Mini 32K RAM expansion hides in your cartridge port.

[k3ys]

Hello all,

I've been working on tricking out my VIC some more. This time I've built a tiny little 32KB RAM expansion that fits inside the cartridge port.

It's based on Adam Bergström's circuit from '95 ftp://www.zimmers.net/pub/cbm/documents ... /32kB.html.

I've added DIP switches to it to select how much RAM is enabled and also there's a whole cart Enable switch and a Read-only switch for helping to run copy-protected cartridge images.

I kept one for myself and have 7 left for sale on eBay: http://www.ebay.com/itm/331602184425

I'll be happy to try and answer any questions you might have about it.

Cheers!

k3ys

[vicist]

This is sooo neat, I bought one

[orion70]

Same from Italy

[k3ys]

Cool! I've shipped them out. Enjoy

[eslapion]

I have used these cypress SRAM chips on a couple of the Ultimate Expanders I have sold in the past and they have an interesting "bug" or "feature".

They have an ultra low power mode so if you plug a 1541 drive left on connected to the serial port, the trickle of current coming back through the reset line when you turn off the VIC is enough to keep the content of the SRAM chip from getting lost.

If you load a cart rom into your 32k expander then turn off your VIC, the cart rom will still boot when you turn back on the VIC.

[k3ys]

That's pretty interesting, eslapion. However, looking over the data sheet it seems that only the LL versions have the 28µw standby. These boards are using the L version of the chip.

I'm still going to try it in the next couple of days and see if I can get it to happen.

[eslapion]

Looking at the datasheet you linked to, the L version has a standby power of about 250-300uW which remains very very little.

I think you'll get the same effect with the L version.

[k3ys]

Well, I can confirm the "feature" exists. I had to haul a 1541 out of storage to test it. I've really have gotten used to my uIEC.

There is a simple workaround for these cases. Either power cycle your drive, OR...

After turning off the VIC, hold down the cartridge's reset button for a few seconds.

[eslapion]

Makes sense since the power comes from the reset line. Short circuit the source and the SRAM chip loses its content...

I didn't even think of this.

[Barney]

If any more become available, please let me know. I am definitely interested in one. Thanks.

[vicist]

Received on 24th July. Had to pay an extra £11.18 GBP ($17.38 USD)(VAT & handling charge)

Tried it out on 27th July. Works a treat.
Many thanks.

[orion70]

Received mine too, same date (I was on a holiday, went to the post office yesterday). Had to pay 10.38 Euros for customs. It's the very first time I have to pay so much for relatively inexpensive stuff. It was a surprise, maybe customs tariffs changed lately. I'll think twice before buying again from the US.
Anyway, I couldn't test it yet.

[Boray]

Nice!

[majikeyric]

it is back!

http://www.ebay.com/itm/NEW-MINI-COMMOD ... 4d35e43e53

[RobertBe]

I just ordered one for myself! When I receive it, I intend to show it at the August FCUG meeting and the September SCCAN meeting.

Didn't come in time for CommVEx this year but for next year...
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm
Southern California Commodore & Amiga Network
http://www.sccaners.org