[Coco] What about the double speed upgrade?
jcewy at swbell.net
Thu Jan 4 22:52:14 EST 2007
Thanks for confirming my recollection. And what I didn't make as
explicit as I could have was that since the E clock remains at the 2MHz
rate for the rest of the system, there shouldn't be any hardware
incompatibilities, unless some weird hardware was counting on certain
minimum delays between accesses while the CPU is ruminating over the
next address to put out. But if there were any such hardware, it would
also have problems with the 6309 running in native mode. So you really
only have to worry about timing loops, I would think.
L. Curtis Boyle wrote:
> 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.
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