#kenbak-1

[commodorez]

Early Microcomputers - Ryan Schiff, Brian Boellner

VCF East XX

[dinosaurspen]

John Blackenbaker and his Kenbak-1 computer. Created in 1973, the Kenbak-1 has been called the first personal computer.

[commodorez]

Here, have a program for the Kenbak-1:

003 set starting address 004 initial value of P register 123 add constant to register B 001 constant=1 351 rotate B left 134 store B to... 200 to the output register (front panel LEDs) 003 add constant to register A 001 constant=1 043 jump direct on A ? if nonzero to... 011 address 011 344 jump unconditionally 006 to location 006

I was playing with my µKenbak-1 after the local vintage computing meetup because I wanted to run something other than the little counting demo from the manual. So I modified what was provided, and learned a bit of the instruction set until I could make it do something different. It's a cool design, once you wrap your head around it.

[commodorez]

Kenbak-1 Series 2 (replica of the original Kenbak-1 from 1972)

Large Scale Systems Museum (LSSM) - mact.io - Pittsburgh, PA

[commodorez]

Some folks are wondering why I’m going to all this trouble designing front panel logic this complicated.  The reason is that I want it to be easy to understand and use, minimizing the number of switch presses wherever possible.

Look at all these front panels and note the variety in designs.  You’ll note that many have locking toggle switches, making you have to switch them all back to zero every time you move to the next entry.  You’ll also note that only a few have switches for both address and data -- a handful do double duty.  Some don’t let you access specific addresses, and instead give you an auto-increment feature to facilitate data entry. 

I ask: why not have both?  Why not be able to hop to a specific address and then increment from there?  Some of these also have push button data entry, but usually that means you have to clear out the entire byte and start over.  I’m adding momentary toggles, but letting you modify the byte you’re currently working on just a bit or two at a time to make life easier. 

You’ll note how many have massive switch paddles to make it easier on your fingers.

Do you have a favorite front panel design?

[commodorez]

(via https://www.youtube.com/watch?v=PDCKNDitH38)

Behold something amazing: John Blankenbaker (with help from Corey Cohen) diagnosing what’s wrong with an authentic Kenbak-1 computer from 1971.  This was done before John’s keynote at Vintage Computer Festival East XI to determine the viability of a demonstration.

[commodorez]

Today I got to behold John Blankenbaker toggling stuff in on a real, mostly working Kenbak-1 computer from 1971! I even shook his hand and thanked him afterwards. According to John, that Kenbak-1 just needs some replacement switches and it will be at 100%. It's not every day you get to meet the man who built the first electronic, commercially available personal computer!

[68kmentat]

Kenbak Corp’s Kenbak-1, considered by some to be the world’s first personal computer!. Invented before the microprocessor, it doesn’t include one!