Greg,
Your idea would probably work assuming that all chips are equal, but they're not.
I don't know that this is all accurate, but from I've read read over the years, this is how they decide which processor is which. This applies to Intel and I assume also to AMD.
They create a large "batch" of CPUs and then take a representative sample and test them (I don't know how or how many). During their testing they determine that all of their samples will run *within specifications* at, say, 800 MHz. So all of these are put out as 800 MHz. processors. Maybe the next batch will test higher and be 900 MHz., etc. You can see the possibilities...maybe some of the chips will actually run higher.
Then you take marketing/sales into account. *Perhaps* they need more 800 MHz. chips, but their yields are really good and they take a batch that tests at 900, and set them up and package them as 800's. For all I know, they may determine that they need 800 MHz. chips and not bother to test them any higher. Obviously they make more money selling faster chips, and it probably costs the same to make each chip.
By the time you get the cpu, you're not quite sure what you have, except that the manufacturer guarantees that it will run at a certain minimum speed, within its specifications. It's possible that you could just do what you suggested, close the bridges on the AMD chip and slap it in without changing anything else. (I haven't really followed that type of change, so I <i>assumme</i> that it would be enough to tell the BIOS the new multiplier, but I don't know).
But whether you change the multiplier via the jumpers or the BIOS, you are now running the physical cpu outside of its tested environment. Maybe it will work and maybe it won't. Maybe it will work if you up the voltage...further placing it outside of the tested environment. And as you pointed out, higher voltage means a hotter cpu.
Finally, as you get closer to the physical limits of the cpu making process, your chances of overclocking are slimmer.
I'd much rather make the changes in the BIOS. :^)
I'm certainly open to any corrections or other theories.
BTW, I believe they use a similar "culling" process when they make RAM chips.
Mike