[Simh] Cray X-MP simulator and OS image

[Michael Mondy]

On Fri, Jun 28, 2013 at 11:16:05AM -0700, Al Kossow wrote:
> On 6/28/13 10:46 AM, Michael Mondy wrote:
> 
> >It includes efforts that he and others performed to read a disk platter without a working drive
> 
> no, he borrowed a CDC 9762 drive and used the read amps in it
> what wasn't known was the track format.

Agreed.

I didn't mean to imply he didn't use a drive; just that unusual efforts were used.  The drive wasn't really working in the way it was designed to be used.  He used the head, but he didn't use the drive's positioning mechanisms.  From his web page:

-- Quote
I built a robot that would manually move the head forward 1/5200th of an inch at a time (there are 400 data tracks per inch, so this gives me a whopping 13 steps per data track!), while a high-speed analog-to-digital converter would take the analog signal straight from the drive's read amplifier and buffer it into an FPGA at a blistering 80 million samples-per-second (like I said earlier, the theme here was overkill... the data was only changing at ~10 MHz or so). 
[snipped]
Remarkably enough, this scheme actually worked pretty well. It took about three or four hours, but I was able to image the entire disk pack. Of course, that left me with a 35 gigabyte magnetic image of the disk.
-- End quote

I imagine similar efforts have been done by others, but this is an interesting writeup.

-- Mike