>>> 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):
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