neil@uunet.uu.net (Neil Gorsuch) (05/08/89)
In article <258@xermes.UUCP> rob@xermes (Robert A. Schroeder) writes: >I was planning on adding a Maxtor 760 MB SCSI disk to my 4/110. However, >I happened upon some information in the "Hardware READ ME FIRST for the >Sun 4/110 Systems" that floored me. It says: > The Small Computer Systems Interface (SCSI) connector on the Sun > 4100 CPU board installed in your 4/110 system may not adhere > completely to the SCSI specification. Pin 26 on the SCSI connector > may be grounded. Do NOT use non-Sun SCSI disk drives with any Sun > 4/110 or any 4100 CPU based system. Use of a SCSI drive not > purchased from Sun may result in the damage or destruction of the > disk drive/s. Some Sun workstations have the pin that is reserved for supplying termination power GROUNDED. (Amazing how this works out to their advantage :<). That means if you have your disk drive supplying it's 5 volts power to that pin, and if the pin is grounded at the Sun, you will indeed SHORT your disk. All you have to do is look up the termination power source jumpers for the Maxtor and do the following: 1. one of the jumpers will let the appropriate scsi signal (pin 26 sounds right) supply power to the termination resistors location in the Maxtor. DISCONECT THIS JUMPER. That way, whether or not you use the termination resistors in the Maxtor, you won't be shorting anything. Even with the termination resistors removed, both jumpers being left in can still short the disk's 5 volt supply. 2. If you use the termination resistors in the Maxtor, the other jumper will connect the disk drive's 5 volt power supply to the resistors when the jumper is installed. As long as the other jumper is removed, it is safe to install this jumper in any case. You should receive a manual with the drive which will explain these matters in detail (we usually ship manuals with the drives we sell :<). Here is a kludgy diagram, with most of the SCSI signals removed: SCSI TERMINATION JUMPER JUMPER DISK'S POWER PIN------------------o TO o--------------o TO o-------5 VOLT (GROUNDED IN REMOVE | LEAVE SUPPLY SOME SUN'S) | | \ TO ----------------------- / VARIOUS ---------------------- / TERMINATION RESISTOR SCSI PINS --------------------- \ PACKS (LEAVE IN IF THIS \ IS THE LAST SCSI DEVICE) | | | GROUND >Is this for real?? I've given my salesman over a week to try to >confirm/deny this statement and have yet to hear from him. So, I thought >I'd turn to netland for some help on this one. Please tell me it's a >joke (I've actually already ordered the disk :( ). It's no joke, you can short you disk if you don't know what you are doing, and if you assume that Sun ALWAYS provides completely "open systems" compatible equipment. It may possibly have been an honest mistake on Sun's part, but I find it hard to believe that they forgot to check the SCSI interface standard. Neil Gorsuch Uninet Peripherals neil@cpd.com uunet!zardoz!neil (800) 433-6784 outside California (714) 546-1100 inside California