Hi Jerome, thanks for the info! According to the Microcomputer Interfaces Handbook, my H9273 backplane should be all ABCD. Am I correct in that I shouldn't have any problem using the RLV11 in that backplane?
On Wed, Oct 28, 2015 at 11:29 AM, Jerome H. Fine <jhfined...@compsys.to> wrote: >>Noel Chiappa wrote: > >> > From: Ben Sinclair >> >> > I'm trying to get my RLV11 working >> >> Oh, I was going to mention this about the RLV11 - it's a Q18 device. So it >> _probably_ won't work in a system with more than 256KB of memory (which >> you >> don't, at this point, have, though). It would all depend on the OS, >> whether >> it understood that it couldn't DMA to anywhere above 256KB. (The >> controller >> should work OK in a Q22 system - it just won't drive the high address >> lines, >> so they will go to 0 - but it just won't be able to DMA to high memory.) >> > The rest of Noel's reply agrees with my information, so > I will not comment. > > However, just to place another option on the table, here > is that option which I observed around 20 years ago. > > I was looking at some PDP-11 hardware in a BA23 box > and I noticed it had an RLV11 in slots 2 and 3. For those > of you who don't know the details, the first 3 slots are > ABCD and the other 5 slots are ABAB. Of course, all > of the slots in a BA23 box are Q22. > > The key point is that an RLV11 MUST be placed into > a pair of ABCD slots, probably adjacent. Since the > CPU board in this example was in slot 1 in the BA23 > box, there were only 2 ABCD slots available in any > case. NOTE that placing an RLV11 in two ABAB > slots will probably ALWAYS result in a release of the > magic smoke which activates all computer boards (at > least it did when I performed the experiment). > > One key point to understand is that although the RLV11 > can't perform DMA to memory above 256 KB, that > does not mean that the system can't have more than > 256 KB of physical memory. > > If there is anything that I have omitted by way of a > full explanation, please ask. > > Jerome Fine -- Ben Sinclair b...@bensinclair.com