Re: WTD: tandon 603s or 602s

From: Ethan Dicks (
Date: 2006-07-03 04:50:12

On 7/3/06, B. Degnan <> wrote:
> I just opened up the drive and found J14.  As I was about to cut J14 I
> decided that I am ready yet to make this change  ... I would rather try to
> find a 6 head drive first.  I am patient and I would like to get the full
> 7.5 MB's if I can.  I am not 100% sure that my ST-225 works, and then I
> would have circumcised the drive controller for no reason.  :-)

On my boards, at least, there's a 2-pin jumper - you can install it or
remove it as you wish.  Unlike the metaphor you describe, you _can_
"uncircumcise" a D9060.

> A while back I tried using a Miniscribe 3650 that I was given from a
> reliable source, who described it as working.  I read someplace that this
> drive was used to replace a tandon 603s successfully.  This drive has 6
> heads and 809 cylinders.

There's more to it than that... ST506 and ST412 interface drives hace
parameters like at what cylinder to reduce the write current to
prevent bleed-over and a timing thing called "write precompensation".
You have to ensure that the replacement mechanism performs the same
over the cylinders in use as a TM602S and TM603S.  I don't have the
relevant parameters memorized, but they can be found in tables of
ancient drives.  We all used to have to worry about all these numbers,
if the OS or the controller could be set to honor them, etc.

A Miniscribe 3650 _may_ be a match, but I have no experience with it.
The ST-225 _is_ a match and that's handy because Seagate made many
millions of them.

> When I format it starts out OK (you can hear the
> click click click for about a 1/2 hour, and then it just spins with no
> further format activity.  I am aware that it can take quite a while to
> format a d9090 drive, but after 5 hours I pulled the plug.

There are two different formatting times, depending on exactly which
ROM revision you have in your D9090.  I found an application note and
posted it once.  It describes that with a later version, the format
does indeed take hours and hours (3 for a D9060?), but IIRC, you
_should_ hear it ticking nearly all the time.

> Perhaps the drive had a defect.

Perhaps, but I'd expect it to halt and flash the LEDs, not fail silently.

> Is there a header command that stops the formatting
> process at a pre-defined number of cylinders?

The normal "N0:..." command does a low-level format, and the number of
cylinders is fixed in the ROMs (the D602S and D603S have the same
number of cylinders, but with 4 and 6 heads respectively).  That's why
you get 5MB out of a ~21MB ST225 - it ignores 75% of the drive.

> Do I understand correctly that the ST-225 is a straight substitute for the
> Tandon 602s D9060 "out of the box", and that no drive controller changes
> are needed?

That's my understanding from working with various folks 7 years ago on this.

> I will see if I can dig up a working 6-head ST 251.  I may also be able to
> get a Tandon TM603SE.


> One last question...I use this command to check the drive
> ?ds$
> I get the response code 73 and the DOS version.  Is there anything else I
> can do to make sure that the controllers are working?  Maybe I have been
> barking up the wrong tree.

If you get a message then the DOS board can at least talk IEEE.  No
guarantees about the SASI-processor on the board or the SASI<->ST506
bridge board.  Without a formatted HDA, I don't know that you'd be
able to prove the bridge card works.


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