On 10/19/2016 06:48 PM, shadoooo wrote: > > One of my retrocomputing dream is to design an Unibus universal board, > probably based on FPGA because of precise timing requirements, > to emulate one or more disk/tape interfaces, and possibly something more. > The real storage could be based on SD card
You mean, perhaps, something like this? http://pdp10.froghouse.org/qsic/html/overview.html Noel and I started working on this project about a year ago. I've been away all summer, working in the wilds in Alaska, so the project stalled for the last six months. I'm home now and getting back into normal life so it's time to restart. Here's a quick status report on how far we got. Noel wire-wrapped two prototype boards with the bus drivers and level converters. We have those cabled to a ZTEX FPGA module for development. I was working on the Verilog in the FPGA. We got to the point where we had all the basic QBUS bus cycles working: device register reads and writes, bus grant, DMA reads and writes, and interrupt cycles. We hacked up a quick and dirty RK11 using just internal FPGA memory for the "disk" storage and wrote some C code to exercise all those QBUS operations. It seems solid. The short video of the indicator panel on that website above is running that exerciser program. Where we're sitting now is that the next step is to wire up an SD card and start writing the Verilog to access it. It's a little daunting though not as daunting as implementing the USB protocols in the FPGA. I'm hoping that doing the SD card will pave the way for more complex things like USB. Dave
