Untapped Potential of the 2600 and similarities to the NES

[briguy578]

Something I've been wondering about that I would like to muse on a bit.
The Atari 2600 and the Nintendo NES both use the same microprossor, the 6502. The NES's greater power comes from the extra RAM, larger cart sizes and improved sound and graphics chips.

However, I know from the several "RAM plus" games made and from the add-on abilities of the supercharger that the Atari 2600 was capable of a lot more then it seemed.

So basically, I am wondering if, with enough extra RAM and a POKEY chip in the cart if NES type games could be possible on the Atari 2600.

Secondly, with the similarities in arcetecture, could someone make an Atari 2600 adaptor for the NES?

[soniko_karuto]

i believe the adapter for the nes wont work.

because of the way it handles graphics, i belive, you had to write to the screen every line or so. so the nes is tile based and it wouldnt work i believe.

[rbudrick]

From What I understand, they do not use the same processor, but they do get programmed in the same language...6502 assembly. Actually, the A2600 uses a variant of 6502 known as 6507. I don't believe it was used in anything else...

These systems have very different architechture. The way you address each piece and section of hardware and the way each machine interprets these instructions is EXTREMELY different. The atari isn't even a tile based system.

-Rob

[davidbrit2]

Yeah, the TIA is WAY different from a sprite/tile-based GPU like in the NES. You could theoretically put another processor on the cart and have it take some load off the 2600's CPU (since it has to do all the rendering in real-time), and you might be able to get some slight improvements, but then you'd have to have a 2600 program that does the rendering from cart RAM, and another program for the secondary CPU to do whatever it plans on doing. It would be way too much trouble, in other words. Heh.

Oh, and I believe the main difference between the 6507 and 6502 is that the former has no interrupt support. That's not anywhere near the weakest link of the 2600's architecture, though.

[SoulBlazer]

What would you say WAS the weakest link? The lack of memory?

[Great Hierophant]

Don't forget that an Atari can only access 4k of ROM due to its processor while a NES can access 10x that without any extra hardware. Also, the Atari's 6507 supports a decimal mode while the NES's 2A03 does not.

[davidbrit2]

What would you say WAS the weakest link? The lack of memory?

I'd say it's the total lack of a real GPU. The TIA is basically just a chip that paints individual scan lines and changes color mid-line based on the values of a handful of registers. So for EVERY video frame, you have to do your meaty game logic during the vertical blanking period (the pause between individual frames being drawn), then the program has to focus completely on setting the right register values in the TIA for every single scan line as the frame is drawn. Oh, and if the program takes too long to finish working before the next scan line starts drawing, you get all sorts of weird (and ugly) results. And of course, this has to be done for all 200+ scan lines for the video frame. So there's very little time for the <2 MHz CPU to get much work done for each frame. This is why games like Quadrun have to blank the screen when doing speech synthesis: there's not enough CPU cycles to play the audio and draw anything meaningful on the screen at the same time.

If I'm not mistaken, the 7800 is little more than a 2600 with a Maria graphics chip, and probably a little bit more RAM. Other than that the sound hardware is identical, and the CPU is pretty much the same, though possibly with a slightly higher clock rate. Consider that, and then compare 7800 Xenophobe to 2600 Xenophobe. ;-) Having only 128 bytes of main RAM would probably be more than enough if the 2600 had a GPU with one or two KB of RAM to hold tile and pattern data.

[BigGeorgeJohnson]

Here are the specs that I have.

Nintendo NES (1985)

CPU
MOS 6502
1.79MHz

Graphics
8-bit 8-Bit PPU
256x240 Resolution
16/52 Colors
64 Sprites
8x16 Sprite Size
2KB Video RAM

Sound
4 Channels

Data
2KB Main RAM
Cartridge (512KB)

Atari 2600 (1977)
CPU
MOS 6507
1.19MHz
8-bit

Graphics
16 Colors
Sound
2 Channels

Data
Cartridge

Atari 5200 SuperSystem (1982)
CPU
MOS 6502C
1.79MHz
8-bit

Graphics
320x192 Resolution
16/256 Colors

Sound
4 Channels

Data
2KB Main RAM
Cartridge


Atari 7800 ProSystem (1986)

CPU
MOS 6502C
1.79MHz
8-bit

Graphics

MARIA Processor
320x200 Resolution
16/256 Colors
100 Sprites TIA Chip

Sound
4 Channels

Data
4KB Main RAM
Cartridge

Of note the SMS was packing some serious ram for it's time.

Sega Master System (1986)

CPU
Z80
3.58MHz
8-bit

Graphics
256x192 Resolution
52/256 Colors
64 Sprites
32x32 Sprite Size
16KB Video RAM

Sound
4 Channels

Data
8KB Main RAM
Sega Card (32KB)
Cartridge (512KB

[davidbrit2]

Atari 2600 (1977)
CPU
MOS 6507
1.19MHz
8-bit

Graphics
16 Colors
Sound
2 Channels

Data
Cartridge


It's actually capable of something like 128 different colors. And the RAM size is 128 bytes.