24 Feb
2006
24 Feb
'06
11:51 a.m.
Don North wrote:
The only problem with SPC slots is they are 18b UNIBUS only. This will
work on 256KB 18b machines, but is a sticky problem on 4MB 22b machines,
since you need to go thru the UNIBUS map to get to all of memory.
For an 11/44, you could do just a dual slot card that goes in a memory
slot (which has 22b address available) and an SPC slot (to get the DMA
lines) but this would be a hex card. To read/write memory, you would
need to be a 22b DMA device, which I'm not sure the 11/44 can handle
(ie, the CPU may always drive the upper 4 address lines and not provide
for 22b DMA device). It may work, it may not. Certainly not what DEC
designed for.
You scared me there for a second. There are no 22 bit unibus dma
devices, right? only 18 address bits on unibus, right? even on an
11/44, right?
[sorry I'm behind - I was out of town]
-brad