Re: Pascal 400kb Disk

[apple2pd@ground.ecn.uiowa.edu (ground.ecn AppleII Librarian)]

In article <R72dnTzSifVmXvWjXTWcoA@comcast.com>,
Bill Garber <willy46pa@comcast.net> wrote:
>
>I believe what everyone is missing here is this. These are 400K disks.
>They are probably only written on one side. The Apple 3.5 drives
>will only do double sided disks. 800k, am I wrong here? You need the
>older Mac drive, the 400K single sided drive that was used on the
>Mac 512's. Is this correct? I'm not altogether certain of what I'm saying
>but if I'm right then it may be impossible to copy those disks without
>one of these drives, which are sometimes on eBay, although I've only
>seen 2 in like 8 months. Maybe someone like AllTech has one lying
>around. Just a thought.
>

My $0.02 of FYI to confuse the isssues:

A 400K 3.5 disk (ala old Mac 400K drive) is a single-sided disk.  (And no,
you can't punch a hole and insert it upside down to use the other side.)
A regular 800K drive will read it.  Davex even lets you format a disk as
400K.  On a Mac128K, the disk was organized as MFS, not HFS.  At some
point in MacOS, Apple stopped supporting MFS file system.

Supporting testimony:  I used to have a II+ and a IIe setup with UDC
controller cards and Mac400K drives, using ProDOS.  I could use the disks
in my 800K drives on another IIe or my IIGS to read/write files and then
use the files on the 400K drives.  I could format the disks in either the
400K drive, or in the 800K drive using Davex to format single-sided.
Nothing was special about 400K disks except that they were single-sided.

Apple Pascal:  After Pascal 1.3 came out which supported 3.5 drives
directly, Apple released in a tech note details on how to use 800K disks
as two 400K Pascal volumes.  I didn't decipher the algorithm, but I think
one 400K was one side, and the other 400K was on the other side.  But they
could have split the disks into two logical halves using the first 800
blocks for vol1 and the next 800 blocks for vol2.  I don't think this is
the same as side1 and side2. 

If this is Apple Pascal 1.2 or earlier, the company selling the drive
would have had to furnish the drivers for the controller and drive.  No
good standard  existed on how the disk should be structured.  But a
block-reader should be able to read blocks, and the blocks would comprise
1 or two sectors most likely.

I think early Pascal versions for the Mac (128K) would have come on 400K
disks (for the early 1-sided drives).  Perhaps this is a Mac Pascal disk?

I have several Mac400K drives.  By now the grease is dried up so they
don't eject disks easily, but relubing lightly solves that problem (I had
to do that when I started using them on the Apple IIs).  The UDC is the
only controller I know that will work with them on a Apple II.  I don't
think the UDC works in a IIGS.  You need a II+ or IIe. [Make $offer]

One of my earlier flagship computers was a II+, 64K, 288K Flashcard
(memory), Videx 80-col, UDC+2 400K drives, 2 5.25 DISK II, Mountain
Computer Apple Clock, etc. running AppleWorks (v2.0?) with PlusWorks.  On
a II+ !  7th heaven.

  --Steve

-- 

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