ephraim@think.com (Ephraim Vishniac) (07/23/90)
A few weeks ago, I was complaining to anyone who would listen that the
internal disk in my shiny new IIfx was useless. If any external SCSI
devices were connected, even in a 100% kosher configuration, the
internal drive had intermittent read and write errors. My Apple
dealer was here twice to fix it, without any success. Use of
different terminators, filters, cables, and disks had no effect.
Last Friday, I fixed(?) the problem by accident by adding *another*
external drive and making the external bus longer. The failing
configuration included an Apple CD-SC, with or without a CDC Wren III
disk. Adding another Wren III, for a total of three external devices,
seems to have cleared the problem completely.
When failing, the internal drive would report write errors every
couple of megabytes as I copied files onto it. Attempts to run
"successfully" copied applications from the internal disk usually
ended in disaster. After adding the new external disk, I copied about
60 megabytes of files onto the internal without any problems at all. I
fired up SpInside Mac from the internal and it ran beautifully.
Can somebody explain this please?
--
Ephraim Vishniac ephraim@think.com ThinkingCorp@applelink.apple.com
Thinking Machines Corporation / 245 First Street / Cambridge, MA 02142
One of the flaws in the anarchic bopper society was
the ease with which such crazed rumors could spread.dan@hpnmdla.HP.COM (Dan Pleasant) (07/24/90)
>A few weeks ago, I was complaining to anyone who would listen that the >internal disk in my shiny new IIfx was useless. If any external SCSI >devices were connected, even in a 100% kosher configuration, the >internal drive had intermittent read and write errors. My Apple >dealer was here twice to fix it, without any success. Use of >different terminators, filters, cables, and disks had no effect. > >Last Friday, I fixed(?) the problem by accident by adding *another* >external drive and making the external bus longer. The failing >configuration included an Apple CD-SC, with or without a CDC Wren III >disk. Adding another Wren III, for a total of three external devices, >seems to have cleared the problem completely. > >When failing, the internal drive would report write errors every >couple of megabytes as I copied files onto it. Attempts to run >"successfully" copied applications from the internal disk usually >ended in disaster. After adding the new external disk, I copied about >60 megabytes of files onto the internal without any problems at all. I >fired up SpInside Mac from the internal and it ran beautifully. > >Can somebody explain this please? >-- >Ephraim Vishniac ephraim@think.com ThinkingCorp@applelink.apple.com > Thinking Machines Corporation / 245 First Street / Cambridge, MA 02142 > One of the flaws in the anarchic bopper society was > the ease with which such crazed rumors could spread. ---------- Sure. You obviously displeased the SCSI gods, whose wrath is measured in hours of lost time and lost hair. You apparently found a solution quite by accident, using the time-honored solution of throwing money at the problem. :-) If it makes you feel any better, you're not alone. My IIfx has 4 external SCSI devices, one of which is the Apple CD-ROM device. When the CD-ROM drive was the third external device it would refuse to mount disks. I changed the cables so now it's the first device, and it works. So does everything else (for now!). But I always remember to bow to Cupertino every day at dawn.... Dan Pleasant
dolf@fwi.uva.nl (Dolf Starreveld) (07/24/90)
ephraim@think.com (Ephraim Vishniac) writes: > A few weeks ago, I was complaining to anyone who would listen that the > internal disk in my shiny new IIfx was useless. If any external SCSI > devices were connected, even in a 100% kosher configuration, the > internal drive had intermittent read and write errors. My Apple > dealer was here twice to fix it, without any success. Use of > different terminators, filters, cables, and disks had no effect. > Last Friday, I fixed(?) the problem by accident by adding *another* > external drive and making the external bus longer. The failing > configuration included an Apple CD-SC, with or without a CDC Wren III > disk. Adding another Wren III, for a total of three external devices, > seems to have cleared the problem completely. > When failing, the internal drive would report write errors every > couple of megabytes as I copied files onto it. Attempts to run > "successfully" copied applications from the internal disk usually > ended in disaster. After adding the new external disk, I copied about > 60 megabytes of files onto the internal without any problems at all. I > fired up SpInside Mac from the internal and it ran beautifully. This still sounds like a classic termination problem. Even though termination may be theoretically right, transmission line theory tells you that the so called stub length should not exceed a given length (some ilke 5"). Some disk packaging companies do their internal cabling within the box wrong, making it possible to exceed this limit (without you knowing so) depending on whether you connect an incoming cable to connector 1 or 2. Also, there is a specified minimum distance between two stubs, which again you may have exceeded. This may all sound a bit far fetched, but believe me I have a lot of experience in the SCSI game (I seem to remember you did too. Didn't you write the original Jasmine drivers?) and things like this do happen. The faster hardware gets, the more sensitive it is. I still remember all the tricks I could pull of with a MacPlus, a piece of flat cable with multiple connectors on it to hookk up multiple devices. No longer so! --dolf -- Dolf Starreveld Phone: +31 20 592 5056/5022 (FAX: 5155), TELEX: 10262 HEF NL EMAIL: dolf@fwi.uva.nl (dolf%fwi.uva.nl@hp4nl.nluug.nl) SNAIL: Dept. of Math. and Computing Science, University of Amsterdam, Kruislaan 409, NL-1098 SJ Amsterdam, The Netherlands