djo7613@blake.acs.washington.edu (Dick O'Connor) (06/30/89)
Apparently a consultant who used to work here left one of our divisions
with a hard disk he promised to add to an AT with an existing HD. Details
are scanty, cables seem to be missing, and I have a couple of questions
maybe some of you HW types can answer why I scramble to make something
of this mess.
I'm familiar with my own setup: one hard disk, one controller board, two
cables (one wide, one narrow, one called "data", other called "signal" I
*think*). The controller in the AT right now is the same as mine: an
RLL board driving a Seagate ST238R, 30MB, 65ms. The hard drive they want
to add is a Micropolis model of uncertain lineage (I can take another look
for a model number). The new controller apparently can handle two drives
(two narrow connectors, one wide; why is that all that's needed, BTW?), but
I can't find any identifying marks on it and I wouldn't know an MFM board
from an RLL board if it bit me in the foot.
If we discover that it's an RLL board, can we run two drives off it in an
AT even if the drives themselves have differing rated access times? If it's
an MFM board, can two such boards (MFM and RLL) coexist in the same AT
(actually clone I should say) and drive two different HD's? That doesn't
sound possible. And finally, could we low-level reformat the Seagate with
the new controller (if it's MFM), take the drop to 20 MB, and run the
two drives?
Gee, just when you think you start to know something about this wacky
business, someone comes up with something *new*!
P.S. We can't find any cables with the new drive (sigh). What's needed to
make things work here, another narrow cable? Are identical cables used
for MFM and RLL and ??? hard disks?
"Moby" Dick O'Connor
Washington Department of Fisheries
Olympia, Washington 98504
Internet Mail: djo7613@blake.acs.washington.edu
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DISCLAIMER: I speak only for myself, not for the Department. Here, anyway!
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So long, and thanks *from* all the fish...marc@rna.UUCP (Marc Johnson) (07/04/89)
In article <2609@blake.acs.washington.edu> djo7613@blake.acs.washington.edu (Dick O'Connor) writes: > >Apparently a consultant who used to work here left one of our divisions >with a hard disk he promised to add to an AT with an existing HD. Details >are scanty, cables seem to be missing, and I have a couple of questions >maybe some of you HW types can answer why I scramble to make something >of this mess. > While I'm not a hardware maven exactly, I have added drives to machines, so I think I can help a little. >I'm familiar with my own setup: one hard disk, one controller board, two >cables (one wide, one narrow, one called "data", other called "signal" I >*think*). The controller in the AT right now is the same as mine: an >RLL board driving a Seagate ST238R, 30MB, 65ms. The hard drive they want >to add is a Micropolis model of uncertain lineage (I can take another look >for a model number). The new controller apparently can handle two drives >(two narrow connectors, one wide; why is that all that's needed, BTW?), but >I can't find any identifying marks on it and I wouldn't know an MFM board >from an RLL board if it bit me in the foot. > >If we discover that it's an RLL board, can we run two drives off it in an >AT even if the drives themselves have differing rated access times? If it's >an MFM board, can two such boards (MFM and RLL) coexist in the same AT >(actually clone I should say) and drive two different HD's? That doesn't >sound possible. And finally, could we low-level reformat the Seagate with >the new controller (if it's MFM), take the drop to 20 MB, and run the >two drives? > Okay, here's the story: RLL is just another method of encoding the information on the disk. It packs significantly (40%-ish) more data in the same space as MFM. Example: Adaptec's 4000A board (MFM) writes 17 512-byte sectors per track, while their 4070 board (RLL) writes 25 512-byte sectors per track. The access time has little to do with it. The quality of the disk media determines whether you can jam RLL-dense data on or not. Lower quality drives (cheaper) can't handle it. Better quality drives (Priam, for example), WHETHER OR NOT THEY ARE RLL RATED, will handle RLL-density data. The "R" suffix on the Seagate just means they rated it for RLL-density. I don't have a feel for the quality of Micropolis drives, but you can try it and if you don't get a lot of bad blocks when you format, you're in business. It's kind of like using a DS-DD floppy at HD format. I'm not sure know if you can run two different controllers in the same machine, not having done it, but I suspect you can, as long as the drives are properly jumpered. The computer doesn't care about disk density--that's the controller's problem. You can certainly reformat your RLL-rated Seagate at MFM levels if you want. As far as cables go, you will need a 2nd "narrow" (data) cable going from the unused 20-pin socket on the board to the 20-pin edge connector on the 2nd drive (drive 1). Such cables are readily available from computer supply places (try Altex Electronics 800-531-5369). Examine your control (34-pin) cable: it should have 5 wires twisted near the end connector, and a 2nd connector near the middle of the cable. If not, get a cable fitting this description. The end with the twists goes to the first drive (drive 0), the middle connector to the 2nd drive (drive 1), and the other end to the controller. Be sure that the red stripe along one edge of the cable goes to pin 1 on each end. Now check the jumpers on the drives. Due to the twisted cable (don't ask...) both drives must be jumpered as drive 1. Seagate calls this "DS2", while Miniscribe and Priam call it "DS1". I don't know what Micropolis calls it, but it's the SECOND setting on the drive select jumpers. Remove the resistor termination pack from the 2nd drive (drive 1) ONLY. This is a set of resistors in a unit, near the cable connections on the board side of the drive, usually inserted into a socket with 8 or 10 round holes for the pins. If the pack is not removable on one of the drives, swap 'em. The last drive (drive 1), which you connect to the middle of the 34-pin cable, is the one to remove the termination pack from. Got all that???? >Gee, just when you think you start to know something about this wacky >business, someone comes up with something *new*! > >P.S. We can't find any cables with the new drive (sigh). What's needed to >make things work here, another narrow cable? Are identical cables used >for MFM and RLL and ??? hard disks? > Again, you'll have to get a 2nd 20-pin cable, and possibly the proper 34-pin cable with the 5 twisted wires. The cable types are the same for MFM and RLL and all drives. >"Moby" Dick O'Connor >Washington Department of Fisheries >Olympia, Washington 98504 >Internet Mail: djo7613@blake.acs.washington.edu Good luck. marc =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= = Marc Johnson BITNET: rna!marc@rockvax.bitnet = = Rockefeller Univ. Neurobiology UUCP: ...cmcl2!rna!marc = = New York City INTERNET: marc%rna@rocky2.rockefeller.edu = = (129.85.2.1) = = = = "Gimme the beat boys and free my soul, I wanna get lost in your rock & roll = = ...and drift away" = =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=