On 03/05/2012 04:48 PM, Ethan Dicks wrote:
On Mon, Mar 5, 2012 at 4:15 PM, allison<ajp166 at
verizon.net> wrote:
Ethan
Dicks wrote about the COSMAC Elf:
It's certainly true that the 4016 and 4066 have differences in their
characteristics. However, in the simple way in which it is used in the Elf,
I can't see how it would make any difference. I can't say that I've
actually tried it, though.
I have no difference.
I was told by the engineer
who made the Quest SuperElf that he had a
problem subbing 4066s for 4016s. He was rather insistent there was a
problem. I have not tried it myself, either. My breadboard Elf and
my Quest Elf have 4016 switches.
That may be the super elf. There is one oddity of the 1802, if run at
higher speeds
the timing of the control signals tend to skew badly. Also like all
CMOS voltages
at the pins are critical. I found the 4066 to be better, it's the same
as the 4016
but the series resistance of each switch is lower and the rate is can switch
on or off is a bit faster. I've used both with no issue but I'm fussy
about the
timing and clock rates.
Like any CMOS system get the ground and power well bussed and clean.
It's tolerant but some parts can throw spikes when they switch that are
nasty.
that and also
making sure all the wires go where they are supposed to.
Indeed. That was my
problem on my Popular Electronics Elf.
Wire wrap has always looked like a bowl of pasta to me. Even my own work.
I've built
many of the COSMAC ELFs over the years and still have my wire
wrapped original, a
QUEST PCB version and a few more wire wrapped variants. I made a version of
the ELF on S100.
Nice.
It's one of those CPUs that can be almost called an attractive nusance. ;)
One thing I've not done yet is build a software compatible TTL or CMOS SSI
version of the 1802 from the ground up. I think a 4 2901s could do th bulk
of the registers and D nicely.
I also have
the EELF and ELF2000. It was a simple and very non-critical
CPU to build up and make work.
Yep. I've built those, too. I just pulled out
my Elf2K this weekend.
I need to re-do the switch plate label - somehow a drop of oil got
onto the paper and left a stain.
I like my EELF as it's the whole stack with 8x24 video board. It ended
up in
an old Atlantic Research RS232 line monitor box with a nice 5" monitor. So
the whole result with a PS2 keyboard is very portable though for AC power
only. I need to build a power supply so it can run on a 12V source as there
is room for 7AH battery inside..
Of all the
1802 is the most interesting as it's
not unlike the PDP-8 in that its
simple to the extreme yet still useful.
Agreed.
There's one thing I can do on my Elf2000 that I still can't do on a
PDP-8... play Zork.
But consider this it was lunar lander and a few other games on PDP8
( or PDP12) that got the games thing going. Having played lunar lander
with analog inputs on a vector monitor, I can say it's fun.
Allison