[Simh] VAX Tape Emulation?

[Zane Healy]

I’d posted about this nearly a month ago, and have made some real progress this weekend.

Configuration:
MONK
OpenVMS 8.3/Alpha
Compaq XP1000/667

RENNY
OpenVMS 7.3/VAX
SIMH MicroVAX3900

I’m backing MONK up over the Cluster to a “tape drive” on RENNY.

First, Ubuntu includes a package for SIMH V3.8-1.  If you’re just using disk and network, it seems to be just fine.  If you want to write tapes, it seems fine.  If you want to read tapes, upgrade, as it appears to crash OpenVMS V7.3, at least when messing with “tapes" the size I’m creating.  Hopefully the crashing isn’t a clustering issue, I still need to test that.  I downloaded the latest SIMH sources, and built them today, and I appear to be able to read tapes without crashing.  At least it doesn’t crash when reading from the SIMH VAX, I still need to try reading one over the cluster on my Alpha.

My largest backup, from the Alpha, to a virtual “tape”, has been 23.5GB, which resulted in a 27.5GB image file.

Speeds are painful to say the least, but at least I seem to be getting readable backups (I will be doing more testing on that once the current backup completes).

One stupid question, I assume that SIMH emulates the network interface at 10Mbit.  Is there any way to speed that up?  Granted, all my real VAXen are limited to 10Mbit, but a faster link in SIMH would be nice.

Zane