<-the MicroVAX I's CPU consists of a custom uP and some other components,
< and that together is the uV I. CPU. I think the FP instructions were
< all implemented in microcode.

The cpu was spread across 3 custom chips plus two boards full of logic
and FP was emulated in software with microcode assist.

<-TU81 (and in fact all "big tapes"): I think the TU81 had an own
< interface card that spoke TMSCP with the CPU. Capacity is hard
< to tell, it depends on the writing density, the length of the
< tape :) These were 9-track tape drives, the TU80 could do 1600 bpi,
< I don't know what a TU79/80/81+ could do...

6250bpi GCR is common on the later drives.

<-I think the TU58 should be mentioned, while it was not so much a storag
< device in a sense we say it today, but it was important console media
< for many systems. It was a 800bpi tape that contained 256 KB on a 
< small casette tape (called DecTape II). Average access time was 9.3 sec

It was available as general purpose block replaceable storage just like 
rx02, RX50 or other tapes. It's density was unimportant as the tape format 
was DEC unique and the drive/controller did not have formatting 
capability.  Also it could carry two drives at 256kb each.  It's problem 
that turned off most users was the 30 second end to end seek time.  I 
still have three drive that I use here, their rs423 serial interface 
makes them handy even though slow(yes they even work off of vs2k, 3100s
and MVIIs).

Allison