DEC Gamma-11 units in private collector hands?

Philippe Vachon philippe at
Sat Oct 27 10:48:28 CDT 2007

On Sat, Oct 27, 2007 at 12:06:42AM +0100, Tony Duell wrote:
> I don't have one, but I did repair one about 10 years ago (it was still 
> being used for 'real' work back then), so I have some idea as to what was 
> inside. I never worked on the camera side of things, so I can't comment 
> on that.
> The machine consisted of a normal 11/34 processor (I can't rememebr if 
> there was a floating point oard in it or not) with a grpahics display 
> system, I think it was a VS60. There was an RL11 disk controller linked 
> to (IIRC) a single RL01 drive.
> There was also a 5.25" high expanison box. This contains 2 4-slot 
> backplanee. One was Unibus, linked to the 11/34 Unius, and contains (IIRC 
> again) the RL11 and the Unibus end of a DW11-B. The other was Q-bus, and 
> contains the other end of the DW11-B. It also contained 3 special Qbus 
> cards which were the interface to the camera. I probably took copies of 
> the printsets for those, but don't expect me to find them in the near future.
> The only part I had to repair was the RL11, that was standard. So alas I 
> didn't get to look at any of the 'interesting' bits.
> -tony

Hrmn, this is interesting; I wonder why DEC chose to use an 11/34 for
the Gamma-11, or if the machine was "upgraded" to become a Gamma-11
post-installation. I'm fairly tempted to try to pick up that boardset,
nonetheless... I imagine it is rather difficult to snag anymore though.

Thanks for the details, Tony!

> <snip>
> I don't recall from having not reread this whether this was a PDP-11 
> instrument or not, however, but this certainly remindes me of this.
> Jim

Yeah, these were PDP-11s, as I recall. In skimming the article, that
seems to be what it indicates as well. I can't help but to feel sorry
for the people who were overexposed to radiation in the Therac-25, but
I get the impression that the lesson from it has been learned, but only
after prolonged time in court.


More information about the cctech mailing list