[Info-vax] RB730 Integrated Disk Controller (R80/RL02) usable with VAX-11/750?

[Bob Koehler]

In article <ips1gq$7i2$1 at Iltempo.Update.UU.SE>, Johnny Billquist <bqt at softjar.se> writes:
> On 2011-05-04 06:32, Bob Koehler wrote:
>> In article<ipqpfi$qvl$1 at Iltempo.Update.UU.SE>, Johnny Billquist<bqt at softjar.se>  writes:
>>>
>>> Except then of course it isn't the system bus, but just an I/O bus... :-)
>>
>>     If everything except the CPU-memory connection is on the same
>>     bus, and CPU and memory are also on that bus, then which is the
>>     system bus?
> 
> Uh? The memory is not on that bus, or even near it. I thought we had 
> just established that.

   If the memory was not on the UNIBUS, then I/O peripherals could not
   do DMA.  There might have been some PDP somewhere that I haven't
   looked at that couldn't do DMA, but all VAXen certainly can.