Re: VIC-20 Cartridge mapping question

From: Ojala Pasi 'Albert' (
Date: 2000-10-02 16:31:19

> My question is how this is possible? Is the cartridge ROM designed this
> way, or is it VIC which maps a cartridge which doesn't fill a full 8K
> block with itself again?

The ROM is addressed with the address lines and the block select line.
Because the ROM is smaller than the available addresses would allow,
one of the address lines are not connected into the ROM. Because the
ROM is still activated for the whole area, only the lower address lines
matter to the ROM. This is exactly the same as for all ROM/RAM/IO images --
it's simply because of incomplete memory decoding.

"I told you before: Where I go, he goes. And where he goes, I go."
	-- Londo in Babylon 5:"And All My Dreams, Torn Asunder"
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