G'day Vrondi,
> Here's achallenge for this list: i picked up an old
> (20 meg I think) Seagate hard drive at a flea market for $5.
> It is the ST-225. Has a controller card with it.
> Now. What type of computer was this meant to run in?
[snipped]
This is an MFM-type hard drive. Parameters are:
cylinders - 615
heads - 4
sectors per track - 17
write precomp - 300
landing zone - 615
capacity - 21MB
interleave factor 3:1 (for low-level format)
The drive needs both a 34-wire and a 20-wire connector to the controller
card, which can support 2 MFM hard drives. The 34-wire is the control
cable for both drives (like a floppy drive cable) and the 20-wire is the
data cable (one per drive).
ST-225s were designed to run in XT-class computers so you may need to
tell your 486's CMOS setup that the hard drive is "not installed". At
least this was the case in one of my 386's - but another 386 was quite
happy running the same drive/controller as hard drive "Type 2". It
seems to depend on how well the motherboard BIOS gets on with the
controller BIOS. As to why it's not working for you:
- are the controller card's settings correct for this drive? Most cards
would support popular 5MB, 10MB or 20MB drives through jumper switches,
but some cards were also programmable via software. If the drive & card
came together from a working system you can assume the jumpers are set
okay. The ST-225 was a popular model so chances are good that your
controller may specifically support it.
- are the drive cables plugged in correctly? A common error in
single-drive systems was to plug the 20-wire cable into the card via the
connector for the _second_ drive (sometimes the labelling was
nonexistent). As for the 34-wire cable, the connector furthest from the
card goes to the first (or only) hard disk.
- is the drive properly formatted? MFM drives can be low-level
formatted using the DOS Debug utility. Get into Debug, then type in the
command "g=c800:5" (or "g=c800:6") to start the controller's built-in
formatting program. Some of these even came with a menu of popular
drive models - just pick yours and go! After you do the low-level
format, use the DOS Fdisk and Format commands to make the drive useable.
- some people tried to format their ST-225s as "RLL" drives with more
sectors per track. This trick sometimes worked and gave up to 30MB
capacity but long-term data stability was dodgey. I recall one such
system lost its DOS whenever the ambient temperature rose over 40C.
Genuine Seagate RLL drives have an "R" appended to the model number.
You will need an RLL controller to get full capacity; but there's no
harm in formatting an RLL drive as an "MFM" (with an MFM controller).
- is it mechanically okay? For all you know, the bearings may have
siezed, or the read/write heads may be stuck to the disk platters.
Or the stepper motors may have blown, or...
- I think the Tandy 1000s needed proprietary hard disks? I can't recall
if it was a non-standard interrupt or wierd I/O port or if the connector
wiring was a bit strange. Ask your Tandy/Radio Shack dealer if he has
any specifications.
A drive of this vintage will work fine with DOS 3.3. You should also
acquire a "disk parking" program to be run just before you turn off the
computer; to prevent the read/write heads crashing into the disk
platters. If you can't find such a program I've written a simple one
which works for my old hard disks.
cheers,
Fraser Farrell
http://www.dove.net.au/~fraserf/
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