scott@CIE.UOREGON.EDU (10/08/89)
Here's a summary of what many have written me and what I've
learned from it.
MAKING HARD DRIVES EASY
(for the Atari ST)
The Atari is a wonderful computer with a DMA port on the rear
that holds the promise for incredible data transfer speeds. While
IBM PCs must clunk along using their 4 MHz CPUs to handle the data
transfer, the Atari's DMA has direct access to memory and is not
hampered by CPU speed. This means that we Atari owners can really
take advantage of the speed hard drives offer.
There are some companies making hard drives just for the Atari,
but unfortunately the prices are high and the options few. This is
what I shall try to remedy here by telling you what I've learned
about putting together your own hard drive to meet your needs
affordably. A few days ago, I knew nothing about hard drives. Now I
feel comfortable about putting together my own. That is how easy it
is to learn. (disclaimer: I don't mean that it is easy to actually
put together; I haven't done that yet. It's easy to learn _what_
to put together.)
There are three basic components to consider when making your
hard drive: the hard disk mechanism, the hard disk controller, and
the host adapter. I'll discuss these three first and then go on to
talk about the extras, e.g. case, power supply, fan, and cables.
HARD DISK MECHANISM: This is the heart of your hard drive. It
consists of platters covered by a magnetic media sealed in a metal
case with various muck a muck electronic stuff. There are basically
two standards to consider: MFM (Modified Frequency Modulation) and
RLL (Run Length Limited). MFM is an older standard of formatting that
allows for 17 sectors per track and RLL is a newer standard that
allows for 26. (RLL is also faster because of this) RLL requires
better quality disks than MFM, so when a disk is labeled as MFM or
RLL, that just tells you the quality of the magnetic media on the
disks. (There are other standards such as ESDIC, but they are not as
important for us.) Another measure applied to disk mechanisms (besides
their capacity) is their seek speed. Usually measured in milliseconds,
ms, this is the time it takes for the heads to move to a new track and
settle-- the lower the number, the faster the drive.
Two companies were recommended to me more than any others:
Seagate and Miniscribe. Seagate is my choice though because it is
well known and common. Some complaints about the two were that the
Minscribes are very noisy and prone to break down, and that the
Seagates are very hot when they operate. (be sure to get a fan.) A
note of warning here: some hard disk mechanisms come with an
"embedded" disk controller, notably the Seagate series with the "N"
suffix, and many of these embedded controllers are buggy. (The
Seagate "N" series have/had a bug where they won't accept commands
just after finishing a previous command making it necessary to slow
the whole schmear down a lot.)
Examples of hard disk mechanisms are:
Seagate ST-296-N (84.9Mb, 28ms, SCSI): This is a hard disk
mechanism that can seek in 28 ms, holds 84.9Mb, and, note
the "N" suffix, has an embedded hard disk controller (SCSI
type). This "N" series won't work at full speed I'm told.
Seagate ST-277-R-1 (65Mb, 28ms, RLL): This one can seek in
28ms, holds 65Mb, and, note the "R" in the name, is good
enough for RLL format, and doesn't have an embedded hard
disk controller.
Miniscribe M3650 (42Mb, 45ms, MFM): This one can seek in
45ms, holds 42Mb, and is _not_ good enough for RLL format;
it must be used with an MFM hard disk controller.
Miniscribe M3675 (64Mb, 45ms, RLL): This one can seek in
45ms, holds 64Mb, and is good enough for RLL format; you
can use an MFM or RLL hard disk controller. (You just lose
capacity if you use an MFM hard disk controller)
HARD DISK CONTROLLER: This is the device that takes the SCSI
commands (I'll only consider controllers that do take SCSI) and
actually makes the hard disk mechanism work. There are basicaly two
types to consider: MFM and RLL. An MFM controller takes SCSI commands
and works with the hard disk mechanism in MFM format, while an RLL
controller takes SCSI commands and works with the hard disk mechanism
in RLL format. (An MFM controller can use RLL hard disks, but just
can't make full use of the quality the disk offers, so you won't get
the full capacity. An RLL controller can _not_ use MFM hard disks,
they simply don't have the quality needed.)
Different controllers offer different features in addition to
the basic work horse stuff. Some can work with removable media hard
disks (the neato ones that use cartridge things), some can chain many
more disks to the same controller, etc.
Some companies that make controllers are OMTI and Adaptec. The
overwhelmingly popular controllers are from Adaptec. Here is a partial
list of what I believe they offer:
Adaptec 4000: This is an older MFM controller that can be bought
cheap. It can't handle removable media, but it can handle two hard
disks from the same controller.
Adaptec 4000A: This is a later version of the 4000 that can handle
removable media.
Adaptec 4070: This is an RLL controller. I think it can also, like
all Adaptec controllers (?), handle two drives from the same controller.
HOST ADAPTER: This is the key to allowing your Atari to speak
SCSI. The Atari DMA is very similar to SCSI, but not enough for SCSI
compatibility. A host adapter takes care of that by being a translator.
Three companies offer good adapters: Supra, Berkeley Microsystems
and ICD. However everyone I've talked to agrees that ICD is the way to
go. Supra has a bug that limits how far away you can have the hard disk
from the computer, while ICD doesn't and allows you to do read verifies.
I believe the ICD adapter can chain up to eight controllers and also has
another DMA port connection, so you can connect your laser printer or
whatever.
OTHER STUFF: Cables are a definite must to connect all the above
together. I'm not too sure about what kind are needed, but I'm sure
the literature you get from whoever sells the hard disk, the controller,
and the adapter will tell you what you need. I'm told that you need a
20 pin card-edge to header, a 34 pin card to card, and a 50 pin header
to header, but don't take my word on it.
A power supply is another must. At least 60W is recommended. Many
hard disks draw lots of power to start up, and if you expand later it's
best to have a power supply that can handle the job. Some people even
recommend 150W. (I guess they're cheap when bundled with an IBM case.)
After the all the above is set up and connected, you should have
a working hard disk, but many hard disks are hot running and could
overheat and many people just don't like to see all that stuff scattered
around on the desk, so a case and fan are good investments. These and
the power supply are very easy to find cheap. Many people just buy an
IBM PC case with power supply and fan all ready to go.
I'll now present some sample collections of hard disk, controller,
and adapter:
(Seagate ST-296-N) + (ICD host adapter)
This combination doesn't require a controller, because the Seagate
ST-296-N has an embedded controller. Because of the bug in "N"
series Seagates, this setup has to be slowed down to work. Also,
you couldn't just add another hard disk (unless it had an embedded
controller) without buying a controller.
($459 drive, $116 adapter)
(Seagate ST-4096) + (Adaptec 4000) + (ICD host adapter)
This combination is a fast high capacity (80Mb 28ms) system that
will easily expand by just plopping in another MFM hard disk
mechanism.
($520 drive, $110 controller, $116 adapter)
(Seagate ST-277-R) + (Adaptec 4070) + (ICD host adapter)
This combination is a fast high capacity (65Mb 28ms) system that
will easily expand by just plopping in another RLL hard disk
mechanism.
($349 drive, $125 controller, $116 adapter)
(Miniscribe M8450) + (Adaptec 4070) + (ICD host adapter)
This is an average (40Mb 45ms) RLL system that can be expanded
easily too.
($269 drive, $125 controller, $116 adapter)
(Seagate ST-225) + (Adaptec 4000) + (ICD host adapter)
This is a low end (21Mb 65ms) MFM system that can be made cheap,
but is still just as expandable as the rest.
($187 drive, $110 controller, $116 adapter)
(All drive prices from various ads in _Computer Shopper_.
controller and adapter prices from ad for D&P Computer in
_Current Notes_ Jan/Feb 1989)
So in summary, it would appear to me to be best to go with the
ICD host adapter, the Adaptec 4070 disk controller (RLL), and
some RLL type hard disk.
One company I find noteworthy here is Toad Computers. They sell
the ICD FA-ST hard drives, which use the ICD host adapter and,
I believe, the Adaptec controller and a Seagate hard disk.
Looking at their ad in _STart_, Sep 89, I see an 85Mb 28ms hard
drive for $739, a 20Mb 65ms hard drive for $499 and others
between that.
ADDRESSES:
Current Notes, Inc.
122 N. Johnson Rd.
Sterling, VA 22170
(703) 450-4761
(a very good ST mag for $24/yr. Vol. 9 No. 1 has a good
article about hard drives.)
D&P Computer
P.O. Box 811
Elyria, OH 44036
(216) 926-3842
(This company has lots of ICD and Adaptec stuff and cases
and such.)
Toad Computers
556 Baltimore Anapolis Blvd.
Severna Park, MD 21146
(301) 544-6943
(Absolutely the best buys for hard disks that I've seen.
They sell the ICD FA-ST hard drives.)
ICD, Inc.
1220 Rock St.
Rockford, IL 61101-1437
(815) 968-2228
(ICD makes the host adaptor that most people use. They also
make the FA-ST hard drives and other stuff.)
DISCLAIMER: I am in no way connected to any of the companies mentioned
above and I make no guarantees or assurances that any of the above is
true, useful, or safe, except that it can be used to decorate a paper
airplane.
Many thanks to:
Chris Freemesser
Peter Ikusz
Andy Cassino
Stephen Jacobs
Alan MacNeil
Michael Vishchers
Derrick
________________________________________________________________________
Scott Settlemier Univ. of Oregon scott@cie.uoregon.edu
The opinions expressed reflect in no way those of society.
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