ba@m-net.UUCP (Bill Allen) (11/21/88)
Does anyone know how one such computer shop in TX can offer
complete hard drives, the SCSI host controller, the case,
the power supply, and the hard disk with prices like:
A500/1000 A2000
20meg $639 $539
40meg $799 $749
65meg $879 $799
This is 50% less than any other drives I've seen offered.
--
---------------------------------------------------------
Reply-To: ba@m-net.UUCP (Bill Allen Beogelein)
Organization: M-NET, Ann Arbor, MI
---------------------------------------------------------michael@nacom.NACNET (Michael Hullhorst) (11/22/88)
When it came time to outfit my A2k with additional byteage I looked around, mostly with Computer Shopper, and found an outfit out of Arizona called Hard Drives International in Tempe AZ 1-800-234-disk. They sold me a ST277N (SCSI) 64M drive for $489.00 ( this was 03/18/88 ). You can get a SCSI controller from C-Ltd for about $180, that and a little work you can outfit your A2000 with some serious disk. The price for A1000s will of course be higher because of the additional equipment (ie power supply, case, ect).
scott@applix.UUCP (Scott Evernden) (11/22/88)
In article <2570@m2-net.UUCP> ba@m-net.UUCP (Bill Allen) writes: >Does anyone know how one such computer shop in TX can offer >complete hard drives, the SCSI host controller, the case, >the power supply, and the hard disk with prices like: > A500/1000 A2000 > 20meg $639 $539 > 40meg $799 $749 > 65meg $879 $799 >This is 50% less than any other drives I've seen offered. These prices are not particularly low. You can do better by shopping around and building yourself. For example, to add a HD to my A1000 cost me (approximate prices): $440 Seagate ST277N (65meg SCSI) $115 Case and p.s. (I splurged on this) $95 SCSI controller (StarDrive) $20 2 Cables (Some handiwork required) ? Amiga Boing nameplate which is over $200 less than the price you posted. I always study Computer Shopper mag to learn about prices.. -scott
pdg@hpcupt1.HP.COM (Paul Gootherts) (11/23/88)
> $20 2 Cables (Some handiwork required)
Please elaborate. I need to get/make a cable to go from the back of an
ST-225N (50 pin ribbon) to either a 50 pin SCSI connector or a 25 pin
MAC connector.
What kind of cable do you run from your drive to your controller? If
you built it from scratch, how did you find out what the pin connections
are?
- Paul Gootherts, Hewlett-Packard Co, hplabs!hpda!pdgthad@cup.portal.com (Thad P Floryan) (11/24/88)
Re: SCSI cabling and wiring, the following contains some stuff I posted to
{comp.periphs, comp.sys.att, unix-pc.general} earlier this year.
This information was also reviewed by John Lohmeyer (Chairman of the ANSI
X3T9.2 SCSI Committee) who commented favorably on the diagrams; he also has
flamed Apple for their controversion of the SCSI specs (both in private
correspondence with me and publicly in a recent article in MAC WEEK).
In any event, here's the material; enjoy!
Thad Floryan [ thad@cup.portal.com (OR) ..!sun!portal!cup.portal.com!thad ]
======================================== BEGIN EXCERPTED MATERIAL:
Many systems supporting SCSI (Amiga, Mac, etc.) use a DB25 connector at
the host-adapter end to save real-estate; the SCSI devices themselves
use the "correct" 50-pin connectors (either Centronics 50-pin or the
dual-25 row kind).
The so-called "Mac System Cable" has a DB-25 on one end and a Centronics
50-pin connector on the other. SCSI interconnects are 50-wire.
At the end of this posting are the pinouts of the DB25 and the 50-wire.
One thing I've noticed (after adding over 1GB HD and a Fujitsu 190MB tape
drive to my Amiga's SCSI bus) is that some device manufacturers take liberties
with SCSI wires 20,22,24,28,30, and 34; some tie these to ground, some tie
them to +5VDC, and some leave them (properly) unconnected.
Another caveat with multiple devices on a given bus is to be SURE that only
one is supplying +5VDC on SCSI pin 26 for terminator power. Some mfrs provide
jumpers to enable/disable, some feed thru a diode, some feed the power out
"raw", and some do nothing.
What I do on my system is supply terminator power from the host adapter, and
use an external terminator at the END of the bus.
From my experience, what I suggest is that when you're making the cabling,
pull pins 20,22,24,26,28,30,34 from the connector that attaches to the embedded
SCSI drive and/or SCSI translator. I've noticed that Apple's SCSI interconnect
cables do NOT pass pins 20,22,24,28,30,34 (for the reason I noted above).
Another observation I'd like to make is that MANY of the 3rd party consumer-
grade mfrs of SCSI HDs wire their boxes INCORRECTLY. SCSI specs mandate no
more than a 10cm "stub" off the bus, yet many Mac-type drives I've opened up
(just gotta see what's in there! :-) have a 2" 50-wire connection joining the
two Centronics connectors continuing with a 15" stub to the 50-wire connector
on either an embedded SCSI drive or an Adapter 4000A or 4070 translator. This
mis-wiring would account for the problems people have running a SCSI bus out
to 20 feet (I have no problems since I wired my systems correctly, and the
last device is 19' from the host adapter). Remember: SCSI wiring is
supposed to be DAISY-CHAINED, per:
WRONG: CORRECT:
____________________ __________________
/ \ / \
[] | [] |
\ \_DISK \_DISK
/ /
[] [] |
\__________________/
The "[]" is a 50-pin Centronics connector
SCSI Connector (DB-25)
Pin Name
-------------
1 REQ
2 MSG
3 I/O
4 RST
5 ACK
6 BSY
7 GND
8 DB0
9 GND
10 DB3
11 DB5
12 DB6
13 DB7
14 GND
15 C/D
16 GND
17 ATN
18 GND
19 SEL
20 DBP
21 DB1
22 DB2
23 DB4
24 GND
25 N.C. (or) Terminator Power
SCSI Connector (50 pin header)
Pin Name Pin Name
-----------------------------------
1 GND 2 DB0
3 GND 4 DB1
5 GND 6 DB2
7 GND 8 DB3
9 GND 10 DB4
11 GND 12 DB5
13 GND 14 DB6
15 GND 16 DB7
17 GND 18 DBP
19 GND 20 GND <- caution: not always
21 GND 22 GND <- caution: not always
23 GND 24 GND <- caution: not always
25 N.C. 26 Terminator Power
27 GND 28 GND <- caution: not always
29 GND 30 GND <- caution: not always
31 GND 32 ATN
33 GND 34 GND <- caution: not always
35 GND 36 BSY
37 GND 38 ACK
39 GND 40 RST
41 GND 42 MSG
43 GND 44 SEL
45 GND 46 C/D
47 GND 48 REQ
49 GND 50 I/O
==================================================
SCSI PERIPHERAL BOX INCORRECTLY WIRED (LONG STUB):
+------------------------------+
| _________ |
|_/ ^ \ |
to/from bus -[_] | \ |
| \ | \__[== periph. |
|_/ | |
to/from bus -[_] | |
| stub |
| |
+------------------------------+
SCSI PERIPHERAL BOX CORRECTLY WIRED (DAISY-CHAINED, SHORT STUB):
+------------------------------+
| ___________ |
|_/ \ |
to/from bus -[_] \ |
| \[== periph. |
|_ / ^ |
to/from bus -[_] / | |
| \___________/ stub |
| |
+------------------------------+
_
Each [_] is an IDC Centronics 50-pin connector
Each [== is an IDC dual-25 row connector
Note: ``IDC'' means Insulation Displacement Connector, the type whose parts
are squeezed onto ribbon cable.
==================================================
Final note: you'll save yourself a lot of time (and possibly grief) by
simply buying a so-called "Mac System Cable" (50-pin Centronics to 25-pin
DB25); the brand I use is Data-Spec (just as good and much less expensive
than the stuff from Apple and other 3rd party mfrs).
Thad Floryan [thad@cup.portal.com (or) ..!sun!portal!cup.portal.com!thad]ltf@killer.DALLAS.TX.US (Lance Franklin) (11/26/88)
In article <11728@cup.portal.com> thad@cup.portal.com (Thad P Floryan) writes: >Final note: you'll save yourself a lot of time (and possibly grief) by >simply buying a so-called "Mac System Cable" (50-pin Centronics to 25-pin >DB25); the brand I use is Data-Spec (just as good and much less expensive >than the stuff from Apple and other 3rd party mfrs). I agree...I got mine from Connections Unlimited, Inc., here in Dallas. Cost me $14.95, I think...check the Computer Shopper for their address and phone number. I had to connect a Microbotics StarDrive interface (with a 25-pin connector) to an Adaptec 4070 SCSI interface (with a 50-pin header). I bought one of these 25-to-50 pin MAC-SCSI cables, then went out and bought a 50-pin flat-cable-type header, a Centronics-type connector that works with flat cable and some 50-wire flat cable...made up a cable with the 50-pin header on one side and the 50-pin centronics-type connector on the other. The 50-pin header plugged into the Adaptec, I mounted the 50-pin centronics connector to the back of the HD case, plugged the 50-pin end of the MAC-SCSI cable into it, and the 25-pin end into the Microbotics interface...works perfectly, and cost me about 30 bucks for the whole cable setup. Lance -- +-------------------------+ +-----------------------------------------------+ | Lance T Franklin | | I never said that! It must be some kind of a | | ltf@killer.DALLAS.TX.US | | forgery...I gotta change that password again. | +-------------------------+ +-----------------------------------------------+
cmcmanis%pepper@Sun.COM (Chuck McManis) (11/30/88)
In article <6080009@hpcupt1.HP.COM> (Paul Gootherts) writes: >> $20 2 Cables (Some handiwork required) > >Please elaborate. I need to get/make a cable to go from the back of an >ST-225N (50 pin ribbon) to either a 50 pin SCSI connector or a 25 pin >MAC connector. > >What kind of cable do you run from your drive to your controller? If >you built it from scratch, how did you find out what the pin connections >are? >- Paul Gootherts, Hewlett-Packard Co, hplabs!hpda!pdg Building a SCSI cable is fairly straight forward, yet it requires some manual dexterity and a good vice (smoking won't do :-)). The connector on the back of nearly every SCSI *device* known to man is a 50 pin parallel connector (2 rows of 25 pins) with a .1" pin spacing. The device will have a male plug the cable will require a female socket. An "insulation displacement" version of this connector will cost about $6 list at Active electronics or an equivalent. The "external" connector is specified by the SCSI standard to be a 50 pin "centronics type" connector. These are both a bit more expensive and a bit tougher to find. The local sales office of AMP sent me one as a sample, you may have to go through Hamilton-Avnet or an equivalent electronics distributor to get one. The single piece price of these varies, I was quoted $10. Since there is often a minimum purchase from a distributor you may end up buying more than one. (Arrow has a minimum purchase of $25, the salesperson offered to put one, two or three connectors in the box :-)) This connector will be a female I believe, since I don't have a Mac cable handy I'm guessing. The final piece of the mystery is some 50 conductor flat cable. This stuff is usually gray with a red stripe along one side of it. It will cost between $.50 and $1.50 a foot depending on your supplier, often, from a surplus store, you can buy a "scrap" cable that uses 50 conductor ribbon cable, cut the ends off and use the resulting length of cable in your new cable. If you use this method you should check for "missing" conductors or damage to the ribbon cable. Now you have your three pieces, two connectors and a section of ribbon cable. Carefully disassemble the 50 pin parallel connector and insert the cable between the "back" and the sharp "spines" on the connector. Note that the connector has an arrow or dot or the number 1 on the side where the red stripe should go. Let some of the cable pass through so that you have about 1/2" of cable on one side of the connector and the rest on the other side. Now place the whole deal into the vice so that closing the vice will squeeze the cable between the spines and the "back". MAKE SURE that the cable is perpindicular to the connector and that the spines all line up with conductors in the cable. Then, while keeping the various parts in place, clamp the vice down on the connector. It will "give" slightly when the spines displace the insulation, and the back of the connector will "snap" into a holding position. When there is no gap between the connector pieces and the cable give the vice an additional quarter turn and count to ten. This will insure the connection. Now remove the whole assembly and you will have something that from the side looks like this : XXX <- Connector back ------------------------XXX----- <- Excess Ribbon cable XXX <-- Connector front. XXX Using a pair of sharp scissors or an exacto knife cut off the excess cable, fold the remaining cable over the back and attach the strain relief. Do the exact same thing for the other connector on the other end. Now you can connect this cable to your disk drive or what ever inside the case and leave the 50 pin "centronics" type connector outside of the case. If you need to go from this connector to a 25 pin Mac type connector then by a Macintosh SCSI cable (off the shelf at about $19.95) if you need to go from this connector to another 50 pin centronics connector you can get a Macintosh SCSI "extension" cable off the shelf and use it. I don't reccomend you build your own 25 pin -> 50 pin cable. Good luck, --Chuck McManis uucp: {anywhere}!sun!cmcmanis BIX: cmcmanis ARPAnet: cmcmanis@sun.com These opinions are my own and no one elses, but you knew that didn't you.
nschultz@polyslo.CalPoly.EDU (Ned W. Schultz) (01/28/89)
The 256x4, 100 ns chips are part # MB81C4256-10.
From Advance Micro Technology in Santa Clara. (408) 496-1122
$29-31, depending on the day you call!
Ned Schultz nschultz@polyslo.calpoly.edu
polyslo!nschultz