Building RAM into Veronica – the 6502 computer

ram-for-veronica

It seems strange that RAM is being added to a computer so late in the build, but [Quinn Dunki] must have had it in the back of her mind the whole time because it turns out to be a rather painless experience. For those of you keeping score, this makes her Veronica project Turing complete.

The brightly colored rats nest pictured above connects the new components to the 6502 computer backplane seen in the upper left. [Quinn] decided to go with two 32K SRAM modules which need very little in the way of drive hardware (it’s hanging out on the breadboard to the left). The RAM module will simply listen for its address and react accordingly. There is one hitch regarding a two-phase clock and the need to protect the RAM from erroneous data during the first of those phases.

Getting this all to work actually pointed out a bug in the ROM module she had long ago completed. After picking up on the problem she was able to correct it simply by cutting traces and soldering in jumper wires.

Comments

  1. LordNothing says:

    seems all you need now is a keyboard port. a c compiler would be nice but you seem to know your asm.

  2. MissAndrea says:

    It’s no strange at all. I can remember a time while building and testing my own z80 system on some breadboards…. i was programming, assemblying, burning roms all along…. then a simple program with a subroutine was not going to function at all. Then the lig came on … DOH! no ram=no stack where I was saving the return address ??? – Some things are best learned experimenting !

  3. NewCommentor1283 says:

    i like veronica becuase most homebrew computers are either too professional looking (i could open my computer MYSELF to take a peek) or too kludgy (so many wires that you cant even spot the dang chip in the middle

    i like veronica because it looks clean and “viewable” but at the same time its obviously homemade and not a professional prototype you’d find kicking around the R&D department of some large company

    its the perfect mix.

    PS: the colored ribbon cabling adds such nice color, my desktop doesnt even color pin1 red like they used to

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