21 May
2006
21 May
'06
4:06 p.m.
All:
I have several random parts I'm going to pull together to build
a "new" floppy system for my IMSAI. I have an SD Sales Versafloppy
controller card (which used the FD1771B controller) and several 5.25" floppy
drives (all soft sectored). The Versafloppy manual indicates that it will
work with a Shugart SA400/450. When I look up the specs on the SA400, it
indicates that the unformatted capacity is 109.6k and the formatted capacity
is 81k. I didn't read the entire manual but this look like SSSD specs.
I of course don't have any floppy drives like this but I have
several original PC drives (TM-100 and others) and several 360k drives of
various types.
The question is this: can I use these later drives on this
controller without problems? If there are problems, what might they be?
Thanks.
Rich
Rich Cini
Collector of classic computers
Build Master for the Altair32 Emulation Project
Web site: <http://highgate.comm.sfu.ca/~rcini/classiccmp/>
http://highgate.comm.sfu.ca/~rcini/classiccmp/
/************************************************************/
21 May
21 May
4:49 p.m.
hi Richard
I think the 450 is at least double sided if not double density.
In any case, a 360K drive can be used as a single sided single
density disk, without any issues that I know of. The 400 was
a 35 track machine but you can get more tracks on the
360K drives. These are 40 tracks.
I've been using some 360K drives on my H89 for years as 35
track single sided single density but also hard sectored.
Does the VeriFloppy support MFM?
Dwight
From: "Richard A. Cini" <rcini at
optonline.net>
Reply-To: "General Discussion: On-Topic and Off-Topic
Posts"<cctalk at classiccmp.org>
To: "'General Discussion: On-Topic and Off-Topic
Posts'"<cctalk at classiccmp.org>
Subject: Building new S100 floppy system
Date: Sun, 21 May 2006 12:06:11 -0400
All:
I have several random parts I'm going to pull together to
build
a "new" floppy system for my IMSAI. I have an SD Sales Versafloppy
controller card (which used the FD1771B controller) and several 5.25"
floppy
drives (all soft sectored). The Versafloppy manual indicates that it will
work with a Shugart SA400/450. When I look up the specs on the SA400, it
indicates that the unformatted capacity is 109.6k and the formatted
capacity
is 81k. I didn't read the entire manual but this look like SSSD specs.
I of course don't have any floppy drives like this but I have
several original PC drives (TM-100 and others) and several 360k drives of
various types.
The question is this: can I use these later drives on this
controller without problems? If there are problems, what might they be?
Thanks.
Rich
Rich Cini
Collector of classic computers
Build Master for the Altair32 Emulation Project
Web site: <http://highgate.comm.sfu.ca/~rcini/classiccmp/>
http://highgate.comm.sfu.ca/~rcini/classiccmp/
/************************************************************/
5:14 p.m.
Richard, the Versafloppy was a fine controller for its day. Because of
the 1771, it's limited to FM, and IIRC, doesn't do DMA transfers.
Originally, these things were specified on single-sided media for 35
tracks. Any 5.25" 360K floppy drive can be used, provided it furnishes a
READY signal--I don't recall if the Versafloppy included a optional
on-board ready circuit, but it's simple enough to derive a READY signal
using a couple of one-shots if your drive doesn't support one. You can use
a full 40 tracks, or, alternatively, find a 720K drive like a Teac FD55F,
and use 80--the 1771 doesn't care how many tracks you're using.
Now, here's where my memory begins to fail after about 25+ years. I don't
recall if the Versafloppy has a head-select register or not. The 1771 has
no head-select logic on it, so a bit from an external latch has to furnish
the signal--it seems to me that it does, but my mind could be playing
tricks.
If you wanted to try your hand at MFM, you could, with only a very few
board changes, use a WD 2791 (which has its own data separator and head
select logic on chip) which would give you both FM and MFM. Another option
might be a WD 1791, but you'd have to furnish your own data separator for
MFM. I wouldn't attempt this without a fast-enough CPU, however. A 4 MHz
Z80 should be fine.
Hope this helps.
Cheers,
Chuck
P.S. For whatever reason, I sold the VF to a friend and bought a Tarbell
controller. Still didn't do MFM, but I liked it better for some reason
that now escapes me.
On 5/21/2006 at 12:06 PM Richard A. Cini wrote:
All:
I have several random parts I'm going to pull together to
build
a "new" floppy system for my IMSAI. I have an
SD Sales Versafloppy
controller card (which used the FD1771B controller) and several 5.25"
floppy
drives (all soft sectored). The Versafloppy manual indicates that it will
work with a Shugart SA400/450. When I look up the specs on the SA400, it
indicates that the unformatted capacity is 109.6k and the formatted
capacity
is 81k. I didn't read the entire manual but this look like SSSD specs.
I of course don't have any floppy drives like this but I have
several original PC drives (TM-100 and others) and several 360k drives of
various types.
The question is this: can I use these later drives on this
controller without problems? If there are problems, what might they be?
Thanks.
Rich
Rich Cini
Collector of classic computers
Build Master for the Altair32 Emulation Project
Web site: <http://highgate.comm.sfu.ca/~rcini/classiccmp/>
http://highgate.comm.sfu.ca/~rcini/classiccmp/
/************************************************************/
6:49 p.m.
All:
I have several random parts I'm going to pull together to build
a "new" floppy system for my IMSAI. I have an SD Sales Versafloppy
controller card (which used the FD1771B controller) and several 5.25" floppy
drives (all soft sectored). The Versafloppy manual indicates that it will
work with a Shugart SA400/450. When I look up the specs on the SA400, it
indicates that the unformatted capacity is 109.6k and the formatted capacity
is 81k. I didn't read the entire manual but this look like SSSD specs.
The 1771 is a single density (FM) controller only.
I of course don't have any floppy
drives like this but I have
several original PC drives (TM-100 and others) and several 360k drives of
various types.
The question is this: can I use these later drives on this
controller without problems? If there are problems, what might they be?
It's almost impossible to make a drive that will handle double density
but not single density. So your '360K' drives will be fine in that
respect.
There are likely to be 2 other differences :
1) The SA400 was, IIRC, a single-sided unit. Your 360K drives are double
sided. The controller may well not support double-sided operation, and it
may use the side select pin for something else (DS3 was one common use I
think). You may need to do a little bit of modification in this area.
2) I think the SA400 was a 35 cylinder drive, '360K' drives are 40
cylinder. This shouldn't matter unless, for some unknown reason, the
controller only sends 35 step pulses when it tries to restore to cylinder
0. AFAIK any standard use of the 1771 won't suffer from this.
-tony
9:09 p.m.
Dwight, Chuck, Mike, Tony:
All of this has been very helpful. Thanks a lot.
I would think that since the 1771 is an FM controller I won't be
able to go cross-platform (i.e., using a PC) to create or image diskettes.
If this is true, then is there a "better" S100 floppy controller I should
hunt for?
Rich
-----Original Message-----
From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org]
On Behalf Of Tony Duell
Sent: Sunday, May 21, 2006 2:50 PM
To: cctalk at classiccmp.org
Subject: Re: Building new S100 floppy system
All:
I have several random parts I'm going to pull together to
build
a "new" floppy system for my IMSAI. I have
an SD Sales Versafloppy
controller card (which used the FD1771B controller) and several 5.25"
floppy
drives (all soft sectored). The Versafloppy manual
indicates that it will
work with a Shugart SA400/450. When I look up the specs on the SA400, it
indicates that the unformatted capacity is 109.6k and the formatted
capacity
is 81k. I didn't read the entire manual but this
look like SSSD specs.
The 1771 is a single density (FM) controller only.
I of course don't have any floppy
drives like this but I have
several original PC drives (TM-100 and others) and several 360k drives of
various types.
The question is this: can I use these later drives on this
controller without problems? If there are problems, what might they be?
It's almost impossible to make a drive that will handle double density
but not single density. So your '360K' drives will be fine in that
respect.
There are likely to be 2 other differences :
1) The SA400 was, IIRC, a single-sided unit. Your 360K drives are double
sided. The controller may well not support double-sided operation, and it
may use the side select pin for something else (DS3 was one common use I
think). You may need to do a little bit of modification in this area.
2) I think the SA400 was a 35 cylinder drive, '360K' drives are 40
cylinder. This shouldn't matter unless, for some unknown reason, the
controller only sends 35 step pulses when it tries to restore to cylinder
0. AFAIK any standard use of the 1771 won't suffer from this.
-tony
9:41 p.m.
On 5/21/2006 at 5:09 PM Richard A. Cini wrote:
I would think that since the 1771 is an FM controller
I won't be
able to go cross-platform (i.e., using a PC) to create or image diskettes.
If this is true, then is there a "better" S100 floppy controller I should
hunt for?
Not necessarily--try out the testsd.exe utility on your PC at:
www.sydex.com/download/testsd.exe
It'll tell you very quickly if your PC can write FM diskettes. If you've
got several machines to try, just make a 3.5" DOS boot floppy with
testsd.exe on it. Testsd uses the last couple of cylinders on the
diskette, so you have a quick "boot and test" solution. My experience
tells me that later (post 1999) PCs generally have a better probability of
supporting FM than earlier ones. Go figure.
But if you want to write MFM, you can either modify the board you have or
glom onto something like one of the CompuPro controller boards.
Cheers,
Chuck
9:48 p.m.
If the system gives you any choices for disk format parameters,...
The most common 5.25" SSSD format is that of the Osborn.
10 sectors per track, with 256 bytes per sector.
10:35 p.m.
On Sunday 21 May 2006 05:48 pm, Fred Cisin wrote:
If the system gives you any choices for disk format
parameters,...
The most common 5.25" SSSD format is that of the Osborn.
10 sectors per track, with 256 bytes per sector.
I don't recall the SPT offhand, but the Osbornes used 1024-byte sectors.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
10:57 p.m.
The most
common 5.25" SSSD format is that of the Osborn.
10 sectors per track, with 256 bytes per sector.
I don't recall the SPT offhand, but the Osbornes
used 1024-byte sectors.
The Osborne SD was 10 SPT, with 256 bytes per sector.
The Osborne DD was 5 SPT, with 1024 bytes per sector.
11:51 p.m.
On 5/21/2006 at 3:57 PM Fred Cisin wrote:
The Osborne SD was 10 SPT, with 256 bytes per sector.
...and, for single-density 5.25" media, that's about as good as it gets.
256 bytes per sector means that you'll have to transfer a sector and
deblock on read or block on write. Perhaps the TRS-80 Mod I Omikron CP/M
with 18 128-byte sectors might be easier to program--a similar format was
used by the Xerox 820 for 5.25" media.
FWIW,
Chuck
22 May
22 May
4:19 a.m.
On Sunday 21 May 2006 06:57 pm, Fred Cisin wrote:
That may be the source of the confusion, I saw a fair number of those
machines, since we had our shop in a building where the landlord was an
Osborne dealer, but I almost never saw a SD machine.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
> The most
common 5.25" SSSD format is that of the Osborn.
> 10 sectors per track, with 256 bytes per sector.
On Sun, 21 May 2006, Roy J. Tellason wrote:
I don't recall the SPT offhand, but the
Osbornes used 1024-byte sectors.
The Osborne SD was 10 SPT, with 256 bytes per sector.
The Osborne DD was 5 SPT, with 1024 bytes per sector.
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