Subject: Re: 8.5" drive for 11e
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From: apple2pd@ground.ecn.uiowa.edu (ISCA AppleII Librarian)
Newsgroups: comp.sys.apple2
Date: 1 Apr 1999 17:14:11 GMT
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From article <1257184090-990331052400@rook.wa.com>, by brian.hammack@rook.wa.com (Brian Hammack):
>  Doug chanted almost zenlike:
> 
>  DC(| There were quite a few 8" drive controllers around for the apple
> 
> I'd heard this before.  :)  My question is, how much data does an 8"
> disk hold?  [5.25" = 140k, 3.5" = 800k]
> 

It depends, but 256K per disk is the safest answer, for IBM 3740 Format.

My 8" setup had the SVA DISK 2+2 controller with Shugart SA800/801 drives.
It could handle four drives under Apple Dos3.1 or 3.2  (also Apple Pascal
and Dos3.3.  Note: unlike DiskIIs, capacity did not change between Dos3.2
and dos3.3 or Pascal.)

IBM 3740 format:  77 Tracks
                  36 Sectors/Track
                 128 Bytes/sector
               ============
               256,256 bytes total (2.2 times the capacity of dos3.1/3.2
diskII)  Recording technique was FM, single density.

The SA800 drives were single sided, the SA850 drives were double sided, with
twice that capacity, but I don't think the Disk2+2 controller supported
double sided disks.

Thus, SVA introduced the ZVX4 Megabyter controller.  It supported 1 and 2
sided disks and single and double sided disks.  So with a ZVX4 controller:

                        SA800    SA850      SA800    SA850
Format
  Tracks                  77     154          77      154  
  Sectors/track           26      26          48       48
  Bytes/sector           128     128         128      128
  Recording technique     FM      FM         MFM      MFM

  Density                Single  Single      Double   Double
  Heads(sides)             1       2           1        2
  Media (IBM diskette)     1       2           1D       2D
  Storage/drive (bytes)  256k    512k        473k     946k
  Max # drives             4       2           4        2
  Max storage/ZVX4      1024k   1024k       1892k    1892k
  Data transfer rate     250k    250k        500k     500k

(Date transfer is Bits/second, not "bytes/sec")

So in re-answering your original question: 256k, 473k, 512k, or 946k
were the capacities for 8" diskettes.

But at that time 256k/disk was a dream for Apple Pascal programming.
All system files from Apple0:, Apple1:,  needed Apple2: and Apple3: fit on
the boot system disk, and my programs fit on a second disk on a second
drive.  No floppy shuffle.  It was nice.

Later,
  --Steve


-- 

 --Steve  (apple2pd@ground.ecn.uiowa.edu)