Re: final cartridge for vic 20

From: Pasi 'Albert' Ojala <>
Date: Thu, 24 Sep 2015 23:28:41 +0300
Message-ID: <>
On 09/24/15 21:48, Anders Carlsson wrote:
> Pasi Ojala wrote:
>> However, if the memory were visible to VIC-I
> Doesn't it take internal modifications to make any sort of memory 
> available to the VIC-I, or can it somehow be achived through the 
> expansion bus?
Yes, and it was one thing xvic had wrong at some point.

There is VR/W signal on the expansion port.

Now, where are the schematics...  Here, but where's the cartridge port..

Only CA0 to CA15 appear in the cartridge port, not VA0 to VA15. 65245 
buffers allow CA (6502 address) to drive VA (VIC-I address) and it is 
strictly one way. The internal RAM is connected to the VA bus. So, VIC-I 
can only access internal memory, not any expansion memory.

> Can the VIC-I read from memory connected to I/O blocks 2 and 3 ($9800 
> - $9FFF if I recall correctly) if that memory is connected from the 
> cartridge?
VIC-I can't provide the address. Another buffer connects CD (6502 data) 
and BD (VIC-I data) buses. This one had direction controlled by CR/W, 
and while CR/W is high during video access, VIC-I can't see the data on 
the CD bus (cart port). Unless you force the CR/W low from the cartridge 

> I believe the VIC-20 scene in latter years has developed a couple more 
> image formats since Pasi's format 15+ years ago, but I believe those 
> are even more CPU intensive with increased FLI like colour resolution.
Time flies... :D


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Received on 2015-09-24 21:00:08

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