krowitz@RICHTER.MIT.EDU (David Krowitz) (08/09/90)
It's my turn to ask for help ...
We just got a Quantum 170MB internal disk for one of our DN2500's.
Of course, it came with cables for a Macintosh, so I'll have to
make my own cables for the DN2500. I think I understand how to
make the SCSI cable ... with the ribbon cable laying flat on the
table, one of the 50-pin connectors should be attached so that the
notches for orienting the connector are up, and the other 50-pin
connector should be attached so that the notches are down. This
gives a cable which attaches the left side of the connector on
the CPU to the left side of the connector on the disk, which is
how the SCSI daisy chaining is done on the Macintosh cable.
From a side view, the Mac SCSI cable looks like this:
+-------+
| |
+-------+.....................................+-------+
| |
+-------+
The power cable is more of a mystery to me, as the Mac power
cable has two different connectors on it, and the drive's
pins on the power cable connector aren't labled. The DN2500's
power cable uses two indentical 4-pin connectors which are
keyed to insure the proper orientation. Two of the possible
configurations are a straight accross or a X-cross. Ie. from
the top view with both connectors oriented with the notches
on top:
+-------+ +-------+
| red |+...................................+| red |
| | | |
| black |+...................................+| black |
| | | |
| white |+...................................+| white |
| | | |
| green |+...................................+| green |
+-------+ +-------+
or
+-------+ +-------+
| red |+..............\ /**************+| green |
| | \ / | |
| black |+==========\ /----------------------+| white |
| | X X | |
| white |+----------/ \======================+| black |
| | / \ | |
| green |+**************/ \..............+| red |
+-------+ +-------+
If you have a working DN2500 with an internal disk, could
you check your cables and tell me whether I'm on the
right track?
-- David Krowitz
krowitz@richter.mit.edu (18.83.0.109)
krowitz%richter.mit.edu@eddie.mit.edu
krowitz%richter.mit.edu@mitvma.bitnet
(in order of decreasing preference)lampi@polari.UUCP (Michael Lampi) (08/10/90)
With respect to the ribbon cable for internal SCSI drives on the 2500, it makes little difference as to which side of the ribbon one crimps the connector as long as you make sure that the marked (normally red) edge of the ribbon is where you place the marked (typically with an arrow or triangular mark or, heaven forbid, with a "1" :-)) end of the connector. This ensures that the cable will be constructed with the proper "keying". With respect to the power connection: the two inner wires are grounds, and the outer wires are +5 and +12 volts. Construct the cable so that the wires are NOT crossed; i.e., pin 1 of connector 1 goes to pin 1 of connector 2, etc.
krowitz@RICHTER.MIT.EDU (David Krowitz) (08/15/90)
Thanks to all those who responded to my question regarding the power and SCSI cables for the DN2500 disks. The quick summary is: For the power cable, the connector's pins are labeled 1-4 (if you look closely, you can see the markings). Pin 1 is connected to pin 1, pin 2 to pin 2, pin 3 to pin 3, and pin 4 to pin 4. This corresponds to the second diagram (the "crossing cable") of my original message. The cable should be about 12" long in order to have a sufficient amount of slack. The SCSI cable is the same as the Mac cable I showed in my original message. With the ribbon cable laying flat on the desk (no folds), one of the connectors should have the key which orients the connector when it is inserted in the drive/CPU on the top side of the cable, and the other connector should have the key on the bottom side. The connectors have a small marking (usually a dot or a triangular mark) on one edge of the connector shell. If the connectors are installed so that both connectors have their orientation marks along the red, or striped, edge of the ribbon cable, then the connectors will automatically be oriented corrected. The cable should be about 16" long to account for the couple of right-angle folds. The Quantum 170S drive formats out to about 165 MB of space. It runs *hot*! I don't have a mounting bracket made up yet, so I've got it lying in the DN2500 with the disk logic board facing up with the DN2500's cover off. The disk is quite hot, but the logic board doesn't seem any warmer than the DN2500's CPU board. The drive seems to be nice a quick. I did a copy-tree from a DSP90 to a DN3500 with a 697MB disk (the Maxtor 8760E disk with the WD7000 controller) and also to the DN2500 with the Quantum 170S. When the directory contained large files (say /lib for example). The Quantum drive was a little faster than the Maxtor 8760. But when the directory contained many small files (/sys/ins for example), the Quantum drive was about 1/3 faster than the DN3500's disk. Deleting the the directories was also faster with the Quantum drive by about 20%. If the heat doesn't turn about to be a problem, this is going to be a nice little system. Thanks again to those who were able to give me a hand. -- David Krowitz krowitz@richter.mit.edu (18.83.0.109) krowitz%richter.mit.edu@eddie.mit.edu krowitz%richter.mit.edu@mitvma.bitnet (in order of decreasing preference)
scott@labtam.oz (Scott Colwell) (08/16/90)
In article <9008141821.AA31711@richter.mit.edu>, krowitz@RICHTER.MIT.EDU (David Krowitz) writes: .. referring to the new Quantum disk connected to the DN2500... > It runs *hot*! I don't have a mounting bracket made up > yet, so I've got it lying in the DN2500 with the disk > logic board facing up with the DN2500's cover off. The > disk is quite hot, but the logic board doesn't seem any > warmer than the DN2500's CPU board. Please check the drive manufacturers specification on allowable mounting orientation. They all (with perhaps the exception of drives for laptops) have only a few allowed orientations and I have never seen them allow the drive to be mounted upside down (i.e. with the logic board up). Putting it up the other way doesn't mean that you will have problems but it may. Also I would be concerned if you formatted the drive this way and even more concerned about the temperature. Drives are more sensitive to temperature than nearly all other components in the machine (tape is bad too), check the temp range in the spec for confirmation. My concern with formatting is that the read/write electronics temp and head position would be quite different when the disk was formatted than when it is properly mounted. This is probably less of a concern than running it upside down for extended periods because I believe the orientation spec is due to the spindle bearings rather than the head forces or temperature. I may be being 'picky' but I do prefer formatting in the final mounting arrangement and I definitely don't run drives upside down for long. (p.s. the sensitive electronics is inside the disk enclosure, not on the logic board.) -- Scott Colwell Labtam Information Systems P/L net: scott@labtam.oz.au Melbourne, Australia phone: +61-3-587-1444
bep@quintro.uucp (Bryan Province) (08/16/90)
In article <5116@labtam.oz> scott@labtam.oz (Scott Colwell) writes: >In article <9008141821.AA31711@richter.mit.edu>, krowitz@RICHTER.MIT.EDU (David Krowitz) writes: >.. referring to the new Quantum disk connected to the DN2500... >> It runs *hot*! I don't have a mounting bracket made up >> yet, so I've got it lying in the DN2500 with the disk >> logic board facing up with the DN2500's cover off. The >> disk is quite hot, but the logic board doesn't seem any >> warmer than the DN2500's CPU board. > >Please check the drive manufacturers specification on allowable mounting >orientation. They all (with perhaps the exception of drives for laptops) >have only a few allowed orientations and I have never seen them allow >the drive to be mounted upside down (i.e. with the logic board up). > >... Also I would be concerned if you formatted the drive this way and >even more concerned about the temperature. > >My concern with formatting is that the read/write electronics temp and >head position would be quite different when the disk was formatted than >when it is properly mounted. This is probably less of a concern than running >it upside down for extended periods because I believe the orientation spec >is due to the spindle bearings rather than the head forces or temperature. > >-- >Scott Colwell >Labtam Information Systems P/L net: scott@labtam.oz.au >Melbourne, Australia phone: +61-3-587-1444 Scott may have a point here. We have been having a similar problem with a Maxtor LTX-200. We didn't have brackets so we placed it upside down on the 2500 in the same way that David did. We did this with two drives both were experiencing problems. One of them we fastened to the side of the drive rack with some screws and then stood the 2500 on its side. The problems stopped! I didn't attach any significance to it until I saw this article. The other drive we left upside down and it continued to have problems and we were just about ready to send it back. I'm going to try mounting it differently and see if that makes a difference. Stay tuned Bat fans! -- --=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-- Bryan Province Glenayre Corp. quintro!bep@lll-winken.llnl.gov Quincy, IL "Surf Kansas, There's no place like home, Dude."
krowitz@RICHTER.MIT.EDU (David Krowitz) (08/17/90)
I turned my Quantum 170S over so that the logic board was underneath and propped it up on a couple of plastic connectors so that it had a 3/8 inch airflow space underneath the drive. It did not get any cooler than before ... on the other hand, I haven't had any problems with the drive operating in either orientation. -- David Krowitz krowitz@richter.mit.edu (18.83.0.109) krowitz%richter.mit.edu@eddie.mit.edu krowitz%richter.mit.edu@mitvma.bitnet (in order of decreasing preference)