DEC RK07 drive interface specs wanted

From: Tom Uban <>
Date: Fri May 14 08:45:01 2004

At 12:41 AM 5/14/2004 -0500, Patrick Finnegan wrote:

>On Thursday 13 May 2004 21:09, Tom Uban wrote:
> > I disagree about MSCP making more sense. If the controller is to be
> > used on older pre-MSCP operating systems, then MSCP will be useless.
><sarchasm>But who'd ever want to run an OLD os on classic
>Seriously, you've got a point, and I hadn't thought about that fact
>before. Part of the issue is that I don't have any of that "old"
>versions of software/OS that won't talk MSCP.

Well, V6 Unix did not have an MSCP driver that I know of. I ported
an RL11 driver to my copy a number of years ago, so it barely had
that. There may have been some more complex drivers for V6 later on.
I would also guess that versions of standard DEC OS and diagnostics
which predated the MSCP exist as well.

>So, what devices would give us the largest range of possibilties for
>software compatibilty at the larges size?

I'm thinking RK11 and RP11.

>If we're to use a microcontroller to run this board, then it'd be
>possible to have "changable firmware", and either change it to emulate
>the type of device you want, or to emulate multiple devices. On second
>thought, you probably don't need a microcontroller for that, but it
>seems easier than going the FPGA/PLD route to do it.

An FPGA would potentially allow for a large number of registers all
in a single package, that could be "re-wired" as necessary after the
design was completed. If discrete logic is used for the registers,
then the design will end up being fixed. A micro-controller would allow
for the management of the disk space independent of the PDP-11.

><reaches for pdp11 peripheral handbooks>
>In 1970 pdp11 handbook:
>- no disks, just a teletype and papertape reader are listed.
>Added in 1973/4 pdp11 peripherals handbook:
>- RK11/RK05 - 2.4MB disk pack
>- RP11/RP03 - 40MB disk pack
>Added in 1975 pdp11 peripherals handbook:
>- RP04 - 100MB (presumably same RP11 interface as RP03)
>Added in 1975 pdp11 peripherals handbook:
>- RL11/RL01 - 5MB disk pack
>Added in 1978/9 pdp11 peripherals handbook:
>- RK06 - RK11, 14MB disk pack
>- RK07 - RK11, 28MB disk pack
>- RM02/03 - RM11 MASSBUS interface, 67MB disk pack
>Added in 1981/2 pdp11 peripherals handbook:
>- RL02 - 10MB disk pack
>- RP06 - 176MB disk pack
>- RP07 - 516MB winchester
>- RM05 - 256MB winchester
>- RM80 - 124MB winchester
>So, it looks like to me the best choices would be an RK11/RK05(06,07),
>an RP11/RP04(05,06,07), an RX11/RX01 and and RL11/RL01(02) emulator.
>If I were to pick a single choice right now, I'd probably pick the RP11
>controller, for the breadth of possible sizes (from 40MB in 1973 to
>516MB in 1981), and put RL11 as a second choice, simply because I've
>got one. :) RK11/RK05 seems too small to be worthwhile, but the RK06
>and RK07 aren't bad sizes.

I'm not sure how much it matters if the emulated controllers match up
with the physical ones that we have or not. An RL11 shouldn't be much
more difficult than an RK11 emulation.

>Now, I haven't looked much into complexity yet, but at first glance
>through register descriptions, RL11 takes the cake on simplicity on
>just 4 registers, RK11 is middle-ground with 7, and RM11&RP11 are the
>most complex, with at least 20 registers.
>So, as a first try, I'd probably go for the RL11 for simplicity and then
>once that was working, try for the RK11 or RM11/RP11 interfaces. These
>all seem a lot simpler than MSCP (UDA50/KDA50) interface emulation, and
>support media that should be "large enough" for most people (1/2GB).
>In fact, the drive in my VAXstation 3200 is only 650MB, and it feels
>big with VMS 5.3 on it.

With an FPGA, it should be fairly easy to start small and work from there.

>For the actually data storage, I think you'll want to use flash or a
>writeable hard drive (perhaps even a 2.5" laptop IDE drive mounted on
>the UNIBUS controller card). It seems novel to have a 8 (emulated
>drive) x 516MB (4GB total) UNIBUS storage card that takes up a single
>SPC slot.
>Hey Tom, have you started at all on your RK11 emulator? Want to compare
>notes on this?

I've started thinking more about it, so if that counts... I've also been
collecting people's comments on the idea over the years. When I get started
in earnest depends on what my schedule ends up looking like this summer.


>Purdue University ITAP/RCS ---
>The Computer Refuge ---
Received on Fri May 14 2004 - 08:45:01 BST

This archive was generated by hypermail 2.3.0 : Fri Oct 10 2014 - 23:37:10 BST