[Info-vax] Why it is a good idea that OpenVMS isn't on x86-64 just yet

[Johnny Billquist]

On 2016-01-15 23:27, terry-groups at glaver.org wrote:

> Probably the most complete hardware snapshotting (I don't know about the 9000-series, from the same development group) was the VAX 8600 (and later the 8650). The "console media" was expanded from the floppy / TU58 of earlier VAXen to an RL02. In addition to the normal things on the console media, there was room for 2 (IIRC) hardware snapshots. My memory (which, unfortunately, lacks ECC) tells me that each MCA (the logic chips with the "double decker hat" heatsinks) had an accompanying SIP module which collected the relevant logic states and shipped them serially to the console processor.

Part of the reason is exactly the development group. Both of these (the 
8600 and 9000) from the the large systems group. They had a slightly 
different philosophy than those making smaller machines...

If you want to, I can give you some sample snapshots to post, since I 
actually still have an 8650 running... Boots both VMS, Ultrix and NetBSD...

> In addition to finding design issues, this eventually became useful for locating hardware faults - once enough data about "if X fault happens, replacing the Y board fixes it Z percent of the time" was collected, DEC could interpret the snapshot, rather than just replacing boards one-at-a-time.

Yes, the diagnostics and troubleshooting are very extensive. Also, most 
stuff is redundant, so if something breaks, the system don't crash. You 
just get notified that at the next PM, you should replace some broken 
hardware...

> I don't know if the logic snapshot facility was part of the original design or a later add-on. Certainly the 8600 had a troubled enough gestation that it was a useful feature for the designers. I believe the 8650 provided the originally-planned 8600 performance. If the rest of the system was up-to-rev, it was a simple 2-board swap to upgrade 8600 -> 8650.

It was there originally. And can only remember one board that needs to 
be replaced, but it might be two. I can check if needed. There are also 
some microcode differences. But the clock generator board is the one I 
know is replaced.
You can actually tell what frequency the machine should run at, at the 
console. But the the 8650, the "normal" speed is 72 MHz. I think the 
8600 is at 40 MHz. But during testing, the machine is run at both a bit 
higher and lower frequencies.

The 86x0 machines are just so much fun. The most enjoyable VAXen I've 
played with. But admittedly, I never touched a 9000...

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol