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 [ 6 posts ] 
 Some bit-serial machines (and projects) 
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Joined: Wed Jan 09, 2013 6:54 pm
Posts: 1690
We've previously mentioned some serial machines in discussions, and MichaelM has at least one in-progress project.

So I thought it might be useful to have a thread to link to those discussions and to talk about bit-serial machines.

MichaelM's MiniCPU-S in HDL and in C (mentioned here too.)
The LGP-30 from 1956 - just 15 flipflops
Olivetti Programma 101 - delay line memory, pretty likely to be a bit-serial machine. Many calculators are nibble-serial.
Early machines mentioned in "Faster than thought" by B. V. Bowden
Ferranti's 12 bit wonder: the 1968 FM1200

Fri Mar 15, 2019 10:48 pm

Joined: Wed Apr 24, 2013 9:40 pm
Posts: 210
Location: Huntsville, AL
Don’t leave out the Elliot Brothers computers. The Elliot 152 is discussed on the forum here.

Michael A.

Fri Mar 15, 2019 11:38 pm

Joined: Tue Dec 11, 2012 8:03 am
Posts: 285
Location: California
The HP-41 calculator/computer which came out in 1979 and was discontinued 11 years later has a bit-serial data bus even though its Nut processor has lots of 56-bit registers and RAM consists in 56-bit registers too.

_________________ lots of 6502 resources

Sat Mar 16, 2019 5:31 am WWW

Joined: Wed Jan 09, 2013 6:54 pm
Posts: 1690
Thanks, both! I'd forgotten the Elliott post entirely. It turns out bit-serial ROMs go back to the HP-35 at least:
although I think the CPU is nibble-serial inside. I could be wrong.

Sat Mar 16, 2019 8:18 am

Joined: Mon Mar 18, 2019 10:34 am
Posts: 1
Does it even matter if the CPU is nubble-serial or not in this case?

Tue Mar 19, 2019 2:42 pm

Joined: Wed Jan 09, 2013 6:54 pm
Posts: 1690
(Welcome, Hullins!)

No, it doesn't matter in a deep sense, but a bit-serial memory is saving pins, in this technology, whereas a bit-serial ALU would also save transistors. A nibble-serial CPU is a good choice for a decimal machine: it's progressively harder to do decimal arithmetic as a CPU gets wider.

(I'm interested to know whether "operating in a serial-parallel mode" was an unambiguous and well-recognised phrase back in the day. There was a time when memory had to be serial, and the CPU probably was too. Then there was a time when parallel (core) memory made sense, but flip-flops were expensive so a bit-serial CPU made sense.)

Tue Mar 19, 2019 3:22 pm
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