[Coco] 6809's CWAI & SYNC ops

[Boisy G. Pitre]

This question is very close to the work I did on my thesis, "Compiler-Assisted Energy Reduction for Microprocessors: Measurement and Analysis" back in 2010. For that work, I measured the power dissipation of the 6309 (not the 6809) using various instructions.

I pulled out my thesis book and looked it up. On average, CWAI (18 cycles) consumed 6.771 milliwatts of power on a 6309 running at 1.78MHz. In relation to that, NOP consumed 8.758 milliwatts, LDQ #$0456B56A consumed 11.148 milliwatts, and the DIVQ instruction consume 14.104 milliwatts.

So for the 6309, there appears to be some power savings using CWAI, but as far as the chip running cooler as a result, I don't know, I didn't take temperature measurements.

On Mar 4, 2013, at 9:20 AM, john dumas <JohnDumas at austin.rr.com> wrote:

> On 3/4/2013 8:39 AM, Brett Gordon wrote:
>> Here's a question:
>> 
>> Does the 6809 or 6309 operate any cooler during the duration of a CWAI
>> or SYNC op ?   Has anyone done any testing?
> For the 6809(E), probably not.
> For CMOS power dissipation is pretty much a direct function of
> frequency - charging/discharging of parasitic capacitance and the
> DC current that results when the P and N channel xistors are both
> on during a logic level change.
> 
> The situation is different for depletion load NMOS (6809). In that case
> current ALWAYS flows thru a gate when it's output is at ground. One can
> assume that maybe 1/2 the gates will always be at that level at any one time.
> The current is set by the W/L (resistance) of the load xistor and swamps out
> the charge/discharge current of the parasitic capacitance on the node.....
> 
> Unless Bryant took some special care in the electrical design to "turn off"
> sections of the logic during the wait and sync, you should see little difference
> in power dissipation. [During the design phase, I never heard any discussion
> from Terry or Bryant about such a power saving feature. Not saying it didn't
> happen, but I would think they would have bragged - especially Terry! - about
> their innovation, if it existed.......]
> 
> FWIW,
> johnd
> 
> 
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