Next project: 11/24. Does it need memory?

My _guess_ is probably, since on other KDF11 CPU's, ODT works with no memory, but I haven't confirmed that. My PDP-11/24 chassis (a 5-1/4" BA11-L, like yours) I took apart to get the backplane out, so I could work out how the busses work (see below), and I'd need to put it back together before I could try my -12/24.to confirm it. If you could take some pictures of the insides of your BA11-L, that would be both a help to the re-assemblhy, and ancentive to do so. Yes and no. See: https://gunkies.org/wiki/PDP-11/24 for more. Note "The top 256 Kbytes of the CPU's address space were devoted to the UNIBUS". So an MS11-L or similar UNIBUS memory can probably be read/written by the CPU, but it won't appear at 0 in the CPU's address space. Whether a KDF11-U will work with no memory at physical 0 is unknown: it would need at least a special bootstrap (since most assume working memory at 0) and a special OS load (ditto). Also, I seem to recall that on the -11/45, with mapping enabled, interrupt vectors are in Kernel D space, so once running, that machine could operate with no working memory at physical 0, but I don't know if KDF11 CPU's use mapped Kernel space for vectors. If you're interested, I can run an test on a KDF11-A and see. Noel