The smell of solder and progress... and some glue

I've began working on the second board of the computer. Since most of this second board requires the first board I've gone ahead and super glued the two boards together.

Layout

I'm going to describe how my layout is going to work. If you've read my previous entries you'll notice I'm using two breadboard style perfboards. For me this makes wiring easier but there are problems with using them:
1. You need two because one that would be long enough for all the ICs would be ridiculous.
2. It's easier to keep all ICs using the data bus and address bus on the same board. Luckily the only thing that uses the address bus is the ram.
3. There isn't an effective way to put the hex displays on the board directly.

For issue two I put the 1802, the ram, and IC 8 and 9 on the same board. Now any of you who know the schematics well are thinking, "What about IC 4 and 5?" well.... I ran out of room. My first idea was to have them on a separate board with just the hex displays that could be mounted directly to a case but that doesn't work because they are also used in the control logic. So I'm going to have to channel the data bus over to the other board anyway.

I'm making the case out of wood in which I'll mount both boards with long sides touching. The switches and hex displays will be mounted directly to the case.

K-Elf

Found another neat article about the Cosmac Elf. This one talks about using an eeprom on an Elf.

Muller Lab Schematic

I like this schematic better compared to the original. For me it is easier to follow.
Muller Lab Cosmac Elf

It breaks down the original schematic into sections (Basic, Control, Memory, Input, Output, etc)

Adding some features

As those who have read my blog have noticed while I'm not using the typical Cosmac Elf layout I am using a standard circuit. Well I'm thinking of adding some things to the circuit. More specifically adding a series of LEDs (Cause the hex displays are expensive) to show the current address. I need to look into if I need latch or if I can just attach it to the address bus.

Progress after a hiatus.

Sorry for the lack of progress. I got distracted with some of my many hobbies and since I was working on the tedious part of the computer I lost interest. Today I started on the databus and have the first four bits wired to the latch chip. I still have to get the last four bits and then wire all 8 bits to the processor.

Well I've got the address lines done for the ram chips. That was the most time consuming and tedious part of construction. This is board one of possibly three. This is the CPU, Ram, power, and the support chips for the data switches. The second board will contain the control logic for the cpu and the remaining switches. A possible third board will contain the actual switches and output. This may just be embedded into a case I'm not sure yet.

This is a picture of the underside of the board. As you can see (not my sloppy soldering btw) the boards have a solderless breadboard style layout. This makes wiring easier for me and with extra connection spots it gives me the option of expanding the computer.