MicroVAX I

[Jerry Weiss]

On 8/14/18 5:40 PM, Josh Dersch via cctalk wrote:
> On 8/14/2018 2:12 PM, Ethan Dicks via cctalk wrote:
>
>> On Sun, Aug 12, 2018 at 11:36 PM, robertbeauchamp33--- via cctalk
>> <cctalk at classiccmp.org> wrote:
>>> My mother is moving and her spouse has a MicroVax I he bought new 
>>> back in 1984 for some crazy amount. I don’t see this model listed in 
>>> your chart? Can you tell me if there is any value to this machine? 
>>> He also has two original monitors.
>> There is some value, since it's in a BA23 and _is_ a VAX, even as slow
>> as can be.  They are somewhat uncommon because they were only
>> available for a couple of years unlike most other DEC machines.
>> Having used one in the mid-80s when they were brand new (and $10,000),
>> they are quite slow and painful and limited to, I think, various
>> versions of MicroVMS and VMS 4.x, depending on disk size (MicroVMS
>> fits on a 30MB disk when the full version would not).  I don't recall
>> if there is any support for them in VMS 5.x - the max RAM is 4MB
>> (unlike later Qbus VAXen, the RAM is _on_ the Qbus) but one could
>> easily put a newer disk controller in there other than the RQDX1 and a
>> larger disk.
>
> Be aware that most (if not all?) QBus SCSI controllers appear to be 
> incompatible with the MicroVAX I.  I'm not entirely sure why this is, 
> but none of the Emulex, CMD, or Dilog controllers I've tried are 
> listed as compatible with the system -- they all state compatibility 
> with the II and later .I've tried using them in my MicroVAX I with no 
> success.  VMS fails to boot, and Ultrix kernel panics.  Not to hijack 
> the thread, but does anyone have any idea why this might be? I'd like 
> to get the system doing something interesting and not having to rely 
> on very old MFM disks would be nice...
>
> - Josh
>
No personal experience here, but the Emulex UC04 is listed as MicroVAX I 
compatible. See 
https://ia801902.us.archive.org/11/items/bitsavers_emulex1987_5921218/1987_catalog_text.pdf 
page 27.

The UC07/UC08 is documented not to support the MicroVax I due to lack of 
Scatter/Gather support.  See 
https://ia801902.us.archive.org/11/items/bitsavers_emulex1987_5921218/1987_catalog_text.pdf 
Section 1.6.3  Page 1-22.

Having no Scatter/Gather (aka Qbus IO Map) is not a surprise as the 
MicroVax I only uses Qbus Memory directly.  Thus mapping to a larger 
physical address space should not be needed  (micronote #22). However, I 
don't follow what changed to lose support on the UC07/08.

Jerry