<VS 3100m76 and VAX 4000-300 use the same CPU, but DEC sais the m76 has 7,6V
<the 4000-300 has 8VUPs. Don't know if this is a difference in cache, or a
<difference in I/O. My personal checks (compiling NetBSD kernel) resulted i
<the 4000-300 being slightly slower than the VS 3100m76.

Difference in memory and IO organization. the 4000-300 is definately faster 
if your loading the IO.  At light loads it's hard to tell one from the other 
if they are both running VMS.

<But both are very fine boxes, if you like the QBus, you really should get 
<4000-300. 4000-500 port might take some while, the CPU is a bit difficult.

the BIG advantage of the Qbus boxen is IO extension for serial lines and
all manner of non scsi interfaced things.

Allison