11/23 and 11/73 compatibility

On 06/01/2011 10:18, Pontus wrote: Yes, your 11/23 bootstrap is on the BDV11, normally. But the MXV11-A also has a bootstrap. You can disable the bootstrap on either card, so if they were both in the same system, one of them will be disabled. The BDV11 is a bit more versatile in a few ways. You can rejig it by changing wire-wrap links to accommodate different (EP)ROM sizes and mapping arrangements, and thereby use larger bootstraps, albeit spread over several ROMs. It's rather tedious to do this, though; you'll see what I mean if you look at the manual. If you're determined you can even replace a couple of the 24-pin sockets with 28-pin ones and put larger EPROMs on it; I have an 11/23 running with a large bootstrap in 2 28-pin EPROMs. The point of telling you that is that it's one way you could put an 11/73 bootstrap in it. The way the BDV11 mapping hardware works is compatible with the later bootstraps for 11/73 etc. Also, although most BDV11s are 18-bit, that only refers to the bus termination. The I/O functions use BBS7 to decode the I/O page so the cards will work in a 22-bit system and if yours is only 18-bit, ECO M8012-ML005 upgrades the termination to 22-bit and is easy to do. Rev E and later already have that. But see the note below about your BA23 box. As for the MXV11, it's about the same vintage as the BDV11. It was meant as a multifunction card for small systems. Instead of building an 11/03 or 11/23 with CPU, memory, SLU card, and bootstrap/terminator, you can do it all with a CPU and an MXV11 -- two dual cards. It makes a very neat tiny system, and at least a couple of us on the list have systems like that, but it only supports 18-bit memory addressing. The MXV11-B is a completely different card, and that does have an 11/73-compatible bootstrap (as well as much more memory). Not necessarily, if you're willing to either re-configure or to modify your BDV11. There may be some suitable bootstrap ROM images on certain websites :-) (hint: look at the directories one level above where you found my Q-Bus chassis files) While a quad-height KDJ11-B and some PMI memory would be nicer, still your dual-height CPU, plus SLUs, bootstrap, and memory will give you a reasonable system. The backplane in a BA23 is always an H9278, which has Q22-CD in the top three slots and Q22-Q22 in serpentine arrangement under that. You can use a dual-height or quad-height CPU in the first slot with up to two cards that need CD-interconnect (or most dual- or quad-height QBus cards, so long as they only need QBus on sections A and B) below that, or use a quad-height KDJ11-B CPU in the second or third slot and put PMI memory in the ones above. Your DZV11 may be worth keeping for extra serial lines in this context, but it can't be used for a console SLU -- you need a DLV11 of some variety for that (your DLV11-J, or the MXV11-A with everything but the SLUs disabled). Your BA23 has a backplane with pluggable terminations, so you don't need the BDV11 for bus termination (nor LTC control), only bootstrap. You don't want to have two sets of terminators, but you can remove the terminating resistor packs from either the backplane or the BDV11. -- Pete Peter Turnbull Network Manager University of York