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32-sector 8" Floppy Disk - 3M 740-32

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pbirkel@gmail.com

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This brand of 8" floppy disk is described as "Single-head, single-side, 32 sector, single-density".

I presume that these would be 256KB capacity, IBM-original design.

What drives would have been used with these, and what S-100 controllers, if any?

I'm thinking that the SA-801 drive would have worked with them?

Yes, I'm new to hard-sectored floppy drives ... so thanks for your forbearance!

-----
paul
 
The Altair (MITS) floppy drive uses 32 hard sector 8" disks. It's a fairly tight format that crams 329K onto the disk (includes meta data, payload data alone totals 308K). Wang word processing systems used the 32 hard sector disks as well.

The diskettes will work in an 800 or 801 drive - the requirement for the 801 drive depends on the controller. The additional components installed on the 801 drive are used to separate the index pulse from the sector pulses (index pulse only on the index line pin 20, and sector pulses sent on pin 24). The Altair controller does the separation of index and sector pulses itself and expects all 33 pulses to come in on the index line, pin 20. The 800/801 jumper on an 801 drive will make the 801 drive function like an 800.

Mike
 
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I've seen the 32-hard-sector disks occasionally used as soft-sector ones. Most 8" floppy drives will separate the index from the sector pulses and put them on separate output pins. If your soft-sector controller doesn't connect to the SECTOR pulse on the 8" drive, you'll never know the difference.

This can occasionally throw you if someone sends a hard-sector disk for conversion and it turns out to really be a soft-sector format.

As far as I'm aware, 32-sector is the only hard-sectored 8" diskette format. Drives can be jumpered to divide this down to 16 or 8 sectors, but the same disk is used.

The only exception that I can think of are the very ancient Memorex and IBM drives using disks with sector holes punched in the outer edge of the cookie (8 of them). Those are pretty rare to find in the wild today.
 
Chuck(G) said:
I've seen the 32-hard-sector disks occasionally used as soft-sector ones. Most 8" floppy drives will separate the index from the sector pulses and put them on separate output pins. If your soft-sector controller doesn't connect to the SECTOR pulse on the 8" drive, you'll never know the difference.

This can occasionally throw you if someone sends a hard-sector disk for conversion and it turns out to really be a soft-sector format.
Click to expand...

Cute; I'll need to keep that in mind.

Chuck(G) said:
As far as I'm aware, 32-sector is the only hard-sectored 8" diskette format. Drives can be jumpered to divide this down to 16 or 8 sectors, but the same disk is used.
Click to expand...

The floppies that I have here appear to have been used in a MetaList CNC Lathe, judging by the hand-labels. Nothing else remarkable about them other than they don't appear to be shedding or otherwise particularly aged.

Chuck(G) said:
The only exception that I can think of are the very ancient Memorex and IBM drives using disks with sector holes punched in the outer edge of the cookie (8 of them). Those are pretty rare to find in the wild today.
Click to expand...


I have some that are marked "Vydec Compatible" and have a big rectangular chunk missing from a corner along the head-slot end (I guess to keep the user from inserting upside-down). They are hard-sectored on the outer-edge; probably 32 sectors. Guess that that they are the ones that you're thinking of as it seems that they were intended for the Memorex 651. Excellent technical description at:

http://www.computer.org/csdl/proceedings/afips/1974/5082/00/50820545.pdf

So much to learn ...
 
pbirkel@gmail.com said:
This brand of 8" floppy disk is described as "Single-head, single-side, 32 sector, single-density".

I presume that these would be 256KB capacity, IBM-original design.

What drives would have been used with these, and what S-100 controllers, if any?

I'm thinking that the SA-801 drive would have worked with them?

Yes, I'm new to hard-sectored floppy drives ... so thanks for your forbearance!

-----
paul
Click to expand...
Mike has covered the 8” floppy drive information. I have attached the 1983 3M Diskette Reference Manual. Required Primer for newcomers to 1970s and 1980s Computer Media for Floppy Drives.

Greg
 

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Chuck(G) said:
Did 3M ever make floppies for the Memorex 651? I don't think they ever made 3.25" disks nor disks for the 5.25" Drivetec/Kodak drives.
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3M did make floppies for every 8 inch drive type, till early 1980s.
PAGES 21 and 22 of the 1983 3M Catalog, that I previously posted — should answer your question.

For the special 5.25 inch drive requirements (hard sector, etc.) —
it largely depended on manufacturers (and market size).
3M was a client (my firm) during 1990s … and I used almost all of their products in 1970s/1980s

Memorex 651 (1977) used hard sector (32 holes) 8” floppy disks (Memorex produced original media).
Rotation Speed (375 rpm) and Keying Notch did NOT follow IBM standard.

Have you called Floppy Disk: https://www.floppydisk.com/
When I talked to him (January) for my 8” floppy order, he noted he had a large variety from that 1970s era.
 

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No, I said "3.25 inch" floppies. I have drives and disks, and the only brand I ever saw on the disks was Dysan. I believe that they gambled on the format and lost a pile of money when the 3.5" format was adopted. Similarly, for the 5.25" 3 and 6MB floppies for Kodak/Drivetech, the only vendor I've seen was Verbatim, but I suppose 3M might have made some also.
 
Chuck(G) said:
No, I said "3.25 inch" floppies. I have drives and disks, and the only brand I ever saw on the disks was Dysan. I believe that they gambled on the format and lost a pile of money when the 3.5" format was adopted. Similarly, for the 5.25" 3 and 6MB floppies for Kodak/Drivetech, the only vendor I've seen was Verbatim, but I suppose 3M might have made some also.
Click to expand...
Yes, there was a couple different 3 inch formats (Sony pushed one in Japan, a couple of years).
Tandy and NCR … jumped on the 5.25” QD/DS drives … by 1984 IBM AT introduced HD/DS that killed it.

There was also the LS120 … that 3M pushed, but died by end of 1990s
 
Let's not forget the Micropolis 100 tpi 5.25" format. 77 tracks, but placed more toward the outside edge of the cookie. In 3.5" there's a huge amount of variety that never made it. Caleb UHD144 format, for example. Or the Brier 20MB scheme. I have a DTC TakeTen 5.25" drive still in its shrinkwrap--never have located any media for it.

The possibilities are endless...
 
Necro-posting a bit, but I forgot to mention 8" floppies for the Wang 2200. Unlike just about all common (except for the Memorex 650 floppies) 8" hard sector media which are punched for 32 sectors (33 holes), the Wang 0063 floppies for the 2270 drive use a 16-sector 8" (17 holes) disk.

Just want to keep the record straight.
 
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