I was just looking at this item on e-bay:
http://cgi.ebay.com/BASIC-UTILITY-ROM-V ... dZViewItem
The description includes this:
"Also, with one instruction and when sufficient memory expansion is present, it formats the VIC to imitate the 8K, 3K or minimum memory configurations."
I have the programs and/or commands that that can take a +3k or 8k+ vic and "unexpand" it.
But how about taking an 8k+ vic and unexpanding it to a vic +3k? Is this possible with a few commands? It sounds like it from the description of this product. Anyone know how?
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Anybody know how they did this?
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Anybody know how they did this?
Last edited by viclizard on Wed Feb 16, 2011 6:45 pm, edited 1 time in total.
3K ram expansion is possible by using /RAM1 /RAM2 & /RAM3 block select lines on expansion port. 8K expansion may be done using /BLK2.
Either cart has decode logic to use 3K of 8K chip or there is a bank of 3K RAM and an 8K chip. Selectively turning these off via software control could be done via I/O2 or I/O3 area and it is pretty simple to do.
Either cart has decode logic to use 3K of 8K chip or there is a bank of 3K RAM and an 8K chip. Selectively turning these off via software control could be done via I/O2 or I/O3 area and it is pretty simple to do.
Mega-Cart: the ultimate cartridge for your Commodore Vic-20
I understand a little of what you are saying. I *think* I understand the first part. But not enough after I get to the "Either cart has decode logic to use 3k of 8k chip or there is a bank of 3k ram and an 8k chip.".
"it is pretty simple to do"
If you would be so kind, would you mind spelling it out for me?
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Last edited by viclizard on Wed Feb 16, 2011 6:46 pm, edited 1 time in total.
A flip-flop such as a 74LS74 could be used to toggle /OE of the RAM. There are 2 flip-flops in a 74LS74 package, so if there are two types of RAM used (one for 3K and one for 8K), then each of these could be controlled independantly on/off or on/off in combination.viclizard wrote:
"it is pretty simple to do"
If you would be so kind, would you mind spelling it out for me?
The possibilites are: uexpanded, 3K expanded, 8K expanded, & 11K expanded.
Some address decode would be adviseable, with preferance to gate with R/W line.
Mega-Cart: the ultimate cartridge for your Commodore Vic-20OK, so if I understand rightly, you are talking about the hardware being different than what is found in a standard 8k ram expander, is that correct?
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Last edited by viclizard on Thu Mar 10, 2011 7:25 pm, edited 1 time in total.
There were at least two versions of the BUTI toolkit. This auction seems to refer to the first one, which AFAIK doesn't come with any expansion memory. The second one, BUTI Plus has +3K built-in, similar to how the Super Expander does I suppose.
That said, if you have a multi cartridge expander, insert this BUTI cartridge into one slot and a regular memory expansion in another slot, I also have difficulties to understand how it could transmogrify a 8K expansion into a 3K expansion, if it requires hardware select lines.
Of course, many switchable expansions have a combination of 3K, 8K, 16K and 24K plus 8K in block 5. I suppose they work like 6502dude describes.
That said, if you have a multi cartridge expander, insert this BUTI cartridge into one slot and a regular memory expansion in another slot, I also have difficulties to understand how it could transmogrify a 8K expansion into a 3K expansion, if it requires hardware select lines.
Of course, many switchable expansions have a combination of 3K, 8K, 16K and 24K plus 8K in block 5. I suppose they work like 6502dude describes.
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