Re: WTD: tandon 603s or 602s

From: B. Degnan (
Date: 2006-07-03 15:18:24

Thanks for answering my questions.  I realize that a lot of this stuff had 
been the subject of posts years ago, but for me it's new ground and I 
appreciate you're passing along your knowledge.

The miniscribe 3650 described in this thread _does_ blink an error after 
attempting to format for a 1/2 hour or so.  I was able to reproduce this 
effect again by attempting to format the same drive in an IBM XT last night.

My D9090 does not have the J14 2 pin jumper, it's a soldered wire.   I also 
tested my ST-225 - It's bad.  I do not have any other 6 head drives on hand 
that are not already committed to another system, I will attempt to get one 
and let you all know how it goes.  If I can't get an ST 251 or Tandon 603s 
to work, I will make the "snip" and go with the sure thing.


At 02:50 PM 7/3/2006 +1200, you wrote:
>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
>>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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