Abbuc Hardware Contest 2008...

[Rybags]

The best method would be to have latches, which could be set by a $D5xx write.

 

By default, they could assert Reset on the external CPU.

 

So, the Atari would just need to page in the area of RAM where the other CPU would look for it's vectors, and upload the firmware.

 

Of course, there could always be the option to have resident firmware.

 

For the Atari to be able to read/write to the external RAM, then you'd need a latch to hold it in a Halt state.

[+bob1200xl]

I think a 14mhz 65816 with 512K of memory is reasonable - not all in a cartridge, though. You might be able to cram it all in there but you would probably have thermal problems, too much current drain on the 6502 system and little or no expanability. It's going to have to be in its own chassis.

 

Memory sharing works by halting the 65816 when the 6502 wants access. Not a problem. We do that now with ANTIC - same process.

 

The 65816 would be halted until the 6502 has loaded its memory. Then, you just start its clock and let it run.

 

Bob

 

 

Yes. A full processing slave.

 

SIO would be unchanged on the 6502. If you wanted to 'put' a block of data to the 65816, you would enable 8K of 65816 memory in one of the two segments and just read/move data into the block. No OS changes are needed. To 'get' a block of data from the 65816, you just enable and write/move data.

 

I like this idea. Add a faster CPU (make it a 65816 so the programmers aren't learning something totally new) with some memory (1/4/8/16 MB?) into a cartridge. Allow the user to swap in any 8k bank into $A000 and/or $9000 (make them bankable seperately), and also allow the 6502 to access this memory as well. For games, I could see tons of benefits.

 

You could upload all your graphics data to the cartridge, and then during the VBI tell your cartridge 65816 CPU to move on-screen objects (even PMG!) and then ANTIC could display from somewhere in the $9000-BFFF range, use a charset or PMG area in that range. It could be used like a Blitter chip, or sort of a video co-processor. The great thing is that the utility of such a thing is totally up to the programmer.

 

Is this just pie-in-the-sky though? Is it possible to design such a thing that will fit in a cartridge and be powered from the atari? I'm not really a hardware guy, but I imagine you'd have to have a way to "lock" the memory when each CPU is using it. Also, on the software side, you'd have to have some sort of "default" bootstrap code for the 65816 to run until code is put into it's memory by the 6502 and it's told to run something. Hmmm, how would that work best I wonder? Maybe by generating an interrupt on the 65816 after setting it's interrupt vectors or something? interesting... I'd like to see this made and get into the hands of some programmers!

 

I'd throw out all the ideas about CF cards, IDE drives, etc.. Try to fit it in one cartridge (or maybe a slightly larger cartridge). I'd even throw out flash memory. Make it strictly a co-processor board with it's own memory. Nothing else... keep it simple and cheaper. I think that's enough to create some really interesting possibilities. I don't like the thought of running a cable from a cartridge to an external box with additional gear in it... that's just me though. If it can't be done any other way though...

[+bob1200xl]

Yes. I don't see any advantage to resident firmware. Just load from the system and go from there. With its own power, the 65816 will retain its data when you power off the Atari, even.

 

You don't need to latch a Halt signal. The 6502 sees the memory just like any other RAM. All works transparently.

 

Bob

 

 

The best method would be to have latches, which could be set by a $D5xx write.

 

By default, they could assert Reset on the external CPU.

 

So, the Atari would just need to page in the area of RAM where the other CPU would look for it's vectors, and upload the firmware.

 

Of course, there could always be the option to have resident firmware.

 

For the Atari to be able to read/write to the external RAM, then you'd need a latch to hold it in a Halt state.