Though I've made some hardware mods, it is functionally equivalent of the original ELF. My mods include:
- Changing the HEX display to binary LED's; way cheaper.
This mod was actually suggested in the original article.
- Changed the two 4 bit 2101 RAM's for eight 1 bit 2102 ones.
I had them lying around and besides the "width" they're very similar. Furthermore, they're 1977 vintage - adds something to the design.
- Sprung for another layout, not wirewrap
Once again, I'm out of wrap wire, and I kinda wanted it to have more of a Altair 8800 / MIPS 8080 kinda look.
Here it is:
The 8 chips with dual round indents are the RAM.
I have redrawn the schematic into a more reader friendly form than the original, spreading it over 6 pages:
1) CPU and clock
2A) Original RAM
2B) My RAM
3) I/O logic
6) CPU control
Makes it much easier to debug and alter.
Anyway, so far, I've wired the processor control and power.
Buses are to come.