[cctalk] Re: Need Emulex QD21 help

On Tue, May 26, 2026 at 9:38 PM Jon Elson via cctalk <cctalk(a)classiccmp.org> wrote: So the H9278-A is standard in the BA23 IIRC. Forgive me if I'm going over things you know but that means that the first three slots are Q22/CD slots, so you rightly put the QD21 into the Q22 (AB) side of slot 2. The usual KA630 uVAX II board has 1MB on it, which should be enough to noodle around with, but we always ran those with at least an 8MB board in slot 2 (with the PMI cable). You didn't say what your board configuration is, but might well ask now what _do_ you have stuffed in there? A specific board buildout would be helpful at this point. Normally, it's CPU and memory (essential in the top 3 slots), then peripheral cards in a certain order (low-latency cards over high-latency cards, and unbuffered interfaces over buffered interfaces, and the RQDXn, if any, at the end). For a standard BA23, you don't need to do anything. It's happy with a KDF11-B (11/23+) or KDJ11 (11/53 etc) or a MicroVAX (KA610, KA630). The only trick is where to stuff the CPU and memory when it's PMI memory (above slot 4) (vs Qbus (more flexible). Someone can come along and correct me, but I don't _think_ there's usually anything you have to do with backplane termination when moving from a PDP-11 to a MicroVAX CPU. A basic CPU+memory+QD21 system shouldn't have too many surprises with where the boards go. It's when you want to add items like a DELQA or a KDA50 that have certain requirements. -ethan