20 Nov 2022 - 4 min read
Well, what a journey that’s been then … I started work on a clock for my relay computer back in May 2020 and today (20th Nov 2022) this post marks the end of it. …
05 Nov 2022 - 3 min read
Quite a while ago I decided to give up on the tedious wire wrap technique for building my cards. Although it was certainly more authentic and in-keeping with my …
05 Jan 2020 - 1 min read
In my last post I covered off the full design for the decoder card so all that remains is to get it soldered up and tested. As before I’ve put a video together which …
21 Dec 2019 - 1 min read
In my last couple of posts I covered off the full design for the controller unit. As the PCBs have now arrived I can get on with soldering up the cards and giving them a test. …
20 Nov 2019 - 2 min read
In my last couple of posts I covered off the full design for the sequencer unit. With PCBs now safely arrived in the post I can get on with soldering up the cards and giving …
04 Mar 2019 - 12 min read
After years of using pad/prototyping boards to build my computer I’ve decided to switch things up a bit and have a go at making a custom PCB. The thinking is that it …
27 Mar 2018 - 4 min read
Auxiliary Control Construction
In my last three posts I covered the design of the auxiliary control unit which will ease entering and inspecting programs in the computer’s memory. With the design ‘in the …
17 Dec 2017 - 2 min read
Incrementer Construction (Part 2 of 2)
In my last post I covered the construction of the lower incrementer card which is effectively a 16-bit half adder. This time I’m going to cover constructing the upper …
10 Dec 2017 - 3 min read
Incrementer Construction (Part 1 of 2)
We’re getting nearer and nearer to a computer that can run though a program in memory rather than just a single instruction … we’ve got memory to hold the …
25 Nov 2017 - 5 min read
Memory Construction (Part 2 of 2)
In my last post I made a start on the memory unit construction with the lower memory card. The lower card centres around the memory IC which runs at 5V. The upper memory card …
19 Nov 2017 - 4 min read
Memory Construction (Part 1 of 2)
It’s time to make a start on the construction of the memory unit and as mentioned in my last post this one is a bit more complex than ‘boring old registers’ …
11 Nov 2017 - 3 min read
In my last couple of posts I’ve been slightly distracted by some ‘miscellany’ but now I return to form and crack on with constructing the program counter. …
05 Nov 2017 - 8 min read
Miscellany Special: Backplane X, Cable Routing and Address Bus
Continuing on with the theme from my last post … here is another ‘miscellany special’ covering all the little ‘side jobs’ I’ve been doing …
29 Oct 2017 - 5 min read
Miscellany Special: Power Distribution
Having somehow forgotten to take time off work I’m now playing ‘annual leave catch up’ which means lots of four day weeks but also, and more importantly for …
06 Aug 2017 - 4 min read
I’ve nearly got the design for the memory cards done and ready to share but once that’s out the way it’ll be time to get on with some construction again. …
11 Apr 2016 - 3 min read
W Backplane Construction & Power Distribution
Before I can test the new decoder, sequencer and controller cards all working together with the rest of the computer I need to construct the ‘W’ backplane which …
29 Mar 2016 - 4 min read
User Interface Construction: Instruction, Clock and Sequencer
Well, the good news is I’ve just passed a major milestone in constructing this relay computer … it can now perform a single instruction in full firing the various …
01 Jan 2016 - 3 min read
Controller Construction: MOV-8, ALU and SETAB
So yea, it’s been a while since my last post … in fact it’s been just over six months. For some reason I decided I didn’t have enough to do in the …
08 Jul 2015 - 6 min read
Sequencer Construction: 8-cycle FSM
I’m just about at the half way mark now for getting the computer to operate the MOV8, ALU and SETAB instructions. The easier cards are out of the way now … time …
07 Jun 2015 - 3 min read
Decoder Construction: MOV-8, ALU & SETAB
In a change from prior form I’m combining the construction and testing of the next card in to a single post this time. Partly because this card is a nice easy one but …
09 May 2015 - 3 min read
Register Construction: Instruction Register
There’s been lots of theory going on in my recent posts but the time for design is over (for now) … it’s time to get constructing. The first card up in this …
04 May 2015 - 5 min read
Those who have been reading my posts and watching my videos (you have my sympathy) will know that alongside constructing this computer I’ve also been busy renovating a …
20 Jul 2014 - 5 min read
User Interface: Display B Initial Design and Construction
In my last post I put together the beginnings of the first display card … named in a brilliant flash of nomenclature as display card A. This time I’m turning my …
12 Jul 2014 - 5 min read
User Interface: Display A Initial Design and Construction
Following on from working on the main data switches in my last post this time I’ve taken the first steps in designing and constructing the first of two display cards …
05 Jul 2014 - 6 min read
Now I’ve got a fully working ALU and four registers completed I want to take a short break from card building and turn my attention to making it easier to interact with …
22 Jun 2014 - 3 min read
Register Construction: A and D 8-bit Registers
I haven’t posted in nearly a month but in between bouts of enjoying the rare British sunshine I’ve been plodding away at the A/D register card and it’s now …
24 May 2014 - 4 min read
Register Construction: B and C 8-bit Registers
As mentioned in my last post I decided this time around not to post after each stage of card construction (being as the construction steps are now pretty similar to those for …
10 Apr 2014 - 5 min read
Enclosure Update: Laser Cutting
I couldn’t resist it any longer … I’ve ordered the laser cut parts for the case doors, sides and bay floor/ceilings. I did say I’d wait for my chosen …
26 Mar 2014 - 3 min read
ALU Construction: Completed Backplane
In my last post I mentioned I’d suffered a bit of a set back with the construction of the ALU backplane. Well, the short version of things is that I’ve admitted …
22 Mar 2014 - 6 min read
Enclosure Initial Construction
I’ve been promising this post for quite a while now … an update on how the enclosure construction is going. Well, it’s very good thanks :) Firstly, …
16 Mar 2014 - 2 min read
ALU Construction: Completed Control Card Full Test
The ALU Control Card is now complete and looks like this: This card was, on the whole, much simpler and quicker to put together than previous cards (despite me initially …
14 Mar 2014 - 1 min read
ALU Construction: Control Card Power Rails & Wire Wrap
I’ve been a bit short of time lately so I’ve been working on the ALU Control Card in little bursts … but after lots of these little bursts I’ve now …
04 Mar 2014 - 2 min read
ALU Construction: Control Card Header Pins & Relay Sockets
Following on from the first two successfully completed ALU cards, for logic and arithmetic, it’s time to make a start on the control card (well, actually, the LEDs and …
23 Feb 2014 - 1 min read
ALU Construction: Completed Arithmetic Card Full Test
The ALU arithmetic card is now complete! The final card looks like this: As I did for the ALU logic card before I’ve put the following YouTube video together which gives …
19 Feb 2014 - 1 min read
ALU Construction: Arithmetic Card Wire Wrap 2
I’ve managed to squeeze in a couple more wire wrapping sessions this week so in this post there’s a few photos of progress so far. Inputs B and C are fully wired …
16 Feb 2014 - 2 min read
ALU Construction: Arithmetic Card Wire Wrap 1
Fear not (just in case you were for some reason) all this talk of Sketchup and enclosures and so on hasn’t totally diverted me from the main task of constructing the …
26 Jan 2014 - 2 min read
ALU Construction: Arithmetic Card Power Rails
Another round of soldering done … this time putting down the power rails on the arithmetic card along with some soldered wire links. This is the last of the soldering …
21 Jan 2014 - 2 min read
ALU Construction: 1-bit Arithmetic Full Construction
So, as mentioned in my last post this time I’ve put in the wire links and wraps needed to test the first bit of the arithmetic card. With these in place I can make sure …
17 Jan 2014 - 2 min read
ALU Construction: Arithmetic Card Relay Sockets
It’s always a fiddly job getting the relay sockets soldered in and the ALU arithmetic card proved no exception. With this in mind I’ve been spreading the work out …
06 Jan 2014 - 2 min read
ALU Construction: Arithmetic Card Header Pins
Following on from the successful construction of the ALU logic card in my last post it’s time to start off the new year with the next ALU card (number 2 of 3 ALU cards …
18 Dec 2013 - 2 min read
ALU Construction: Completed Logic Card Full Test
The ALU logic card is now finally complete! … well, it is now I’ve popped the last few relays into their sockets. The final card looks like this: As the old …
18 Dec 2013 - 1 min read
ALU Construction: Logic Card Wire Wrap 3
I’m now just one session of wire wrapping away from a completed ALU logic card. The final job is to wire up the gating relays that select one of the five logic results …
12 Dec 2013 - 2 min read
ALU Construction: 8-bit Logic Unit Tests
There’s now enough sockets, solder and wires to test all eight bits of the ALU logic card. This isn’t quite a full test as the gating relays that apply one of the …
12 Dec 2013 - 1 min read
ALU Construction: Logic Card Wire Wrap 2
Continuing on with the wire wrapping for the ALU logic card next up is the input and result links: Given the limited range of colours I’ve got to choose from (Black, …
12 Dec 2013 - 1 min read
ALU Construction: Logic Card Wire Wrap 1
Finally, with all the soldering now done, it’s time to set about wire wrapping the ALU logic card. First up is the internal connections within each logic bit: After wire …
10 Dec 2013 - 2 min read
ALU Construction: Logic Card Power Rails
It seems that every time I move on to the next stage of construction on the ALU logic card it’s fiddlier than the stage before it … this stage is no exception. …
10 Dec 2013 - 2 min read
I’ve just realised that as I’ve been constructing the first ALU card I’ve not given much thought to how I’ll actually test the card (or other cards for …
09 Dec 2013 - 2 min read
ALU Construction: Logic Card Relay Sockets
The construction of the ALU logic card is coming along nicely but there’s still a lot of soldering ahead to get all the relay sockets down … and this part is the …
08 Dec 2013 - 1 min read
ALU Construction: Logic Card Header Pins
Following on from the successful construction of the first bit on the ALU logic card in my last post it’s now time to start putting together the other 7 bits and the …
07 Dec 2013 - 2 min read
ALU Construction: 1-bit Logic Full Construction
So, although I probably should construct the logic card methodically a full stage at a time (solder header pins then sockets then wire wrap) I can’t resist fully …
06 Dec 2013 - 1 min read
Following on from my last post I can now test the LEDs that have been soldered and hooked up to the header pins on each of the three ALU cards (Logic, Arithmetic and Control). …
06 Dec 2013 - 1 min read
ALU Construction: Logic Card Wire Links
Before I can test all of the LEDs laid down so far (to make sure they survived the heat of the soldering iron) I need to add some wire links on the logic card between the LED …
05 Dec 2013 - 3 min read
ALU Construction: LED Header Pins
So far, in the construction of the three ALU cards (Logic, Arithmetic and Control) I’ve soldered down the connectors and LEDs. It’s now time to solder in some …
03 Dec 2013 - 4 min read
Backplane Design and Construction
Originally when I was thinking about how I’d connect up the various cards of this computer I had ribbon cables in mind. Ribbon cables are straightforward to use and …
02 Dec 2013 - 4 min read
ALU Construction: Connectors and LEDs
As promised in my last post it’s finally time to get the soldering iron out and make a start on constructing the three cards that make up the ALU. I’m going start …