PDP-12 Restoration at the RICM

Rich Alderson RichA at LivingComputerMuseum.org
Mon Aug 17 13:51:11 CDT 2015

From: Jay Jaeger
Sent: Sunday, August 16, 2015 3:18 PM

On 8/16/2015 9:00 AM, Michael Thompson wrote:

>> We did a lot more debugging on the TC12 LINCtape controller.

> Second gut hunch is that it would be hard to see how the drive could
> cause this UNLESS the TC12 uses one side of the redundant tape channels
> in one direction, and the other side in the other direction.

Not possible.  The *drive* wire-ORs the redundant channels, before the
data goes into (or after it comes out of) the controller.  *That's* the
redundancy.  When reading in the reverse direction, only the mark tracks
on a DECtape read the same way backwards as forwards; LINCtape uses a
different set of markers.


Rich Alderson
Vintage Computing Sr. Systems Engineer
Living Computer Museum
2245 1st Avenue S
Seattle, WA 98134

mailto:RichA at LivingComputerMuseum.org


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