osiweb.org

Hi all,
Now that I have my C2 up and running as a disk system, I notice that a lot of the disk (disk images actually as I'm using a Flash Floppy Gotek) that work on my C4, don't run well on the C2. I'm assuming this is may be a speed issue as I believe the C2 is running at 1mhz clock.

So I'm looking at overclocking to 2mhz. I found in some reference at the back of this PDF on the 502:
http://www.osiweb.org/manuals/502.pdf
The article was taken from MICRO magazine. Although it does not say what board is being modified, I'm assuming as it's attached to the 502 schematics doc, that it's pertains to the 502.

The article states "Move the Jumper from bus pin #18 off IC#E4 pin #13, and onto pin #14...Unfortunately I have no idea what IC#E4 is, as all the schematics I've looked at use the 'U#' numbering scheme for IC placements...

Can anyone help me identify where IC #E4 is?
My best guess is that it's U11

Thanks

Can anyone confirm that E4 is indeed U11?

Cheers

This is the first mod I ever did on my C2-4P. The 502 board has no crystal clock, so on systems with a 540 board, the clock signal is taken from pin 18 of the bus, O0 (phase 0 in ), which is driven on the 540 board by a jumper to the timing chain.

On a 540A, the (approximately) 1MHz clock would be E4 pin 13, and the (approximately) 2MHz clock would be E4, pin 14.

If you have a 540B, then the chip is U5D, same pins.

The 505 board has a crystal on board, so no 540 board jumper.

Cheers,

Dave

Ahhhhh...ok, now this all makes sense.

Thank you for the clarity.

Phil