[sdiy] OT: COSMAC Elf 2000

[Phillip L. Harbison]

Roy J. Tellason wrote:
> anthony wrote:
> > At first I read the project article avidly, hoping
> > for  a cool project that might consume a lion's share
> > of my vast TTL logic collection.
> 
> Dunno why. [...] It ain't TTL.

Indeed, it is 4000-series CMOS which is not particularly
fast even by 1976 standards. Are 4000 series parts even
available now? I thought they were replaced by the 74HC
and 74HCT series.

> > [...] I could probably make an Altair clone
> 
> Somebody's already doing that,  with a web site and everything,  though I 
> don't have a URL handy at the moment.

You may be thinking of Briel Computers, but their Altair
clone is a clone in appearance only. Inside lurks an ATX
motherboard with a Pentium 4. The only resemblance is the
front panel and I'm not sure it is functional. While the
switches and lights are impressive on an Altair (and even
more impressive on an IMSAI), I would not want to go back
to the days of using them for real work.

> > I have all sorts of 74LS373's and 74LS374's and a few
> > 8088's. I know that the original Altair was based on
> > an 8086, but the switch shouldn't be too hard.
> 
> Nope.  The original Altair 8800 was based on the 8080,
> which is a whole different thing entirely. [...]

While you're technically correct, note that he said he
had an 8088 which is the 8-bit version of the 8086. That
might not be too difficult to adapt to the S-100 bus. I
think the control signals (/RD, /WR, etc.) are mostly
common across both chips. The original S-100 had only
16 address lines whereas the 8088 has 20; however, he
could either put a megabyte on the CPU board or use the
IEEE-696 spec (which added 8 additional address lines).

I guess the remaining question would be... why bother?

> Hey, blinkenlights are cool.  But I haven't figured
> out anything that justifies using a bunch of them yet,
> nor the 7-segment displays I have either.

Neither have I, and this is coming from a guy who has
spent many a man-month using Altair/Imsai/KIM/AIM front
panel switches to enter hexadecimal code, or entering
hand-assembled code into an EPROM programmer. I do not
relish the idea a returning to those days. If your main
goal is to design and build *synthesizer* hardware, I
do not see any reason to return to such primitive tools
no matter how big your pile of 1970's era computer parts
may be.

Actually, I am working on a design that will use 2048
LEDs, but not for a traditional front panel. It will
have one status LED per processor.

With that said, I return to lurk mode. :-)

-- 
Phil Harbison