new disks, old DEC (was Re: 4.3BSD Quasijarus)

Brad Parker brad at
Sun Dec 28 19:35:26 CST 2008

Steven M Jones wrote:
>Hey Brad, what about that universal disk controller for UNIBUS you were 
>working on?  (Apologies if 
>I missed an update.)

ugg.  It works, but is currently collecting dust waiting for the economy
to force me into another idle period (which I predict will occur soon).

I programmed it to look like an RL02 and got it to boot rt-11 on my
11/44.  But I didn't like some of the hacks I had to do and so re-did
the cpld and then ran out of space.  Always the way. 

I plan to have another go at it this spring/summer.  I think the idea
has merit.  I think I should have used an fpga instead of a cpld however
but I was being cheap.  It's nice to put the entire bus transaction
engine with dma support inside the cpld.  Originally I had the cpu doing
everything but found it was hard to keep bus timeouts from happening.
The last working version has several state machines which minimize the
cpu work.

It can look like rom and can be a bus master so I use it to goose a copy
of the boot loader into ram which makes life easier.

like everyone, I took on some huge projects over the last 1.5 years and
all my fun work was on hold.  But those days appear to be over for a
while :-| so my back room will be a little warmer.


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