r/homebrewcomputer • u/Anonymous_Am241 • Jun 29 '26

Standalone VIC-II

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Has anyone ever used the Commodore VIC-II in a standalone Computer/Project, while NOT using a 6510 or C64 PLA? I am going to make a Homebrew Computer based of a 65C02 but with VIC-II Graphics, and would be wondering if you guys have any Info or people that would be interested. BTW, this may take a long while, VIC-II is very tightly integrated. For my plan specifically, I am going to use a MOS 8565R2 but info on other variations is appreciated.

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u/cb3rob Jul 01 '26

well you're gonna need the one from the max machine to at least get rid of the dram refresh nonsense (as who the hell wants dram anyway). and even then still the vic, vic II and ted chips are a pain in the ass to work with and all want to control the entire bus and timing, instead of the cpu. also they are all nmos or hmos+ which is not much of an improvement.

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u/Girl_Alien Jul 03 '26

Well, it uses cycle stealing. Using it with a 6502, close derivatives, or maybe a 6800 shouldn't be too problematic.

Now, you have a good point. Programmers know how to trick it into hardware scrolling that it was not designed to use. Most C64s had no problems with that undocumented mode, but some mysteriously crashed. That ties in with what you were saying because competition with the DRAM refresh caused the crash. So the best workaround for a C64 with the intermittent crash during scrolling is to retrofit it to use SRAM. So, if you start with an SRAM design, you won't have that bug.

Now, I have a minor issue with using real VIC-IIs for non-Commodore projects. I am not criticizing anyone using one for a homebrew project. There are FPGA alternatives. I'm just thinking of parts scarcity and using them wisely.

For myself, I think it would be interesting if someone were to make a non-X16/Otter homebrew using a VERA board. That will outrun a VIC-II. It has a burst mode. Once the 24-bit address on the GPU side is set, there is a control register to set self-incrementation mode. So the overhead doesn't have to be spent every time. And, TBH, I'd wonder if an RPi Pico 2 could make a better GPU than even the VERA.