I suppose it depends on how bandwidth limited S@H is in the current version. I hope someone can give a definative answer concerning that.
You see, with dual motherboards (you are obviously using an intel machine, because the dual athlon chipsets aren't out yet), the CPU's
share the bandwidth of the system. The more bandwidth, and low latencies that the program requires, the more of a dimineshing returns you'll see by running two instances of S@H. RC5 causes nearly no bandwidth overhead, and so runs on multiprocessors nearly flawlessly, and with near X times as much work done in the samme amount of time, where X is the number of processors.
S@H is (or at least, was), a different beast. With dual intel motherboards, the systems share the bandwidth of the memory. Prior clients used a lot of bandwidth, and liked low latencies. When two (or more) instances of S@H were run, this caused the CPU's to fight for bandwidth. If you are familar with economics (I can't believe how handy this course is coming in
), you can consider memory bandwidth, at least on an intel platform, to be a
rival good, whereby if one CPU is consuming it, it detracts from the other CPU's ability to consume it. This means that the output is nowhere near X times as much work where X is the number of processors in the system.
HOWEVER, the new clients are supposedly more bandwidth/latency friendly (though not nearly to the point of being like RC5, but that is intrinsic to S@H's nature), which mitigates, at least to some degree, the amount of bandwidth required. Also, CPU's with larger cache's (read: xeon's, Ultrasparcs, PA-RISC chips, etc) tend to deal with less bandwidth better, as they can rely on the larger L2 cache's than on system bandwidth (to some extent).
SO, if you have a dual system, with my current understanding of S@H, if I were to participate in both contests, I would put one CPU on S@H, and one CPU on RC5. This will allow you to get full S@H power from one CPU, and one full RC5 power from the other. IMO, this makes the most sense when looking at efficiency, and wanting to participate in both contests using multiple machines.
What I mean by that is, take a person with 2 dual systems. To participate in both contests (within this limited example), there are two options: 1) To have one dual system run RC5 on both CPU's, and one to run S@H on both CPU's, or 2) To have each dual system run one instance of RC5, and one instance of S@H.
The latter leads to the same production of RC5 (because of its almost non-existant overhead of bandwidth and low latency memory), HOWEVER, it would at the same time give way to MORE S@H units being produced than if one were to employ the former option.
I hope this diatribe was of some use....
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