building my own relay computer

Cory Heisterkamp coryheisterkamp at
Fri Feb 13 19:02:13 CST 2015

Tom, any reason for choosing the Harvard architecture?

I'm currently in the middle of a relay computer build so I'll toss in my 2 cents. The most important thing I hit on early is to define the instruction set, work out a number of potential applications/uses on paper (or excel), and step through each instruction to make sure the machine is capable enough. You'll probably discover a number of efficiency improvements you can make to the hardware while doing so, and a few "hardware subroutines" worth adding. You can also baseline how long a program will take to run if you settle on a clock rate, and determine if there's a better way to do it.  

Ultimately, relay computers are SLOW. Don't take 6 cycles to do what could be accomplished with a couple extra relays and a single pulse. Well thought out HW and instructions will pay big dividends when the soldering iron comes out. -Cory

On Feb 13, 2015, at 5:52 PM, Brent Hilpert wrote:

> On 2015-Feb-13, at 2:56 PM, Tom Sparks wrote:
>> On 14/02/15 08:20, Brent Hilpert wrote:
>>> On 2015-Feb-13, at 1:40 PM, Tom Sparks wrote:
>>>> I've been bouncing around the idea of building my own relay computer
>>>> * I have mostly inspired by the TIM project[1] and Harry Porter's Relay
>>>> Computer[2]
>>>> * I am looking at having a limited number registers like the 6502 or 6800
>>>> * the computer is going to be Harvard architecture based
>>>> I wondering have any of use done anything like this?
>>>> [1]
>>>> [2]
>>> I've examined and written about (and done some limited implementation of) Simon, which is Harvard architecture.
>> that website looks familiar, thats it, the memory core write up
>> bookmarked and added to my wget queue :)
>>> Due to it's limitations I haven't been all that enthused about fully constructing it however.
>>> It could perhaps be expanded into something more interesting.
>>> There's another relay computer design and implementation here which looks interesting:
>> I did bookmark and download electronixandmore website

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