VIC-20 Tactile 6mm

Commodore VIC-20 Hardware Projects

Hardware & information for the VIC-20.

MFJ-1258 Capacitance Meter

By MFJ Enterprises

HAMSOFT Cartridge

By Kantronics

VIKTRAK+ Software & AUTOTRAK Cartridge

By K7NH/Neil Hill

6560/6561 A/V Breakout Board - UNTESTED

The VIC's default video output is pretty bad. I've long wanted to "go back to basics" and see how the output can be improved by, for example, wiring it up as per its original datasheet example circuit.

The first step is to create this breakout board to isolate the A/V signals from the video output stage on the VIC's motherboard.

I hope that it will allow me to see what signals the 6560 outputs natively, then start to build on that.

BTW, yes I know there are boards out there that already do this. I've not had much luck with the free or paid-for boards, so I want to ... TRY TO ... understand it myself. Let's see ...

6502 to W65C02S Daughterboard - UNTESTED

Unlike the 6522 VIAs that can be directly swapped for modern CMOS 65C22s from WDC, the W65C02S can't be directly swapped - a daughterboard is required to buffer the data bus signals and also handle some other signals/pins that differ.

Serial Port Breakout Board for Logic Analysers

I'm curious how JiffyDOS does its thing so whipped up a simple breakout board for the serial port so I can quickly and very easily connect up my logic analyser to capture the signalling with & without JiffyDOS.

Connect the board to the VIC & the disc drive with a DIN-6, and then a 2x4 Dupont-style cable for the logic analyser.

RAM Expansions

Okay, my mind is full of ideas so it's probably a bit confusing with all these different designs.

My original intent/idea was to replace the orignal ten 2114 RAM chips in case they were faulty. It then grew from there.

The different designs are:

• Original 8KB (BLK0) expansion: Replace the original 5KB plus 3KB expansion, switchable on/off via external switch. This used a PLD which, in hindsight, is more complication than really needed.
• New 8KB expansion: Replace the PLD with the 74LS138, replicating the original VIC design but intercepting the ~RAM1/2/3 select signals.
• Simpler 8KB expansion: For a full BLK0 we really only need the ~BLK0 select signal so this greatly simplifies design but isn't switchable on/off.
• Full 32KB (BLK0/1/2/3) expansion
• Really Full 40KB (BLK0/1/2/3/5) expansion: Two designs to give the full 32+3KB expansion. The Rev. A uses SMD and a larger SRAM and is, IMHO, overly complicated. The Rev. B design is through-hole and piggybacks an 8KB (6264) SRAM on-top of the 32KB (62256) so we don't need to widen the board.

Orignal Internal 8KB RAM Expansion - TESTED

My attempt to replace the VIC's built in 5KB of RAM (ten 2114 chips) with a single 8KB chip, with an extra 3KB RAM as a free bonus.

New Internal 8KB RAM Expansion - DESIGN

Removes the PLD and re-uses the 74LS138.

Simpler Internal 8KB RAM Expansion - DESIGN

Just the 8KB for BLK0, nothing else. As simple as my simple mind can make it.

Internal 40KB RAM Expansion - DESIGNED

I've obsoleted the 32KB design and gone for this: the full 32KB of RAM in BLK0/1/2/3 plus an addition 8KB RAM or ROM in BLK5.

The BLK1/2/3/5 are switchable off externally for software compatibility, and the BLK5 can be filled with either a 6264 SRAM or 2764/2864 (E)EPROM. There is a header to switch whether it is writable (RAM) or not (ROM).