A multi-core 6502...would that be possible

[dmsc]

Hi!

On 10/16/2022 at 7:58 PM, Spaced Cowboy said:

The "over the horizon" thoughts I've had along those terms is to implement the 6502 core (I already have that from a previous project), link it up to (say) 8K of 1-cycle block-ram in the FPGA so it's not limited by RAM speed, and run it at ~75MHz because that's what the fabric will support.

 

The interface to the board will mean I have to write a programming language anyway (kind of similar to a modern BASIC/C hybrid, compiled so I get half of zero-page to play with) in order to maximise performance. The memory-dynamics of the 6502 mean you want to get the best out of zero-page RAM that you can, and given that I can export zero-page to be hosted by the FPGA, the long-term plan is to have a language that understands and takes advantage of the capabilities of the bank-switching that the hardware can perform. 

 

I have a proposal: Porting FastBasic to an FPGA  

 

FastBasic compiles the BASIC code to a very simple VM, it could be possible to implement a CPU in the FPGA that directly executes the FastBasic bytecodes. This would be really fast - as currently each VM instruction uses a minimum of 30 cycles only to increment the PC and call the implementation and return. This would work similar to how the ARM Jazelle instruction set worked.

 

I actually have tough of doing this for a while, while porting FastBasic to my own 6502 FPGA computer. The main advantage is that I already have the compiler working in the Atari, so I won't need any external tools for development, and the language would be 100% compatible between 6502 interpreted or "accelerated".

 

Have Fun!

 

[777ismyname]

On 10/16/2022 at 5:25 PM, Chilly Willy said:

I think the most interesting idea is to start with the existing A8 core for something like MiSTer and then start making improvements as if this were a real Atari in the 80s. Add another POKEY for stereo. Double or quadruple the speed of the chips.  Make derivations of the existing graphics to take advantage of the speed. Make the 6502 dual core. What Atari MIGHT have done to improve the A8 instead of just more of the same.

Doesn't the EclaireXL do that, at least to a degree? Man oh man, I'd LOVE to have an EclaireXL!

What you've mentioned here is what I've thought about for many years. Something as small as doubling the bandwidth of GTIA & Antic, maybe the 6502 to 7.16Mhz, would be really great to me.

 

[+Stephen]

4 hours ago, 777ismyname said:

Doesn't the EclaireXL do that, at least to a degree? Man oh man, I'd LOVE to have an EclaireXL!

What you've mentioned here is what I've thought about for many years. Something as small as doubling the bandwidth of GTIA & Antic, maybe the 6502 to 7.16Mhz, would be really great to me.

 

Yes - it's a wonderful thing.  On the fly switching of PAL/NTSC.  Ability to have stereo PoKey.  CPU multipliers up to 32X.  GTIA/ANTIC multipliers of 2X, 4X.  Real SIO peripherals and real controllers, and real carts supported.  It's a kick ass system.  Had mine since 2017.

 

https://www.flickr.com/photos/75619516@N06/36247463563/in/album-72157684901793962/

 

[777ismyname]

On 9/8/2023 at 1:51 AM, Stephen said:

Yes - it's a wonderful thing.  On the fly switching of PAL/NTSC.  Ability to have stereo PoKey.  CPU multipliers up to 32X.  GTIA/ANTIC multipliers of 2X, 4X.  Real SIO peripherals and real controllers, and real carts supported.  It's a kick ass system.  Had mine since 2017.

 

https://www.flickr.com/photos/75619516@N06/36247463563/in/album-72157684901793962/

 

Want to sell it?  I certainly wish someone would make another few in a batch! Have you played about with the graphics with the 2x or 4x increase?
 

 

[+Stephen]

Definitely don't want to sell it.  I messed with the accelerated graphics modes a little bit, and wrote a little debug utility to show some bugs when accelerated CPU was used (it broke some GTIA timing IIRC).  But I didn't do too much with it, as I started messing with the VBXE upgrade as it has a much higher install base, and I would like to see it get even more popular and I figure the only way to really sell hardware is to have software for it.