MEM11 Status Update (Guy Sotomayor)

Michael Thompson michael.99.thompson at
Tue Jan 20 18:42:14 CST 2015

> Date: Mon, 19 Jan 2015 21:27:59 -0800
> From: Guy Sotomayor <ggs at>
> To: cctalk at
> Subject: MEM11 Status Update
> As some of you know I've been working (on and off again) a
> multi-function Unibus board that contains all of the more difficult
> items to allow a PDP-11/20 to run Unix V1 entirely within the CPU
> chassis.  Other than the CPU and the RK11-D controller, everything else
> will be on the MEM11 board.  Here's the background on what the MEM11 is
> and the current progress.
> What's on the board is the following:
>   * Up to 124KW of non-volatile memory
>   * Console Emulator ROM
>   * 4 Boot ROMs selected from 32 images on the board
>   * 2 DL11 SLUs
>   * RF11 controller with non-volatile memory emulating 8 RS11 drives
>   * KE11 EAE
>   * KW11K
>   * KW11L
>   * KW11P
>   * KW11W
> TTFN - Guy
> ******************

I am working on a similar project for the Omnibus. I am connecting a
Microsemi SmartFusion FPGA to the Omnibus, and doing the peripheral
emulation in a combination of the FPGA and Linux running on the ARM
Cortex-M3 hard core in the FPGA. Anything with timing restrictions goes in
the FPGA. Everything else goes in Linux as a combination of a device driver
and an application.

For simplicity, I am starting with programmed I/O devices, with the paper
tape reader/punch first. I should be able to add serial ports, printer
ports, analog I/O, diskettes, card reader, and maybe DECtape. Later I will
add data break (DMA) and add disks and mag tape. I am planning to keep the
disk images in flash, load them into RAM and run from there, and save them
back to flash if the processor is halted.

The MI8E bootloader wiggles the same Omnibus signals as the front panel. I
could have the FPGA do the same, and load any one of a selection of

I am not adding memory, because a nice 32kW RAM board already exists.

Michael Thompson

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