I found this in the December 1984 issue of Byte Magazine, part of a large interview with Steve Wozniak:
Quote:
BYTE: Are you thinking about using the new 65816 processor for anything?
WOZNIAK: We're thinking about it and doing some R&D with it, but I don't know if we'll use it. Anything we do has to be compatible with the Apple II. If we found out that the 65816 wasn't, it would be a serious question. It's too new a part right now.
Maybe this was at the stage where the timing issue affected the disk interface and Woz was aware of this. Interesting though that Apple very strongly wanted backward compatibility. The Macintosh was originally going to use the 6809, it would have been interesting if they had of considered the 65816 at the time.
Quote:
BYTE: How is its performance compared to the 68000?
WOZNIAK: It should be available soon in an 8-MHz version that will beat the pants off a 68000 in most applications, and in graphics applications it comes pretty close. Some of the Macintosh people might disagree with me, but there are ways around most of the problems they see. An 8-MHz 65816 is about equivalent to a 16-MHz 68000 in speed, and a 16-MHz 68000 doesn't exist.
This is probably overstating the speed difference a bit, but it's interesting to speculate on this. The Macintosh had 512x342 mono graphics, and 128k RAM. When the IIgs came out it had 640x200 color graphics and a lot more RAM, 256k to start, but expandable to over a megabyte. It's speed was somewhat artificially limited to 2.8 MHz and it still managed to run Macintosh like software at reasonable speeds. I've got an emulator that has an option to run at 8 MHz, at that speed the graphics performance is really quite good. The biggest difference was that the 68000 had a much better growth path for the future, but it's interesting to speculate if the 65816 came out a little sooner what would have happened.
One thing that has always put off people about the 65816 is the banked architecture. I found this in the Apple /// Business Basic source code:
Quote:
;I WISH I WERE A MOTOROLA 68000,
;YES THAT IS WHAT I'D TRUELY LIKE TO BE,
;CUZ IF I WERE A M. 68000.
;EVERYONE WOULD LOVE TO PROGRAM ME!
32-bit registers and no need for banking is definitely appealing to a programmer, but on the other hand the 65816 was a very efficient processor. I've been doing a lot of thinking about how best to organise a 65816 system and I guess the learning curve was quite high, but now I think that it's quite a nice system to program. In the x86 world they had more 'nastiness' to deal with and that worked out fine.