I really like the system he uses to access video RAM which is simple, decouples the video from the main RAM (which is a serious weakness of real 8-bit machines because it hurts non-video performance directly as well as limiting the clock speed) but is also high performance (if you are blasting out a block of data to the video you can just blast out the bytes to a memory mapped location and the address pointer counts up automatically.)
This was standard on the PC-Engine, and I think the majority of VDC type display controllers of the time.. Personally, I’d take a bank switching scheme whereby CPU reads come from RAM as standard and CPU writes go to graphics memory.. Even as simple as 1 bit mapping of writes to either CPU RAM or VDC RAM would suffice well.. Though more complex is possible..
> So performance was their goal, right? Well, if so, then why use a 65C02 CPU
Because it makes the computer as compatible as possible with Commodore software back in its day. Ports become simpler.
If you watched the video, you would have seen they changed the design considerably and came up with a basic that is compatible with VIC-20, C64 and similar machines. So you can run most Basic programs without changes. He also ported his modern Commodore game „Attack of the Petscii Robots“ to the X16 because he did not have to write its source from scratch.
I thought the point about being able to just put the rest of the system on the fpga was interesting. especially in light of his plans to potentially get an asic (which i also seriously doubt will happen for a niche product like this). I guess if your board is just an fpga and support circuitry, it won't feel very retro and cool, but if that's the long term trajectory, they could have probably reduced costs a lot by just doing that to begin with
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If you watched the video, you would have seen they changed the design considerably and came up with a basic that is compatible with VIC-20, C64 and similar machines. So you can run most Basic programs without changes. He also ported his modern Commodore game „Attack of the Petscii Robots“ to the X16 because he did not have to write its source from scratch.