[HECnet] Qbus ethernet spare?

[Johnny Billquist]

On 2012-06-19 17:13, Paul_Koning at Dell.com wrote:

On Jun 19, 2012, at 10:52 AM, Dave McGuire wrote:

On 06/19/2012 10:27 AM, Johnny Billquist wrote:
Found 1 DELQA and 4 DEQNA (condition unknown), and also have 1 broken
DELQA

I recall that the DELQA is more "modern" and better i some way, are they
also more prone to failure?

No. From a reliability point of view, I've not heard that either should
be better or worse. However, the DEQNA is rather buggy in its general
performance.

  Side-by-side, the DELQA is quite a bit faster than the DEQNA, the
DELQA-YA ("Turbo DELQA") even more so.

  That said, the DELQA has a "DEQNA compatibility mode"...whether that
makes it as slow and/or buggy as the DEQNA, I don't know.

I don't think so.

QNA compatibility mode means it works like a QNA from the driver point of view.   That was never the issue with the QNA -- if it had worked according to the specification, it would have been quite a good device.   The problem was that it never worked correctly, not even after 12 revisions.   Finally when rev L didn't work adequately either, the DEC software teams said enough is enough, we're dumping the QNA.

The issues were most obvious on VMS; I'm not sure if they were visible enough on the PDP11 OSs to cause concern.   Maybe with LAT, probably not or less so with DECnet.   I don't remember the details, other than that Local Area VAXclusters were the ones that tended to run into trouble, since those protocols were particularly unforgiving.

I know that the QNA was not dropped from the PDP-11 OSes, but there are hacks in drivers to work around some issues, such as the receiver (I think it is) that sometimes stops working and needs to be kicked.

The LQA is better, but I've seen issues with that one too.

	Johnny