tepples wrote:
koitsu wrote:
So the logic here is that because the processor technology (specifically NMOS 6502) and architecture was developed in 1975, that the system/console itself is a "70s computer"?
The CPU is the only part of the console that interacts with the CF card, and the CPU was invented in the 1970s. It's the same CPU that Atari had used in its Video Computer System model 2600, just 50% faster.
There are two things to deal with: the instruction set and the microarchitecture. A modern Athlon family CPU has vastly different microarchitecture from an 8086 while using the same instruction set, involving simultaneous out-of-order processing of instructions. The 2A03, on the other hand, is gate-for-gate the same as the 6502 mask with the decimal mode circuitry disabled.
processor.
Along those lines, doesn't the 2A03 have additional instructions (and undocumented instructions/opcodes) when compared to the 6502A? I recall it having additions to deal with the PPU and video circuitry or something, but I'm tired and could be delirious.
What would happen if you dropped an 6502A into the 2A03 pads and tried to run with it? Further, with the instruction compatibility of the 65C816, what if you wired one of those beasties up to the NES (aside from timing differences, anyway)? I expect that the extra instructions are mandatory, if my memory is right, to run anything graphical, but I could be severely mistaken.
I recall that the choice of the 65C816 over the M68000/020 on the SFC/SNES was for ease of porting titles in development (e.g. 'Super Mario Bros. 4/SMW') to the new hardware, as the '816 offers both all the 6502 instructions plus new additions in 16-it mode and full 6502 backward-compatibility mode as well. Thus, while the 68020 was a better technical choice, the 65C816 allowed for faster conversion of games to be made available at launch and was also a less expensive part.
The neat thing is that the '816 was made up to 20MHz and is still available today for anybody twisted enough to want to seriously rewire their SNES with some extra horsepower, although it'd be entirely CPU internal, as the rest of the bus timing would rely on the original clock rate. Still, that would be neat for certain CPU rendering operations, I'd imagine, if you wanted to go nuts with it.
Anyhow, bed is calling for me. If you celebrate something today, happy whatever-it-is-you-celebrate. My holiday for the month is now three weeks past.