UniBone: Linux-to-DEC-UNIBUS-bridge, year #1

Jon Elson elson at pico-systems.com
Sat Nov 16 21:28:19 CST 2019

On 11/16/2019 06:56 PM, W2HX via cctalk wrote:
> Is the BBB not fast enough to do Qbus? Meaning, for qbus, would a FPGA be necessary? Or was this just the op's choice among many possible options?
The PRU on the Beagle Bone Black is pair of 200 MHz 32-bit 
microcontrollers which can do all sorts of I/O tasks.
There is a limit on the number of direct I/O lines 
available, however, so that may not be so simple.  I've used 
for 8-bit ports, plus a few control lines, and that all 
worked great.  There is a bit more latency if you need to
use non-direct GPIO pins to the PRU, but they still are 
pretty fast.

The PRU has direct, 5ns access to a limited amount of shared 
memory, but can access the ARM CPU's memory
with some additional delay.  So, I think you could probably 
do a Q-bus, but might have to go through some
contortions to get enough I/O pins and memory for larger 


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