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Showing posts from May, 2015

Register Construction: Completed Instruction Register Full Test

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Following on from my last post, and after popping in some relays, the instruction register is complete and looks like this:
As usual I've put a video together that demonstrates this card in operation. In this video I give a quick overview of the card and then demonstrate loading values in to the register and instruction bus. I also  demonstrate gating part of the instruction bus on to the data bus for the I2B (Immediate to Bus) functionality.


That's about all there is to say for this card as it's relatively simple and shares much of its design with the other register cards of the computer. The next card is also a simple one ... the decoder. This will take the value on the instruction bus and decide which instruction class it represents. This card will also be the first where I'll only partially construct it — just enough so that it can handle the SETAB, MOV8 and ALU instruction classes.

Register Construction: Instruction Register

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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 batch is the instruction register and as it shares much of its design with the other register cards the construction is very similar.

The first step is to solder down the LEDs. Here's some pictures, front and back, of the card following this first round of soldering:
I've continued the trend of removing the negative wrapping post behind each LED again to make wiring up easier later on. I've also continued my 'other trend' of hunting for a good way of soldering up the cathodes on the LEDs ... this time I've folded each cathode leg over a piece of trimmed off LED anode leg to create a bridge between several cathodes and then soldered everything down. This seems to be the best way so far and the solder takes to the LED leg better than the using a piece of wire to bridge the cathodes. Unless I come u…

New Workbench

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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 house I bought almost a year ago. This is mostly why there's been a lot of theory and design going on for the relay computer and not much construction ... I haven't actually had anywhere to do the construction ... until now that is.

When I first viewed the house the upstairs back room was just screaming out to be made in to a workshop for my electronics hobby ... although in the end I had to settle for workshop/guest room being as the house isn't solely mine. Anyway, with that back room now fully decorated I was keen to get a workbench of some kind in there. The space I had to work with was as follows:
As you can see it's not the biggest space and to make things even more complicated there's only slightly more than 30cm depth available on the left (the door is just off picture to the left) and 5…