internal memory expansion

[viclizard]

Hey All,
I have purchased and am eagerly awaiting my ultimate expander from Francois.

One thing still nagging me- that 3k block of expansion ram not touched by the expander. I came across this some time ago:

http://www.cling.gu.se/~cl3polof/vic20expansion/

It describes "piggy backing" ram chips inside the vic to perform an expansion.

I probably don't have the expertise required to perform what I'm asking about, but seeing as how I've got a few non-working vics I figure I'd go ahead and ask and then find someone with the skills to do the job if what I am asking is feasable.

Anyway, here's the Question- could I pull some working ram from one motherboard and piggy back it onto chips on another, do a little magic and end up with the extra 3k? (The article linked describes 16k, not 3k). If so, that would be pretty sweet.

Possible?
________

[eslapion]

Hey All,
I have purchased and am eagerly awaiting my ultimate expander from Francois.

One thing still nagging me- that 3k block of expansion ram not touched by the expander. I came across this some time ago:

http://www.cling.gu.se/~cl3polof/vic20expansion/

It describes "piggy backing" ram chips inside the vic to perform an expansion.

I probably don't have the expertise required to perform what I'm asking about, but seeing as how I've got a few non-working vics I figure I'd go ahead and ask and then find someone with the skills to do the job if what I am asking is feasable.

Anyway, here's the Question- could I pull some working ram from one motherboard and piggy back it onto chips on another, do a little magic and end up with the extra 3k? (The article linked describes 16k, not 3k). If so, that would be pretty sweet.

Possible?

I would like to point out here that the original design for the ultimate expander included a 3k expansion. However, it soon struck me that virtually nothing uses it.

It was once believed that the super expander requires it but in fact, any memory expansion will allow the SE to work just fine. SE fully recognises and utilises the 24k of BASIC expansion provided by the ultimate expander.

My first prototype for the ultimate expander included that 3k and I simply never use it. As a matter of fact, I almost always leave it disabled because some games refuse to work well when they detect it.

[viclizard]

"some games refuse to work well when they detect it"

Ahh- I did not know this.

I knew some didn't work with my expansion + my super expander with 3k, but I figured it was because the rom in the super expander occupied the same location as the rom in some cartridge games.

That's a little weird that it's just the ram being present there causing problems. Actually in my incomplete understanding- very weird that empty ram sitting there would bother anything...

Oh well. I suspect, like you, I would hardly ever use it. I seem to want to expand just to "maximize" the vic. But if it messes some games up, I guess I'll leave it blank and unplug my ultimate and plug in my super if I ever come across something that only runs on +3k.

Thanks for the heads up.
________

[carlsson]

Isn't there even two versions of Super Expander, one with and one without the extra 3K?

[eslapion]

That's a little weird that it's just the ram being present there causing problems. Actually in my incomplete understanding- very weird that empty ram sitting there would bother anything...

It is not really the presence alone of RAM that causes problem. Many cartridge games have code in them to actively try to detect the presence of RAM in specific areas and sometimes even try to self modify. This is a form of copy protection.

That's why the ultimate expander, in order to be compatible with all cartridge games, has to incorporate a read-write/read-only switch.

[Jeff-20]

Isn't there even two versions of Super Expander, one with and one without the extra 3K?

I've never heard of this. If one without memory exists, it would seem impractical. The extra memory is needed to pull off the extra functions.

[carlsson]

I thought that was the difference between VIC-1211 and VIC-1211A, but obviously not.

For practical purposes, it is possible to load the Super Expander ROM dump into block 5 without other expansion memory. You get 3445 bytes free at the Basic prompt. Commands such as RJOY, KEY, SCNCLR and sound commands (including those in PRINT strings) work without any expansion memory. Maybe not very useful.

However, it is true that you will get ?OUT OF MEMORY if you try to access the graphic modes. With +3K, SE moves RAMTOP to 4096 but otherwise leaves pointers untouched. With +8K or more, it moves start of Basic to 8192, copies and relinks current Basic program. In both cases, the video matrix for the hires screen starts at 7680, but with +8K memory, GRAPHIC 0 restores the default value to 4096.

[eslapion]

The original post was about putting memory expansion internally in the VIC-20.

I revive this because I think a suggested manner of internally expanding the VIC proposed in issue 20 of Commodore Hacking is quite original.

See: http://www.ffd2.com/fridge/chacking/c=hacking20.txt

You can use 6264 or 62256 memory chips.

I suppose you could use these plans to add up to 32k of RAM internally.