Deciphering an odd floppy disk format.
mattislind at gmail.com
Tue Feb 16 04:18:01 CST 2021
Den tis 16 feb. 2021 kl 03:16 skrev Fred Cisin via cctalk <
cctalk at classiccmp.org>:
> Thanks for the brochure.
> That looks like a fascinating project!
> Computerworld mentioned it occasionally in 1980.
> I love that "Pl/1 will soon emerge as the dominant language of
> If you haven't already exhausted such leads (apologies if you already
> have), some trivial GOOGLE'ing turned up the name (and autobiography) of a
> guy who designed one of their disk controllers:
I have seen them, except for that one. Quite a rambling story. I only
managed to read parts of it. Unfortunately there was little detail of what
he did, except that he did everything. A bit interesting to compare the Q1
Story with the one provided by Daniel Alroy.
The disk controller probably had some intelligence in itself. It seems to
have been connected over sync serial links to the computers. Probably it
provided a quite high level interface to the computer. When I analyzed the
tracks further I found that track 0 had 40 bytes sectors. Then there were
tracks that had 80 character sectors. These were mostly text data on these
tracks. A few tracks had sectors with 256 bytes. They seemed to contain
binary data. I assume track 0 contains the directory that tells what files
go where and the sector size on that track. Supposedly the intelligent
floppy controller (more like a file server) knows of the directory
structure and file structure of the various types of files there are.
In a sense this type of 80 characters record fits very well with classic
punch cards. Perhaps data entry was a big application?
This type of early distributed systems look a bit like the Cogar 4 /
Singer/ICL 1500 systems or Incoterm SPD 10/20. Intelligent terminals with
local storage connected to a central storage (file server).
> Sorry, NO technical details of the controller that he designed.
> On Mon, 15 Feb 2021, Mattis Lind wrote:
> > Well. Now this is NOT a standard 179x that has written this. As I
> > early on in this thread it was not at all possible to read the disks
> with a
> > standard controller. The bit rate was off by quite a bit and the general
> > format is different. So this is not necessarily a CRC at all. The machine
> > that has written these is the Q1 Lite computer. A very odd mid-seventies
> > system. http://bitsavers.trailing-edge.com/pdf/q1/Q1_Sales_Brochure.pdf.
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