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 octal computing 2022 back to 1959 
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Joined: Wed Jan 09, 2013 6:54 pm
Posts: 1789
There's a link to Goldberg's 27 bits paper in
7 Bits Are Not Enough for 2-Digit Accuracy but it's not a great link, so here's one to the ACM version.


Fri Dec 30, 2022 9:44 am

Joined: Mon Oct 07, 2019 2:41 am
Posts: 619
User programable roms seem to have come out around 1972 as well as most MSI needed for a 4 bit data path.
The 20 bit cpu,looks to be the best design using the memory at the time: 1.5 us core. Floating point is 9 digits binary
with +- 76 exponent. Spring 1973 looks resonable for the ball park FPGA emulation. Concept design is like this PDP11.
Attachment:
45_pdp_11_45.jpg

The 24 bit cpu,may be the best value for the money,as you get a 48 bit floating point number.(11 digits).Note sure if it
will fit in same case as the PDP 11-45.
Memory is still is the biggest cost of the machine.Floating point routines are slowly getting developed, as I have just the I/o to write.
The cross assembler needs to have floating point input routines written.
Ben.


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Mon Jan 09, 2023 5:01 pm

Joined: Sat Feb 02, 2013 9:40 am
Posts: 2104
Location: Canada
24 bits is a nice size. Years ago, after reading about a homebrewed CPU in BYTE magazine, I sketched out a 24-bit CPU on graph paper. It was about 75 to 80 MSI chips, beyond what I could build at the time. I have been tempted several times to create it in an FPGA. It had four address modes, R, [R], [R]+, and –[R].
That PDP case looks good. I had the thought of using plastic shelving for a larger CPU.

_________________
Robert Finch http://www.finitron.ca


Tue Jan 10, 2023 5:24 am WWW

Joined: Mon Oct 07, 2019 2:41 am
Posts: 619
I will stick with 20 bits as that makes a simple hex front panel. I only need to spend a arm and a leg and 3 toes for the PCB.
I need some generic sub mini toggle switch foot prints for ki-cad. Know of any, anybody?
Floating point is now done, but i need now to get some sort of boot strap programming lanquage using
a revised meta II compiler compiler and a cross assembler ( in c) to support high level language constructs
like floating point input, local variables and defines.
Ben.


Tue Jan 17, 2023 8:07 pm
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