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pbirkel@gmail.com
September 29th, 2015, 11:06 AM
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!

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paul

deramp5113
September 29th, 2015, 01:56 PM
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

Chuck(G)
September 29th, 2015, 10:12 PM
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 [b]outer[b] edge of the cookie (8 of them). Those are pretty rare to find in the wild today.

pbirkel@gmail.com
September 30th, 2015, 04:19 AM
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.

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


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 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.


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

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 ...

Chuck(G)
September 30th, 2015, 08:37 AM
Yup, the Memorex 651 was the drive I was thinking of.