[Simh] VAX-3900 only autoboots if you have >64Mb??

[Bob Armstrong]

  This sequence of simh-vax commands auto boots (as it should)

	load -r ka655x.bin
	set cpu 128m
	... extraneous stuff deleted ...
	dep -b BDR 0
	boot cpu

but this doesn't -

	load -r ka655x.bin
	set cpu 48m
	... the same extraneous stuff deleted ...
	dep -b BDR 0
	boot cpu

You don't get any errors, but instead of auto booting the MicroVAX firmware
just stops at the >>> prompt.

  It looks like the BDR setting only works if the CPU is "extended" with
more than 64Mb of memory.  That doesn't seem right - certainly a real
MicroVAX would be able to auto boot under these circumstances.  Am I doing
something wrong, or is this a bug?

Thanks,
Bob Armstrong