pete at dunnington.plus.com
Thu Jan 31 05:43:08 CST 2008
On 31/01/2008 03:12, Dave Dunfield wrote:
> At this point, all I'm really looking for is a good "starting point".
> Can anyone recomment a good document/resources for a Q-bus newbie?
There are more descriptive documents, but as a reference to identify
backplanes and related things, you might want to look at
and possibly some of the other files in that directory
One thing that can be confusing is the xx-bit terminology. All the
PDP-11 processors are 16-bit (data-wise) but there are several different
address ranges: 16-bit, limited to 64KB (32KWords); 18-bit, limited to
256KB; and 22-bit, with the full 4MB range. Similarly, some backplanes,
memory cards and bus terminators only support 16 or 18 address lines.
However, I/O devices generally use the I/O page, which is always the top
page in the memory map, and uses a special signal for access regardless
of how many memory lines the system has. The gotcha is that some early
DMA devices only have 18 address lines for accessing the buffers in
> M3106 4-line async
DHV11, needs a breakout cable for the four lines.
> M7555 Winchester and floppy disk controller
That's an RQDX3, so you might want to check the ROM revisions on it. It
is supposed to be used in a chassis that has a built-in board for all
the cable connections to the drives, or with a breakout board such as an
M9058, but you can make your own breakout cable or board (there's a PCB
layout for a board and a document describing the connections on my
website, should you ever need them). I'd guess this one came from your
MicroVAX and probably has fairly up-to-date ROMs.
> M7606 MicroVAX II KA630
> M7608 x2 2/4 MB RAM (boards are fully populated)
These go together. You can't use that MS630 memory on an ordinary QBus
(PDP-11) machine, as it connects to the CPU by the over-the-top connectors.
> M7946 x2 RX01 floppy disk controller
For an RX01 dual 8" floppy, of course, but it can also be used with an
RX02 dual floppy if you set some switches inside the RX02. However, you
can't use it with standard (eg SA800-style) floppy drives.
> M8047 RAM, Async, ROMs
That's an old MXV11-A and probably came with the 11/03. It's not
terribly useful for the 11/23 unless you only use older peripherals, and
it won't work with the MicroVAX.
> M8186 11/23 CPU
That's a basic 11/23 processor, and might be either 18-bit if it's an
early one, or 22-bit otherwise (the common ones are 22-bit). They were
often used as upgrades to older 11/03 systems. The CPU chip is the
40-pin ceramic carrier with two chips on it, furthest from the edge of
the board. If it doesn't have the MMU chip, a plain-looking 40-pin
ceramic chip at the edge of the board, it will only access 64KB. It may
have an optional FPU, which is a 40-pin ceramic carrier with two smaller
chips on it, like the CPU.
> M9400YA 120-ohm terminators with refresh & floppy boot
That's 18-bit only, so will only really be useful with the 11/03, unless
your 11/23 is an early one that's 18-bit, or was only set up as an
> M9400YE Headers and 250 Ohm resistors
That's usually used as a bus extender for a second chassis. Is/was
there another card (M9401) with it?
Pete Peter Turnbull
University of York
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