I was reading On the Edge: the Spectacular Rise and Fall of Commodore the other day, and I noticed something interesting:
Perhaps patents are the reason that the 2A03 has no decimal mode, instead of needing room for the sound generators and timers. Also, I wonder what bugs/timing differences are in the 2A03 that aren't in the normal 6502s. The last sentence indicates there would be some.
Brian Bagnall wrote:
[In 1986,] Commodore management began to consider options to compete against Nintendo. . . Robert Russell investigated the NES, along with one of the original 6502 engineers, Will Mathis. "I remember we had the the chip designer of the 6502," recalls Russell. "He scraped the [NES] chip down to the die and took pictures."
The excavation amazed Russell. "The Nintendo core processor was a 6502 designed with the patented technology scraped off," says Russell. "We actually skimmed off the top of the chip inside of it to see what it was, and it was exactly a 6502. We looked at where we had the patents and they had gone in and deleted the circuitry where are patents were."
Although there were changes, the NES microprocessor ran 99% of the 6502 instruction set. "Some things didn't work quite right or took extra cycles," says Russell.
The excavation amazed Russell. "The Nintendo core processor was a 6502 designed with the patented technology scraped off," says Russell. "We actually skimmed off the top of the chip inside of it to see what it was, and it was exactly a 6502. We looked at where we had the patents and they had gone in and deleted the circuitry where are patents were."
Although there were changes, the NES microprocessor ran 99% of the 6502 instruction set. "Some things didn't work quite right or took extra cycles," says Russell.
Perhaps patents are the reason that the 2A03 has no decimal mode, instead of needing room for the sound generators and timers. Also, I wonder what bugs/timing differences are in the 2A03 that aren't in the normal 6502s. The last sentence indicates there would be some.