. If you can identify the drive by its manufacturer's cryptic part number, you should be able to find the tech spec somewhere on the web.
You may be lucky and be able to read the part number from the drive label. You can confirm that it is correct if you can get a utility to talk to the drive and show its ROM id and version number. The classic utility was SCSIProbe. Version 3.0 was a reliable version which predates dual-bus Macs. Version 4.3 handles Apple's improved SCSI drivers ("4.3") and understands multiple buses. There's a current version 5.2 from Adaptec, but I haven't used that. If SCSIProbe sees an unterminated bus it will usually flash a warning to that effect. At one time, Newer Technology posted an alpha of a similar utility called "SCSI Info", but I think it never became official.
While early SCSI drives (typically less than1 GB) employed banks of physical termination resistors, later models usually do it all through jumpers. Chances are that there's a jumper marked "TE" which means Termination Enable - ie switch drive termination on. The complication is that there may be another jumper to select "Term Power" - does this drive try to take its termination voltage from its own board, or does it try to take it from a powered line on the SCSI bus?
As a general rule, on a classic Mac SCSI bus, the mobo itself has SCSI id 7, and the main internal drive should be connected at the end of the internal cable, be set to id 0 and be terminated. Any other devices attached between the mobo and drive 0 should be unterminated, and of course have different ids. On a Mac, the SCSI CD is id 3 by convention.
If there are external devices on the same bus, then the bus may need an additional termination, depending on how many devices there are, and how they load the bus. With six or seven devices in total, a second termination is probably essential. With three devices or less, it probably isn't needed (and may interfere with the bus's working). In between, there comes a point where the second termination does more good than harm, so you need to add it.
HTH.
(and all this, btw, is why we now use ATA and FireWire...)
Gerald WW
On 10 Feb 2004, at 01:51, Jack Russell wrote:
On Feb 9, 2004, at 5:27 PM, John Hafemeister wrote:
I'm assuming whatever Mac you are using has SCSI drives, since this the unsupported OS X list? On most SCSI drives there is a jumper setting for termination enabled. Short of looking at the drive and examining the jumper positions, I'm not sure how to determine this? If there is a "remote" way to do this I don't know it.greetings How do I determine if my internal drives are terminated?
HD "termination" is a slightly different animal than termination on an external SCSI chain.
Jack Russell
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