DEC RK11-C Disk Controller - on ebay...or is it?

Ethan Dicks ethan.dicks at
Mon Feb 8 23:37:36 CST 2021

On Mon, Feb 8, 2021 at 10:22 PM Fritz Mueller via cctalk
<cctalk at> wrote:
> Yup, RK11-C, and it seems complete (modulo drive cables and terminators.)  I have
> one debugged and running in my '11/45, so I know it well.

I've had one for years but I haven't tried working on it yet.

> > On Feb 8, 2021, at 3:16 PM, Ethan Dicks via cctalk <cctalk at> wrote:
> > The ribbon cables are a bit out of place... perhaps they were just
> > stuffed into empty slots to keep them from being damaged.
> The cables are actually in the correct slots -- they connect A30 and B30 to the
> pass-through connectors to support plugging in a pair of KM11s from the
> outside of the rack for debug.

Ah... handy.  I don't recall if mine has those or not.  I do have a
replica KM-11 set that I need to construct.  It will definitely come
in handy.

> On nice thing about this controller is that it supports "Read/Write All" mode, which
> lets you read or write the raw bitstream including block headers.  This can be useful
> for disk recovery if you have a corrupted block header, or for reading/writing "foreign"
> disks (within limits).  This is controlled by bit 9 in the CSR, which is unimplemented on
> the later controllers.

Interesting.  Did not know that.  I don't know that I've ever had a
corrupt disk that I needed to read, but it's good to know that feature


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