[Coco] What about the double speed upgrade?
L. Curtis Boyle
curtisboyle at sasktel.net
Thu Jan 4 19:04:59 EST 2007
On Thu, 04 Jan 2007 17:29:36 -0600, Joel Ewy <jcewy at swbell.net> wrote:
> It's been a while since I looked at Sockmaster's 4MHz upgrade, but IIRC,
> it increases the clock speed for the CPU only. E remains at 2MHz for
> the rest of the system.
> However I also seem to remember that much of the speed increase would be
> lost on the 6309. I don't recall the exact details right now, but
> essentially it had to do with the fact that the upgrade inserts extra
> clock pulses during certain phases of the instruction cycle. On the
> 6809 these would have the effect of speeding up some of the internal
> processing that the CPU does between bus accesses. But when the 6309 is
> running in native mode, it already does some of this processing in fewer
> clock cycles anyway, so you don't gain as much. On the other hand, it
> would give you some of the same benefits of running in native mode even
> when you're running BASIC programs, etc. And the 63C09 is rated for a
> higher speed than the 68B09, so you wouldn't be overclocking it as
> much. I realize these details are incomplete. Somebody help me out if
> they are incorrect.
Sock's (and Bob Puppo's before him) clock doublers only double the
speed when the CPU is not accessing RAM. So, you are right, in 6309 native
mode, where the chip caches the instruction byte, you don't see as much of
a gain (except on many cycle CPU instructions that don't touch RAM, like
DIVx and MULD instructions). On things like TFM, it won't speed up at all.
L. Curtis Boyle
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