using new technology on old machines. Was: PDP-12 Restoration at the RICM

Johnny Billquist bqt at
Mon Jun 15 04:52:28 CDT 2015

While I agree that as long as things can be restored it's not a real 
problem, I'm surprised that not more people consider it a serious overkill.

We're talking about putting in a rather complex computer to generate a 
baud rate. Are people really that handicapped when it comes to building 
hardware nowadays? Are people aware how easy baud generators are?
We're essentially talking about a clock, which can be found as a 
component (various oscillators), and then dividing it. There used to be 
chips around which did that part, and I would expect it to not be that 
hard to find some if you looked today. Many UARTs even comes with a 
clock divider built in.

And that is it. When I build various Z80 systems, I usually had a Z80 
CTC included, which I used for generating the baud rates.


On 2015-06-15 02:52, Joe Lenox wrote:
> I also think it is in the spirit of the computer - using what is available
> to fix a problem at hand. I think the arduino was overkill when an attiny
> (smaller, easier to hide) would probably serve just as well.
> If you have the ttl logic bits lying around and know how to use them, fine.
> Still would probably need debugging.
> On Jun 14, 2015 2:41 PM, "Simon Claessen" <simski at> wrote:
>> as long as it is done in a way that it can be restored to its original, i
>> have no problems in using newer technology in older machines. we have a
>> alix sbc build into our tek 4002a for demonstrational purpouses, all done
>> without damaging or altering the original machine.
>> On 14-06-15 17:25, tony duell wrote:
>>>   The ripple on the power supplies is still going lower as we put more run
>>>> time on the system. The power supplies are now within spec.
>>> Capacitors reforming naturally?
>>>   Warren made an Arduino based programmable baud rate generator that works
>>>> for both serial ports. After some debugging, it works nicely.
>>> I am sorry, but I find that obscene!. To use more components than the
>>> rest of the machine
>>> (probably) just for the baud rate clock is ridiculous. IMHO if you are
>>> going to modify a
>>> vintage machine, particularly one as rare as a PDP12, you should use the
>>> components
>>> that were available at the time. It's not as if a programmable buad rate
>>> generator is hard
>>> to make from TTL either. In fact given the Arduino thing needed 'some
>>> debugging' it might
>>> well have taken less time to do it in hardware.
>>> -tony
>> --
>> Met vriendelijke Groet,
>> Simon Claessen

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

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