Any place to buy a disc cartridge for an 1130

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Thomas Williams

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Jul 10, 2020, 11:02:42 PM7/10/20
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Deserve anyone know where to acquire a dish cartridge for an 1130?
I think it's a 2315 disk pack.
for a 2310 disk drive.

Also, does anyone have a spec sheet for same?
Does it hold about 1mb of data?

Thanks!

Tom Williams
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John Pierce

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Jul 10, 2020, 11:47:26 PM7/10/20
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IIRC< it was 510,000 16 bit words, and it spun at 1500 RPM.  The sector size was something odd like 320 words.   there was a constant number of sectors per track, it used 'hard sectored' timing, with sector timing slits cut into an aluminum ring on the hub.



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Tom Watson

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Jul 11, 2020, 1:57:54 AM7/11/20
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The 2315's were 4 sector disks (hard sectors). Other systems of the
era (and later when the capacity doubled for that size disk) were 16
sector disks (DEC used them for the pdp8 I believe), and 24 sector
disks (256 byte sectors) for the pdp11 (I believe that HP 2000 series
used these as well). The controller I helped build for a 32 bit
machine (SDS/Xerox Sigma 5) used the 24 sector ones and divided them
down to 6 sectors of 1024 bytes which the operating system liked
better. It was the mid 70's.

They may be aviable somewhere, but you need to be sure of the sector
count.


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Tom Watson <t...@johana.com>

Jeff Jonas

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Jul 11, 2020, 4:22:48 AM7/11/20
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>>> Also, does anyone have a spec sheet for same?

Everything you ever wanted to know about the IBM 1130
disk storage (but were afraid to ask):
http://www.ibm1130.net/functional/DiskStorage.html

The short-short of it:
- single 14 inch platter
- 203 cylinders (head positions): 200 used, 3 spares
- each cylinder is 2 heads: upper and lower
but normally treated as 8 sectors per track (4 upper platter, 4 lower platter).
I guess you could say the 3rd sector bit is head select.
- 321: 16 bit words per sector (first word is sector ID)

200 tracks * 8 sectors/track = 1600 sectors
x 320 data words = 512,000: 16 bit words


On Fri, 10 Jul 2020, Tom Watson wrote:
> The 2315's were 4 sector disks (hard sectors).
> Other systems of the era (and later
> when the capacity doubled for that size disk) were 16 sector disks

I wish I still had the Calcomp DS-12 manuals:
a 11 platter diskpack that emulated 5: 2315s at a time.
20 heads (one per useful surface).
Each surface was 16 sectors, emulating an entire 2315 disk.
A switch chose 5 surfaces at a time:
top 5, next 5, next 5, bottom 5.
Special software (and switch setting 5-6)
allowed accessing all surfaces.

> The controller I helped build for a 32 bit machine (SDS/Xerox Sigma 5)
> used the 24 sector ones and divided them down to 6 sectors of 1024 bytes
> which the operating system liked better. It was the mid 70's.

Very clever, particularly since 512 byte sectors
were the de-facto standard so so many years.
Hard drives are finally advocating large sectors for more capacity:
reducing space lost to each sector's pre-amble, post-amble and gap.

But then again, CP/M systems had a wide range
of floppy disk sector sizes from 128 to 2k.

-- fondly, jeff jonas

Carl Claunch

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Jul 11, 2020, 9:46:51 AM7/11/20
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Physically the disk was divided into 8 sectors with marks cut in the ring underneath, but the hardware in the 2310 drive attached to an 1130/1800 (and internal ramkit drive in the 1130) would divide by 2 and report only four sector marks per rotation.

If you look at documentation for the Diablo 31 disk drive, the specs for standard density are fully compatible with the 1130. Almost all of those drives you will find today, however, are the high density version that doubles the bit density and thus doubles the capacity of the pack. They were used in systems like the Xerox Alto and many other minicomputers. 

Carl
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