Re: Apple II VGA Video Generator Card Project

[Alex Freed <alexf@mirrow.com>]

Great minds think alike :))

I was going to mention that I already have Verilog that does a good job
of showing standard Apple video on a VGA screen. I didn't do the double 
hires, but it is quite trivial to add.

So one simple way to do it is to put the smallest Spartan 3 or Altera 
Cyclon FPGA on a card. It has everything: enough RAM for the frame 
buffer, PLL to multiply the clock frequency and more than enough logic
to do the job. XC3S50-4VQ100C costs $10. That's the good part. The bad 
part is that soldering such chips is beyond hobbyist technology. At 
least for most people. So it has to be done professionally.

The beauty of the FPGA approach is that it is so flexible. You can 
always add a new video mode or what have you at any time. The character 
generator will also fit inside and can be re-programmed.

On the other hand if you have an FPGA, why stop at video generation when 
I have fitted the whole Apple 2 into it? And who needs accelerator chips 
if I can run my "6502" at 28 MHz clock? Probably even faster if needed.

Then again the VGA video card could be built with just TTL chips and 
GALs or a CPLD. Easier to assemble but a lot more parts.

BTW there is no need for dual ported RAM: 500 nS out of every 1 mS 6502 
does not acess the memory. That's how the normal Apple video works. 
Using modern SRAM it is trivial to read 4 bytes in 500 nS (double scan 
rate AND double hi-res or 80 columns).

I could make either a video for VGA or a whole FPGApple available 
commercially if I new there was a market.


aiiadict@gmail.com wrote:
> http://www.mirrow.com/FPGApple/screenshots.html
>
> http://www.mirrow.com/FPGApple/
>
>
> He's got apple II video displaying on a VGA screen, perhaps
> the code can be modified to work with dual port RAM in
> a real apple II
>
> Rich