How many transistors in the 6502 processor?

I believe calling the 6809 a 16-bit machine is exaggerating somewhat. It had an 8-bit ALU and an 8-bit data bus, and an 8-bit almost everything else. Even the 6801 had instructions that would concatenate the A and B registers so a single instruction would operate on the pair, and the fact that the 680x series had a 16-bit index register was more of a hindrance than a help as far as performance was concerned. The instruction set was very nice, though. Although the "internal architecture" supported 16-bit operations somewhat, it's a bit of a reach to compare it with, say, the i8088, which, though I hate the segmented effective address computation scheme, is, in fact, a 16-bit architecture, as it has a 16-bit register SET, a 16-bit ALU, and 16-bit instructions that operate on 16-bit operands. The 6502 had advantages over the MOT-style processors primarily BECAUSE of its 8-bit index registers. Because the index registers were a single byte, the state machine that controls the physical address computation doesn't have to decide to skip a cycle when the MS byte of the index is zero, nor does it have to decide what else to do with the upper byte, since there isn't one. Its 8-bit character is what makes it faster than the MOT equivalents. It does 8-bit things VERY fast, so long as they are scoped into table sizes easily handlled with the 8-bit index registers. Any 4 or 8 bit processor can process 16-bit data, given enough time and resources. Some do it more elegantly than others, and I freely admit that the 6809 does it more elegantly. It just doesn't do the 8-bit stuff as fast as the 650x family. The fact is, the 650x family was a smaller chip than the MOT, Intel, or Zilog parts of the same class. That suggests it had fewer transistors, since the number of transistors would increase the chip size. Keep in mind, when considering this contrast, that the 650x's general purpose registers could be viewed to reside in the "zero-page" since the access to that region was faster than to the rest of memory. Having larger registers and more of them, as did the 8080 and Z80 certainly would make the chip larger and the transistor count larger. It has a pipelined data bus, which, in reality, is just double-buffer for the benefit of the instruction decoder, so it can decode the opcode WHILE the opcode's first operand, or the next opcode, is being fetched. While this doesn't speed up an opcode's execution in a test setting, it does speed up a sequential execution as you encounter when running code. If you look at what appears on the 6502's pins as it executes various instructions, you'll see that. (this is documented in MOS Technology's 6500-Series Hardware Manual, so you don't have to dig out the logic analyzer.) Dick ----- Original Message ----- From: "Eric Chomko" <chomko(a)greenbelt.com> To: <classiccmp(a)classiccmp.org> Sent: Friday, May 04, 2001 10:59 AM Subject: Re: How many transistors in the 6502 processor? many