Can the Atari 2600 emulate the Commodore 64?

[Mr SQL]

It is possible for the Atari 2600 to emulate complex Commodore 64 video games with advanced graphics and sound.
Here is a white paper with workstages from the Fjälldata 2025 competition:
https://relationalframework.com/Emulati ... i_2600.htm

This technique is similar to emulating arcade games that use the 6502 on the C64 and Atari 800.
VM's for the sound and graphics chips allow the same code to run with only enough of the system bus emulated for the game.

AI perspective

[BigDumbDinosaur]

That’s not emulation, as the Atari 2600 doesn’t have the sound and graphics hardware of the C-64.  At best, I might call it a simulation.

Incidentally, the AI diatribe mistakenly implies the 6510 in the C-64 has more capability than the 6502.  Both MPUs have the exact same instruction set.

[Mr SQL]

BigDumbDinosaur wrote:

That’s not emulation, as the Atari 2600 doesn’t have the sound and graphics hardware of the C-64.  At best, I might call it a simulation.

Incidentally, the AI diatribe mistakenly implies the 6510 in the C-64 has more capability than the 6502.  Both MPUs have the exact same instruction set.

Agree you could call it simulation.

The Atari 2600 and C-64 hardware are similar in that both have independent hardware for sound and graphics/sprites.

This BASIC abstracts the hardware using the sound and graphics coprocessors to create cycle perfect VM's for the 6502 program to talk to.

I'm working on a devkit for the Atari 400/800 but it would be difficult to apply to Apple or ZX-81 home computers without adding dedicated graphics and sound chips.

This simulation/emulation has the advantage of running on a real CRT so the phosphor is perfect at high frame rates which traditional emulators cannot do yet.

[J64C]

BigDumbDinosaur wrote:

Incidentally, the AI diatribe mistakenly implies the 6510 in the C-64 has more capability than the 6502.  Both MPUs have the exact same instruction set.

The diatribe doesn't say that at all. The 6510 does have more capability than the "simpler '6502' variant" processor.

The Atari 2600 uses a 6507.

The key differences being-

• Address lines: 13 vs 16
  Addressable RAM: 8K vs 64K
  Internal IO Ports: 0 vs 2
  IRQ pins: 0 vs 1
  NMI pins: 0 vs 1
  AEC pins: 0 vs 1

Same instruction set and similar internal structure, but that's where it ends.

BigDumbDinosaur wrote:

That’s not emulation, as the Atari 2600 doesn’t have the sound and graphics hardware of the C-64.  At best, I might call it a simulation.

You couldn't even go close to even 'simulating' a C64 on an Atari 2600, due to it's less capable CPU (and peripheral hardware).

The link in the original post is describing a conversion of a C64 game to Atari 2600, not an emulation. A lot of the code is reusable, having only to address the audio and graphical limitations of the target device.

[Mr SQL]

J64C wrote:

BigDumbDinosaur wrote:

Incidentally, the AI diatribe mistakenly implies the 6510 in the C-64 has more capability than the 6502.  Both MPUs have the exact same instruction set.

The diatribe doesn't say that at all. The 6510 does have more capability than the "simpler '6502' variant" processor.

The Atari 2600 uses a 6507.

The key differences being-

• Address lines: 13 vs 16
  Addressable RAM: 8K vs 64K
  Internal IO Ports: 0 vs 2
  IRQ pins: 0 vs 1
  NMI pins: 0 vs 1
  AEC pins: 0 vs 1

Same instruction set and similar internal structure, but that's where it ends.

BigDumbDinosaur wrote:

That’s not emulation, as the Atari 2600 doesn’t have the sound and graphics hardware of the C-64.  At best, I might call it a simulation.

You couldn't even go close to even 'simulating' a C64 on an Atari 2600, due to it's less capable CPU (and peripheral hardware).

The link in the original post is describing a conversion of a C64 game to Atari 2600, not an emulation. A lot of the code is reusable, having only to address the audio and graphical limitations of the target device.

The emulation/simulation is closer to the CHIP-8 VM:
https://www.youtube.com/watch?v=e-G6Dm5AX3I&t=499s

Chip-8 is an excellent starting point for learning about writing emulators.
You may find it interesting Chip-8 became full Framework emulation by deprecating escaping to Assembly. This allowed different processors to fully support Chip-8 [Framework] emulators.

For example you can play the same Chip-8 games on the VIC-20 that you can on the C64 because they can both run the Chip-8 Framework VM [emulator/simulator].

The Framework emulated for this game similarly runs the same code except better graphics and sound than Chip-8. I don't think the VIC-20 is powerful enough to run this games Framework because it doesn't have the sprite hardware over semi-graphics to abstract but the Atari 800 could.

[J64C]

So, an emulator that emulates and Atari emulating a C64.

The AI was right. You can’t emulate a C64 on an Atari 2600.

[Mr SQL]

J64C wrote:

So, an emulator that emulates and Atari emulating a C64.

The AI was right. You can’t emulate a C64 on an Atari 2600.

This is related to your observation earlier "having only to address the audio and graphical limitations of the target device".

COSMAC-VIP games and RCA Studio 77 console games are both Framework games that can run CHIP-8 Source on either system.

For the concept to work on the Atari 2600 and Commodore 64 hardware this Framework is limited to 160x100 graphics while the C64 can display 320x200.

It can render animation at this lower resolution with a higher framerate than is possible at 320x200 so is a good platform for high fps demos and 3D video games like the Star Raiders Cover.

It is interesting to create games on one platform (the Atari or the C64) and then take the development to the other system. I think it adds more to creative design than developing for either system alone.

Here is the latest binary for the Star Raiders Cover with cumulative enhancement:
https://forums.atariage.com/topic/37879 ... nt-5628919

[J64C]

Mr SQL wrote:

It is interesting to create games on one platform (the Atari or the C64) and then take the development to the other system. I think it adds more to creative design than developing for either system alone.

How do you address the RAM limitation 8K vs 64K and the lack of 4 VIA ports (2 on the CPU and the other 2 in hardware)?

The only thing the two systems have in common is the instruction set. That's where the similarities end.

[Mr SQL]

J64C wrote:

Mr SQL wrote:

It is interesting to create games on one platform (the Atari or the C64) and then take the development to the other system. I think it adds more to creative design than developing for either system alone.

How do you address the RAM limitation 8K vs 64K and the lack of 4 VIA ports (2 on the CPU and the other 2 in hardware)?

The only thing the two systems have in common is the instruction set. That's where the similarities end.

Great questions.

If the game grows too large it will only run on the C64.

The resoures supported by the Framework VM are the Joysticks and console switches.
The BW/Color console switch is mapped to shift-lock key on the C64 keyboard and both machines have Joysticks.

The similarities for sound and graphics are excellent.

Both machines have multiple oscillators for sound to support the Tracker and low-level shadow registers.

Both machines have higher resolution sprite hardware over low resolution playfield semi-graphics.

This graphics hardware interfaces with a 6502 blitter in the VM.