TRS-80 Model 1 (was: Arty computers (was: Re: PDP-11/70 in Yates Center, KS)

William Donzelli wdonzelli at
Fri Feb 2 14:27:36 CST 2007

> I used the 7070 because that was all that was available.  Don't know the
> 7090.  But at the time the 7070 was the best available.  The US gov paid
> dearly for it even though it had only 9K of memory, 10 bit words and no hard
> drives, just a bank of big Ampex tape drives.

For the record, the 7070 was a solid state machine, as were all the
7000 series processors. Perhaps you were using an older 700 series
machine? They were tube based.

>  When it shut down it took 2
> days to get all the blown tubes replaced so it was back up again.

During the first six months or so, yes, probably, but if tubes kept
going bad like this past this point, something was seriously wrong
with the machine.

Once a tube machine was installed and all the weak tubes weeded out -
generally it took about six months - reliability shot straight up.
Often a tube machine was scrapped with many of the tubes original to
the installation. Remember, these were well made tubes, low power, and
not pushed to their limits.


More information about the cctech mailing list