DMF-32 (and clones) versus DH-11 (and clones) versus DZ/KMC-11

[Henry Spencer]

Opinions you want, opinions you get:

~DMF	+ Dec software supports it.
	+ Trendy.
	- New, so not as well-understood as DHs.
	- Software can thus be expected to have flaws and maybe performance
		problems as well.
	- The hardware manufacturers may not have shaken their DMF lookalikes
		down as well as the DH ones yet.

~DH	+ Well-understood.
	+ Lots of software support with the bugs worked out.
	+ Lots of field experience, hardware likely to work well.
	- Not supported by Dec software very much any more.
	- Old design, could be improved.  (Not clear the DMF represents
		an improvement, though.)

DZ+KMC	+ All Dec hardware, so few maintenance worries.
	+ AT&T likes it.
	+ Programmable, so software interface is (in principle) changeable
		to suit your whims.  In particular, much of the terminal
		driver could be moved into the KMC to offload the main cpu.
		(Don't know how far the AT&T code goes on this.)
	- Fair bit of extra bus traffic, because the KMC has to poll the
		DZs regularly.
	- The KMC is a weird beast and there may be Unibus problems.
	- Programmability is offset by the KMC being horrid to program.

My personal (prejudiced) opinion is that I see no reason to buy anything
but DHs unless you have some sort of special situation.  If you must have
Dec software (e.g. you run VMS part of the time), DMFs are probably the
thing to have.  If you must have all-Dec hardware, Dec DMFs are probably
the thing to buy.  Now that the DMF is available, the DZ+KMC combination
doesn't seem a good buy unless the offloading/programmability issues are
a big win for you.  I don't think any of these devices has a really big
performance advantage over the others.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry