Posted By
JamesD
on 2017-02-17
10:47:26
|  Re: A mathematical demo
> I used Xroar. Why are you so sure that a genuine Dragon can't run at 1.7MHz? Why the idea about self-refreshing code looks wrong to you?
I'm sure because someone spent weeks trying self refreshing code.
That doesn't mean it's not possible, just that we couldn't get it to work.
YMMV
>I am curious why Japanese didn't make fast 6502 too? They made fast z80 (R800), fast 6809 (6309), fast 8088 (v20), fast 8086 (V30) but missed 6502. 
Hitachi was a 2nd source for chips from several companies at that time. That may be why you see support for certain chips and not others.
MOS was owned by Commodore, and Synertec was a 2nd source already.
Western Design had Rockwell as a 2nd source. Rockwell added additional instructions to the 65C02.
Plus, the 6502 was cheaper than the other chips, negating the need.
There probably wouldn't be a faster part for the 6502 anyway. It already had a prefetch and short instruction cycle times. The prefetch alone speeds up the 6309 and 64180 by a clock cycle for almost every instruction. Not sure how they could have added a multiply unless they used A and X.
They microcoded the HD64180, added a prefetch, and used a wider ALU. Speed optimization was easier to come by there.
Hitachi also had a 6303. It's a drop in replacement for the 6803... though I vaguely remember 1 pin possibly being slightly different. Nobody's found a native mode switch for it like the 6309, though I'm not sure anyone has even tried to find one. It it exists, it might add a prefetch.
I might get around to looking at the 6809 code, but I have a lot of other things I need to do first.
|
