FPGA VAX update, now DIY TTL computers

[Allison]

>
>Subject: Re: FPGA VAX update, now DIY TTL computers
>   From: 9000 VAX <vax9000 at gmail.com>
>   Date: Wed, 09 Nov 2005 00:35:00 -0500
>     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>On 11/8/05, Chuck Guzis <cclist at sydex.com> wrote:
>> On 11/8/2005 at 5:36 PM woodelf wrote:
>>
>> > Well everybody likes 12 bits...
>> >  http://www.cray-cyber.org/hardware/Hardware.php
>> >   Forget TTL, go tubes!
>>
>> Wow, now that's ambitious!
>>
>> Makes me wonder, though.  Around the time the transistor was in its
>> ascendancy, the vacuum-tube business came up with a couple of innovations.
>> One was the nuvistor--an almost transistor-sized tube; and the other was a
>> low-voltage tube used in automobile receivers that were specified for 12.6
>> volts on the plate (e.g. 12AE7 dual triode).  These would be coupled with a
>> solid-state driver and power amplifier for a auto radio with no vibrator
>> supply.
>>
>>  The first would seem to make the scale of a digital computer more
>> attractive; the second would seem to substantially reduce the power
>> requirements.    To anyone's knowledge were either of these two components
>> ever used in digital applications?
>
>It is funny that I am a tube fan too.
>
>The 12.6 volt tubes won't save you any power; On the contrary, they
>sucks much more power than normal tubes. Because they need a lot of
>current to heat the cathode to emit more electrons; and they have a
>positive first grill to 'pull' electrons out from cathode.

Space charge tubes llike 12AD6, 12ek6 for automobile radio service.

I've run common tubes like 6u8 and 12at7 at 12V on the pate with good 
results.

>Nuvistors are not good to use for homebrew computers either, because
>they are expensive. Months ago I saw a board with 10+ nuvistors. I
>didn't buy it ($9.99) because I was not small-tube fan. I checked the
>second hand price at that time and it was significantly higher than
>those sub $1 tubes.

Nuvisters were ceramic metal tubes developed for VHF and UHF recieving.
 They are mostly triode designs though there were tetrodes.  I have a 
reciever I built that uses one for the RF amp and another in an osc.
Small, lower noise but there are glass tubes that are similar.

Allison