On Sep 5, 6:33*am, glen herrmannsfeldt <g... (AT) ugcs (DOT) caltech.edu> wrote:
Format-wise, are all double density (DD) 5.25 floppy drives the same,
or are there possible incompatibilities when reading a Synclavier
double density OS floppy on a third party 5.25 DD floppy drive ?

On 2008-09-09, Keoki <ofc.two (AT) gmail (DOT) com> wrote:
No, but since we're talking about 8" here, you'd be looking for an HD
5.25" drive rather than a DD drive.

Since I'm reading this on comp.sys.dec, I probably ought to point out
that there's a big difference between the way DEC did HD (RX31) and the
way IBM did it. A DEC drive will change speeds; at high density, it runs
at 360 RPM and it runs at 300 RPM at low density. An IBM-compatible drive
doesn't change speeds; it always runs at 360 RPM. This is why PCs have
to have three data rates: 500KHz (HD disk in HD drive), 300KHz (DD disk
in HD drive), and 250KHz (DD disk in DD drive).

3.5" drives always run at 300 RPM, which is why a high-density 3.5"
floppy has 1.44MB instead of the 1.2MB of the 5.25" drives.
--
roger ivie
rivie (AT) ridgenet (DOT) net

In article <6b8214b1-ad7f-4196-b4bd-8cf29df549ef (AT) r15g2000prd (DOT) googlegroups.com>,
Keoki <ofc.two (AT) gmail (DOT) com> writes:
I have seen numerous formats that were unreadable even at the sector level
on common 8" systems. Immediate examples that come to mind as Tektronix
Terminals (which could do CPM format but also had their oen format), Univac
UTS-100 and some of the older Word Processors, like Xerox. I am sure there
were many other incompatable formats as well. I have been called upon on
a number of occaisions to read (or try to read) old 8" disks as I still
have a number of different systems with working 8" floppies. It can be
an adventure!! :-)

bill

--
Bill Gunshannon | de-moc-ra-cy (di mok' ra see) n. Three wolves
billg999 (AT) cs (DOT) scranton.edu | and a sheep voting on what's for dinner.
University of Scranton |
Scranton, Pennsylvania | #include <std.disclaimer.h>

On Sep 8, 4:56 pm, Roger Ivie <ri... (AT) ridgenet (DOT) net> wrote:
The seller of the Synclavier system emailed he has a 5.25 DD operating
system floppy as well, so I *was* talking about reading a genuine 5.25
DD Synclavier floppy on a third party 5.25 drive. (A slight change of
topic, I guess :-)

He might have identified a 5.25 HD floppy wrongly as a 5.25 DD, but a
good third party 5.25 HD floppy drive will probably handle both HD and
DD formats, I presume. (I might be wrong.) The main gist of my last
question was if anyone knows whether it's possible to read a 5.25 DD
Synclavier floppy in a generic 5.25 drive, or do Synclavier floppies
use some peculiar sector size, allocation table, or whatever else that
prevents this.

Although Synclavier did built a lot of custom sound generating
hardware, I doubt they went into the costly floppy drive building
business too just for the sake of it; they probably used some third
party FD mechanism and relabeled it. Anyone knows?

Keoki wrote:

Format wise, all you need to know for the drive is DD or HD.
(SD will work in DD drive.) The drive converts the disk data
to a digital signal independent of the format. The controller
will have to understand the sector length and format, and there
are a few choices for those. Most systems use one of the
original IBM standards. Apple until they started using HD
disks had all their own formats. DEC used the IBM format
for single density, but their own special format for double
density.

The usual PC floppy controller will read a variety of sector
lengths, but not all software (OS) know how to do that.
That is, for making a bitwise (actually blockwise) copy
of a disk. Unix/Linux can usually do it.

I don't know this one at all.

-- glen

Keoki wrote:

http://www.mixfoundation.org/hof/04techof.html

seems to indicate 5.25in drive. That would have been
before HD, maybe even before DD.

-- glen

A hindsight note to those who might end up in a similar situation:
don't mess with a Synclavier. (Unless you don't care for it.)

I bought a well preserved 5.25 replacement FD mechanism that came from
an other Synclavier. Once we peeked into our Synclav floppy drive, we
discovered that even to swap this *genuine* mechanism isn't a plug and
play affair. A Synclavier tech will still have to redo some of the
electrical wiring for the slightly different replacement mechanism to
work with the enclosure and its red load button.

I was warned already that inside a Synclavier every single card,
memory chip and other doohickey is a world to itself, and often
incompatible with the same card or chip or doohickey in another
Synclavier of same year and model. Got that. But that even frigging FD
mechanisms differ from each other and require rewiring of the FD
enclosure... now who would have expected this. Apparently this is the
case.

So a word to the wise, if you think you can easily replace *any* part
in a Synclavier yourself, you are about to get more experience :-)
(And/or a big bill, like the one I'm about to get hit with)

Thank you all for your suggestions, though
Keoki

On Sep 16, 5:04*pm, glen herrmannsfeldt <g... (AT) ugcs (DOT) caltech.edu>
wrote:

Keoki wrote:

I would only recommend someone with some electronics experience
work on most electronic systems.
(snip)

I don't know about that one. I was suggesting a possible replacement
for the 8in drive that would use the same format on an HD 5.25in drive.
That may or may not be related to the official one. Even better
(easier to find) 3.5in HD.

-- glen