22 Jul
2004
22 Jul
'04
3:38 a.m.
Message: 1
Date: Tue, 13 Jul 2004 17:32:21 +0800
From: Wai-Sun Chia <waisun.chia(a)hp.com>
Subject: CDC 9762 vs. RM02/03?
To: General(a)caspar.my.cpqcorp.net,
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<cctech(a)classiccmp.org>
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I have some conflicting info here. On one hand the literature says that
DEC rebadged the CDC9762 as RM02 and RM03s...
Rebadged and had modified (CDC supplied a slightly modified SMD
interface for DEC to interface to.
OTOH, the CDC has a SMD interface yet the RM02/03 has a
MASSBUS interface.
The SMD interface (modified by DEC) goes to a Massbus adapter
housed in the drive cabinet under the drive.
DEC also used a similar technique on RP04/5/6's which used a
DCL (Drive Controller Logic IIRC) to interface to the Massbus
from the internal drive logic levels.
DEC modified the SMD signals on the RM02/RM03/RM05 to make them
slightly different from standard SMD versions and they also used
the CDC high altitude heads to reduce crashes.
Furthermore, the CDC is listed to be at 80MB, yet the
RM02/03 apparently
has 67MB only.
RM02/RM03 is 80mb unformatted 67 formatted. CDC sold the drive
which could be set to many different sector sizes and sector counts
per cyl.
So the DEC was 31 or 32 (IIRC) sectors of 512 bytes per track.
CDC topped out with 33 sectors...
IBM Series 1 systems I worked on used 256 byte sectors IIRC.
So, which is true? I'm confused.
Thanks.
/wai-sun
Bill Pechter
ex-DEC Field Service
--
Bill Pechter
Systems Administrator
uReach Technologies
732-335-5432 Office
877-661-2126 Fax
877-661-2126 uNumber
23 Jul
23 Jul
3:31 p.m.
On Thu, Jul 22, 2004 at 11:38:19AM -0400, Bill Pechter wrote:
DEC modified the SMD signals on the RM02/RM03/RM05 to
make them
slightly different from standard SMD versions and they also used
the CDC high altitude heads to reduce crashes.
I didn't know about the high altitude heads. That's an interesting
tidbit.
RM02/RM03 is 80mb unformatted 67 formatted. CDC sold
the drive
which could be set to many different sector sizes and sector counts
per cyl.
So the DEC was 31 or 32 (IIRC) sectors of 512 bytes per track.
CDC topped out with 33 sectors...
A-ha! That makes perfect sense. With a bit of googling (RM02, RM03,
9762 and cylinder), the first hit is http://www.inwap.com/pdp10/usenet/disks
In the article, among other disk sizes, the RM02/RM03 is 823 cyls, 5 heads,
32 sectors/track - 67,420,160 bytes (33 s.p.t is 69,527,040, meaning that
there must be a bit of overhead compared to the 80MB unformatted capacity).
-ethan
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