At 10:48 PM +0000 03/19/2003, mark wrote: >I used PC SCSI drives in Macs lots of time without any problems. However I >think there can be a problem with drives that have come out of (I think) >Compaq servers. Something they do to them means they won't always work in >another machine PC or Mac. I think its some sort of low level format.
SCSI is SCSI. It doesn't matter what type of system the drive came from, it will work on your Mac as long as the SCSI versions are compatible. eg: SCSI-2 drive works on a SCSI-1 bus, etc. and you have an appropriate driver. There are (typically) two issues: sector size and jumpers such as spin delay. Before installing ANY hard drive in any computer, you should alway check the jumper settings. In addition to setting the SCSI ID correctly, for a Mac, the drive should be set to spin up on its own! Sometimes, if you have a SCSI chain with a lot of devices, a spin delay is nice (less stress on your overloaded power circuit). But more often than not, it can cause problems. Before using ANY hard drive on any computer, you should reformat it! That long warehouse cook, the freezing UPS truck, the stomping gremlin,... They take their toll. So when you receive any hard drive, give it a day to acclimate to the temperature and humidity conditions, then REFORMAT it. The media's sector size is a low-level format issue, which should be automatically corrected when you reformat. Some formatting utilities, let you set the sector size tho. This is done for performance reasons - big sectors for big files, etc. The Mac OS, by default, likes 512 byte sectors. Note that this is a seperate issue from setting the volume's cluster size - part of a "higher level" format. The cluster size specifies how many sectors will be read or written by the OS at once. >I've >also heard of very old drives that have had the same data on them fore years >can have some sort of a memory effect, where the data can't be erased from >them and thus the drives can't be reformatted. Myth. But#1: older drives do tend to have dying sectors. Reformatting, with a verify pass, will take care of that - maps them out so they're never used again. But#2: simply erasing data (overwriting, usually with all 0 or all 1's) from your hard drive doesn't really make it go away completely. Using special equipment, it is possible to read "layers" of data off the platters, some years old. That's why drives used for classified government work are taken apart and the platters rinsed or dissolved in acid! ...You know the "joke" about the guy that gets into the elevator every day and sees a bag of shredded paper from the floor above? One day he gets in the elevator and there are also two guys from upstairs, quietly chatting about their work - something about reconstructing documents. The next day he gets in the elevator and finds there's a bag of ashes. >With all SCSI drives though, >some like being on certain SCSI ID's better than others. Try them one at a >time until you get one recognised. Some older Macs had difficulty with SCSI ID 5. According to my notes, this was due to a bug which was fixed in SCSI Manager 4.3.1 - which was part of System 7.5.1 (aka System 7.5 Update 1.0), circa 1995. FWIW, - Dan. -- PCI-PowerMacs is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Refurbished Drives | -- Sonnet & PowerLogix Upgrades - start at $169 | & CDRWs on Sale! | Support Low End Mac <http://lowendmac.com/lists/support.html> PCI-PowerMacs list info: <http://lowendmac.com/lists/pci-powermacs.shtml> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive:<http://www.mail-archive.com/pci-powermacs%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
