--- healyzh_at_aracnet.com wrote:
> > > I hope you realize that with a MicroVAX II, especially in a BA123,
> > > the most desirable part is the chassis itself...
>
> I figured that might be the case. Which is why I brought it up. The thing
> to remember is that a BA123 from a MicroVAX II makes a *VERY* nice starting
> point towards building your own PDP-11.
Yep. Lots of elbow room. Eventually, I'll get my KDA-50 up and all, but
for now, it's a nice MFM disk farm.
> I'm sure there are lots of people that will disagree, but a MicroVAX II is a
> real dog, I'd rather use it as a parts donor for a PDP-11, and run VMS on a
> 4000 class VAX (either a VAXstation 4000, or a VAX 4000/*) if I'm running it
> on a VAX at all.
I would, too, if I had a 4000-class VAX. OTOH, I have some stuff (like
COMBOARDs) that do not run on 4000-class VAXen because of timeout latency,
etc. I have recently run across a document I received from a DEC engineer
years ago where they describe what devices are not rated for use in a
VAX 4000 because the timeouts had lengthened over the years and over the
various models. I need to scan this in. We first noticed the problem
when a VAX 4000 w/TLZ04 and COMBOARD would lock up so tight that we had to
power off. Turns out the TLZ04 was starving us and the timeout recovery
mechanism that worked with MicroPDPs and uVAX-II and uVAX-III CPUs changed
enough with the VAX 4000 to cause serious wedging.
If all you need is a VAX processor, memory, disk, some flavor of tape,
some serial devices and a network device (DDCMP sync-serial and/or Ethernet),
then a VAX 4000 is a great production and hobby box. If you have certain
devices that you need to use, for data interchange or the like, a VAX 4000
may or may not be the best choice.
> PS I'm not trying to start a flamewar, it's just my opinion, and largly
> based on the fact that MFM disks are the standard for MicroVAX II class
> machines (and yes I've got several that are still VAXen, including a
> VAXstation II/RC that won't be a parts donor (hey, it was my first VAX if
> nothing else)).
I find _that_ to be the biggest limitation of the uVAX-II - I have enough
MFM disks to keep my machines working, but since newer versions of VMS
don't like to fit on an RD54, I'm kinda trapped. I need the older stuff
for some reasons and I'd love to move to newer stuff for others (mostly
modern disks and communications devices).
I have a BA123 that I'm currently setting up as a uVAX-II because that's
my "biggest" Qbus machine. I expect to recycle its BA23 with a KDF11
CPU because that's my biggest Qbus PDP-11. Nobody has thrown a newer
VAX or MicroPDP my way yet (except for the Pro380/Console I rescued from
work when we dumped the VAX 8530 8 years ago).
-ethan
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Received on Wed Jun 13 2001 - 17:05:43 BST