Olivetti 3MB ST506-interface drive?

dwight dkelvey at hotmail.com
Sun Mar 13 20:17:25 CDT 2016

I don't recall how many heads a ST506 had. I have one on my NC4000,
home brew, machine. I recall picking the drives up at garage sales because
DOS no longer supported them, only being 5Meg.
Next time I at my storage, I can being my machine home and power it up.
I suspect it has the setup information in my source code.
I used an old XT HD controller card for the hard drive and a XT floppy card
for the floppy. I disabled the EPROM on the HD card because it was
useless for the NC4000.
The M20 used the 11Meg ( I guess formatted 10 Meg ) drives. I used a
ST251 because it had the same number of heads (6) and RPM speed as
the Olivetti drive used. It had more cylinders but that wasn't an issue.


From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Fred Cisin <cisin at xenosoft.com>
Sent: Sunday, March 13, 2016 3:13 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Olivetti 3MB ST506-interface drive?

Is that "3MB" FORMATTED, or UNFORMATTED capacity?

"10MB" (ST412) was 12MB unformatted, with 306 cylinders and 4 heads.
"5MB" (ST406) was 6MB unformatted, with 306 cylinders and 2 heads. or was
it (St506?) 153 cylinders with 4 heads?

In any case, using half as many heads/surfaces would create an "ST503"
drive.  about 2.5M formatted capacity.

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