[TUHS] Upgrading from 11/40 to 11/45 in Unix v6

Will Senn will.senn at gmail.com
Mon Dec 31 12:25:07 AEST 2018

Dear Unix Enthusiasts,

We are seriously considering upgrading our PDP 11/40 clone (SIMH), to a PDP 11/45 (preferably another SIMH) for our Unix v6 installation. Our CEO was traveling and met a techie in first class (seriously, first class?) who told him that we needed one. I thought I had better ask some folks who have gone before about it before we jumped on the bandwagon. By way of background, Our install is pretty small with a few rk’s and 256K of ram along with a few standard peripherals, and some stuff our oldtimers refuse to part with (papertape, card punch, etc). It has fairly low utilization - a developer logs in and writes code every few days and the oldtimers hunt the wumpus and play this weird Brit game about cows. It could be considered a casual development and test environment and an occasional gaming console.

Here is what I would like to know that I think y’all might be particularly equipped to answer:

1. Are there any v6 specific concerns about upgrading?

2. Why should we consider taking the leap to the 11/45? Everything seems to work fine now.

3. If we jump in and do the upgrade, how can we immediately recognize what has changed in the environment? I.e what are some things that we can now do that we couldn’t do before?

4. If we just insert our current diskpacks into the new system, will it just boot and work? Or what do we need to before/after booting to prepare/respond to the new system?

5. Is 256K enough memory or what configuration do y’all recommend?

6. Is there anything else we need to know about?



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