25 May
2005
25 May
'05
7:05 p.m.
From: "Eric Smith" <eric at
brouhaha.com>
I wrote:
Hi
When building neon logic, it might be better to consider
using capacitive coupling to connect up your logic.
Otherwise you may find that you'll have a significant
level shifting problem.
Just a thought
Dwight
You turn on a particular tube by dropping the X
line to 0V and raising
the Y line to +105V. The selected tube sees 105V, while the other tubes
in the same row and column see 97.5V.
Tom wrote:
I think your idea is generally right, but this
detail seems wrong:
when X goes from +7.5V to 0V, the entire line will see 105V,
striking the entire line.
Nope.
7.5V 0V
X0 X1
| |
| |
97.5V Y0 --------90V-----------97.5V
| |
| |
105.0V Y1 --------97.5V----------105V
Locations (0,0), (1,0), and (1,0) are all still below the strike
voltage.
26 May
26 May
2:23 a.m.
New subject: discrete, historic memory, was Re: Neon bulb logic elements link?
On Wed, 25 May 2005, Dwight K. Elvey wrote:
When building neon logic, it might be better to
consider
using capacitive coupling to connect up your logic.
Otherwise you may find that you'll have a significant
level shifting problem.
I think we've reinvented an old wheel that tends towards the
square. Abandoned for good reason!
Slightly changing subject (!), but remaining on discretely
constructed memory, one truly practical memory that was tried and
abandoned about 1952 (one of the Standards computers) was a
switched capacitor memory. It was umm revived some years later and
is now of course universal.
A discrete-capacitor, diode-switched, dynamically-refreshed memory
was built and tested and performed apparently well was built for
SWAC? SEAC? or something in 51, 52 [ref in Huskey's COMPUTER
HANDBOOK] but abandoned as solid-state diodes were prohibitively
expensive.
It would clearly be most straight-forward to build one today, even
with el cheapo ceramic disks. Probably could do .25 sq in per cell
on a PC board. And since one was actually made, it would be
historically correct.
3:55 a.m.
New subject: discrete, historic memory, was Re: Neon bulb logic elements link?
Tom Jennings wrote:
Slightly changing subject (!), but remaining on
discretely
constructed memory, one truly practical memory that was tried and
abandoned about 1952 (one of the Standards computers) was a
switched capacitor memory. It was umm revived some years later and
is now of course universal.
A discrete-capacitor, diode-switched, dynamically-refreshed memory
was built and tested and performed apparently well was built for
SWAC? SEAC? or something in 51, 52 [ref in Huskey's COMPUTER
HANDBOOK] but abandoned as solid-state diodes were prohibitively
expensive.
It would clearly be most straight-forward to build one today, even
with el cheapo ceramic disks. Probably could do .25 sq in per cell
on a PC board. And since one was actually made, it would be
historically correct.
Don't forget discrete-capacitor dynamically-refreshed memory was pioneered by
Atanasoff for the ABC in 1939-41, albeit mechanically accessed (rotating drum, 1500 bits,
max access time 1 second).
One of my languishing projects is a recreation of the ABC prototype (2 registers of 25
bits (capacitors) each on rotating disc, together with serial RVL[1] adder/subtractor.
(Although such a recreation was already done for the Honeywell vs. Sperry-Rand trial in
the 70s).
[1] RVL: Resistor-Vacuum-tube-Logic - the original electronic logic family :)
... recently received a counter using Philips E1T[2] tubes. Not overly useful as a
general-purpose memory but it is a state-holding device (3.3 equivalent bits), and another
example of the bizarre-by-today's-standards techniques from the pre-IC days.
[2] E1T provides similar functionality to dekatrons - one tube providing combined
functionality of decade counter and display - but entirely different technology. The E1T
is based on an electon beam held in 1 of 10 places (states) by a combination of
electrostatic and magnetic fields. The beam can be shifted from place to place with pulses
to accomplish the counting function. Beam then hits a flourescent screen in accordingly
different spots for the 1-of-10 display.
9:32 p.m.
New subject: discrete, historic memory, was Re: Neon bulb logic elements link?
Slightly changing subject (!), but remaining on
discretely
constructed memory, one truly practical memory that was tried and
abandoned about 1952 (one of the Standards computers) was a
switched capacitor memory. It was umm revived some years later and
is now of course universal.
I recall the ABC computer was to use this (or did)?
William Donzelli
aw288 at osfn.org
27 May
27 May
1:27 a.m.
New subject: discrete, historic memory, was Re: Neon bulb logic elements link?
On Thu, 26 May 2005, William Donzelli wrote:
Dynamic RAM is switch-capacitor memory. I have no idea what's
happened in the last five years but I assume data consists of
small amount of electrons stored in an insulator within an address
matrix.
switched
capacitor memory. It was umm revived some years later and
is now of course universal.
I recall the ABC computer was to use this (or did)?
7000
days inactive
7002
days old
4 comments
4 participants
participants (4)
-
aw288＠osfn.org -
dwight.elvey＠amd.com -
hilpert＠cs.ubc.ca -
tomj＠wps.com