aptr@uhura.cc.rochester.edu (John Werner) (12/26/88)
NOTE: This article is being cross posted to two newsgroups,
comp.sys.att and comp.sys.ibm.pc because it applies to both groups.
Please edit the Newsgroups lines appropriately. If you wish to make a
comment directly to me, please us e-mail. I read both groups, but not
as much as I would like to. (I recently threw away 2000+ unread
articles in comp.sys.ibm.pc.)
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I have just finished adding a pair of new disk drives to my AT&T 6300
clone. It is actually a Xerox 6064 given to me by my father who works
for Xerox. The drives I added are a 1.2 Meg 5.25" and a 1.44 Meg
3.5". Currently, both of these are sitting on top of topless computer
waiting for a case to arrive from Mead. At this point, everything
seems to run fine, but I have not had a chance to try the 3.5" drive
at 1.44 Meg. I didn't have a chance to get 1.44 Meg disks for it, and
the 720k disks won't format at 1.44 Meg.
The drives are being run off a Compaticard from Micro Solutions. The
Compaticard costs about $175 and is somewhat unique in it ability to
be configured to be any drive contoller. Unlike most drive
contollers, it does not insist on being the primary drive contoller.
This allows it to be used in computers that have built in controllers
(i.e. AT&T 6300). The board also supports just about any type of
drive you could ever want. It even supports 8" disk drives. (Oh, I
do have a pair of 8" drives from a Xerox 16/8 PC that I plan to hook
up soon so I can transfer some long forgotten files from CP/m to
MS-DOS.)
INSTALLATION
Installation of the card is relatively easy and painless if
you do not make the mistakes I did. Jumpers on the Compati Card
select which controller the card will be. In my case, I told it to be
controller 2. You can run up to four controllers on one machine.
Each controller supports 4 drives and has four drive connectors (2
parrallel (sp?) wired pairs), so you can have a total of 16 drives.
There is an edge connector paired with a 34 pin connector, and a 24
pin connector paired with a 37 pin D-connector on the back of the
card. Each pair of connectors is capable of running two drives. For
my system, I chose to use the edge connector.
To connect the drives, you need to have a cable that runs from the
connector on the board to the drives. If you want, you can wire two
drives with one cable, but on one of the drives, 10 to 16 on the
connector must be reversed in order. The twist in the cable is so
that you do not have to change jumpers on the drives. By twisting the
cable, the control lines are reversed so that what used to be the
control lines for drive 2 are now the control lines for drive 1. Most
disk drives are now shipped as drive 2.
Once the drives are set wired up and powered (you will have to give
them power, but if they are in a case this is not too much of a
problem), you can have to install driver software in the Config.sys
file of your boot disk. This software is used to allow DOS to access
the disks. I have no idea what is need to run Xenix or UN*X or
whatever because I have never had to worry about it. The manual does
provide information on how to do low level (DMA) access of the drives.
The manual is is slightly better then the UN*X man pages, but not by
too much.
Once this is all done, you are ready to run. After re-booting the
computer, the drives are ready to test. If you can format a disk on
the drives, then the installation worked. (There is a special format
program provided so that you can use the drives even if your DOS
version does not support the format and/or drive.) After this, they
should run with out any problem.
Now, having described the installation process, I will describe the
mistakes I made on the way.
1) When building the original cable, I somehow managed to do it so
that the connectors where not seated well enough to make contact with
the wires in the ribbon cable. I spent several hours on Christmas Eve
trying to figure out the problem. Eventually, my father and I decided
to rebuild the cables. This solved the problem.
Although the installation manual that comes with it has a trouble
shooting section, we could not find the solution there. On Christmas
Eve, we decided that calling for technical support was not going to
get us very far because no one would willingly be there on a Saturday
to answer technical questions, not to mention this particular
Saturday. The symptoms of the problem were that the drive light would
never come on no matter how we tried to orientate the connector.
2) When we built the cable, we decided not to twist the wires 10 to
16 on one of the connectors and just use the drive select plug on the
1.2 Meg drive to drive 0 from drive 1. The problem with this approach
was that the jumper on the 1.2Meg drive only changed which drive
select line was accessed, not which motor was turned on. Hence,
although we could turn the drive light on, we couldn't do anything
else with the drive. Most of my father's and my experience with disk
drive wiring was with 8" drives in the days of CP/m. On an 8" drive,
the motor is always running, so you never have to wory about toggling
it on or off.
This morning (Christmas morning) it finally occurred to me what the
problem was, and I discovered that the only easy way to get both
drives to work was to use a twisted cable for one.
3) The last problem occurred when I put in the twist in the cable.
Somehow, I once again managed to get a poor connection on the to one
of the connectors and spent some time finding the problem. (Some
problems are just _too_ obvious to consider.)
COMPATIBILTY
So far, every program can access the disks as normal DOS
devices without any problems. I can format, write, and read disks
without any hitches. There are some little inconviences that some
software is giving me.
Both FastBack 2.01 (Fifth Generation Systems) and PC-Backup (Central
Point Software) refuse to try to use physical drives that are above 3.
The two drives I have installed are physical devices 4 and 5, the
lowest possible ones with the CompatiCard being used as controller 2.
This means that I can not use the nice backup features that these
programs provide on my 1.2 Meg drive. (i.e. no formatting while
backing up, no special rercoverable format, etc.) FastBack does allow
the backup to be done to any DOS device, so I was able to run a
backup to the 1.2 Meg drive, but I had to format the disks as normal
DOS disks before doing the backup. This was a bit of pain since I have
60 disks for my backups. (I have 60 Meg of Harddisk on my system.)
The other problem is a very minor. Because of the large size of IBM
PC-DOS 3.3 and my using FansiConsole, EMM drives, and now another set
of drivers for the new drives, I no longer have enough memory to run
one program. If I leave out FansiConsole, I barely have enough memory.
[Aside: FansiConsole now supports the VDC750 in all of its EGA modes,
including 640x400 16 color mode. It even allows you to use 50 line
display in the above mode.]
OTHER NOTES
I have already mentioned that the 6300 has a built in drive
controller. Because the CompatiCard can be configured as any
controller (1-4), it does not have a problem with the 6300s
controller. The thing to note is that the drive configuration
switches on the motherboard should not be changed since they only make
a difference for the built in controller. Changing these caused my
system to lock on boot and return "Bad or Missing Command
Interpretter". (This panicced me a first because there have been some
virus problems on MacIntoshes around here and I thought I might have
gotten hold a PC virus.)
The second note concerns the DMA on the mother board. Other are
several DMA chips that were used. Only some of these are fast enough
to keep up with 1.2 and 1.44 Meg drives. The best way to tell the
difference is to check the number on the DMA. DMAs that will work are
AMD 95117 and NEC 8237AC-5. Other DMAs are probably not fast enough.
There are also two different ways that the chips were mounted. Some
where soldered on and some were socketed. If you have a socketed DMA,
it is a simple matter to change it. (The latest replacement
motherboards to come through the Xerox Service Center locally have had
socketed NEC DMA chips.)
If the DMA is soldered on, you may want someone with experience
working with soldering ICs to help. First off, _do_not_ try to
unsolder the DMA. If something should go wrong and the plating on the
hole is pulled through, you will lose contace to the inner layers of
the circuit board. At this point you will have to replace the mother
board.
The best method for dealing with soldered on DMA chips is to carefully
cut the leads to the chip leaving enough length to solder to. Then
carefully solder the leads of the new DMA to the leads from the old
DMA leads. This can be tricky because the tolerences at this point
are rather small and it is fairly easy to form a solder bridge.
DISCLAIMER: I have never actually tried this proccess, but it has
been recommended by many people I have talked to. I also will not be
liable for any damage you do from either trying this procedure or
having someone else do it. (I really hate to have to put a disclaimer
in, but I can't afford to buy anybody a new computer right now.)
SUMMARY
The CompatiCard from MicroSolutions allows owners of computers
with built in disk controllers to add more disk drives to their
machines. These drives can be on any format and size (3.5", 5.25",
8"). The software comes with drivers for DOS and enough information
to allow custom drivers to be written. Installation of the system is
straight forward, but there may be some machine specific problems
encountered. Overall, it is a very nice and reasonably priced (~$175)
solution to the problem of adding more drives to a 6300.
John Werner
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John E. Werner UUCP: {cmcl2!decvax}!rochester!ur-cc!aptr
aka BITNET: aptrccss@uorvm
The Wumpus Internet: aptr@uhura.cc.rochester.edu
Disclaimer: "Who? When? Me? It was the Booze!" - M. Binkley
--
John E. Werner UUCP: {cmcl2!decvax}!rochester!ur-cc!aptr
aka BITNET: aptrccss@uorvm
The Wumpus Internet: aptr@uhura.cc.rochester.edu
Disclaimer: "Who? When? Me? It was the Booze!" - M. Binkley