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View Full Version : Interesting piece of history of the Mark 8



KC9UDX
April 29th, 2016, 02:01 PM
I see posting an image here is useless, 30926

So here's a link:

http://forums.qrz.com/index.php?goto/post&id=3832343#post-3832343

per
May 4th, 2016, 03:56 AM
Very interesting read.

I recently got into HAM radio, and our club apparently have two 8008-1's in the legacy chip shelf. While the Mark-8 is very early design, and uses certain chips that's difficult to come by nowdays, I was thinking about the posibility to design an 8008 computer using more modern and readily available TTL components.

mwillegal
May 4th, 2016, 06:21 PM
It's been done : http://juliepalooza.8m.com/sl/scel.htm
Or you may consider a true SCELBI reproduction - it's expensive to do, but there really aren't any hard to find parts in the mix:http://www.willegal.net/scelbi/the8008andScelbi.html

Regards,
Mike Willegal
KC1CKV

PS
Byte published an 8008 morse code encoder/decoder program back in the day.


Very interesting read.

I recently got into HAM radio, and our club apparently have two 8008-1's in the legacy chip shelf. While the Mark-8 is very early design, and uses certain chips that's difficult to come by nowdays, I was thinking about the posibility to design an 8008 computer using more modern and readily available TTL components.

per
May 4th, 2016, 07:50 PM
I do notice that many of the early 8008 computers use a whole bunch of dual not gates for propagation delays on the CPU board, while a more recent design; http://www.8008chron.com/ , gets away with only a GAL, some 74LS245/74LS373 (for demuxing/latching the bus) and some flip-flops. The only documented case I have seen where delays have been needed with 80's TTL speed parts and the 8008 is where the /RD and /WR signals gets to the RAM chips too fast.

mwillegal
May 5th, 2016, 11:04 AM
I do notice that many of the early 8008 computers use a whole bunch of dual not gates for propagation delays on the CPU board, while a more recent design; http://www.8008chron.com/ , gets away with only a GAL, some 74LS245/74LS373 (for demuxing/latching the bus) and some flip-flops. The only documented case I have seen where delays have been needed with 80's TTL speed parts and the 8008 is where the /RD and /WR signals gets to the RAM chips too fast.

the interface between the terminal and processor on the Apple 1 contains a 74123 one-shot that adds a few microseconds delay to the circuit.

regards,
Mike Willegal

8008guy
June 14th, 2016, 07:49 PM
I had to chuckle that no one on qrz caught that it was Jon and that the Mark 8 predates everything that they mentioned. It was much of the inspiration for my 8008 design.

Oh well, I guess that there are not many of us that were around back then.

Len (KA7FTP)


I see posting an image here is useless, 30926

So here's a link:

http://forums.qrz.com/index.php?goto/post&id=3832343#post-3832343