The second thing I should point out is that I haven't actually committed to doing any Atom optimization for either Altirra or VirtualDub. Also, as I noted, this function was #2 on the sampling profile, so if I needed to reduce CPU usage lower, this function would absolutely be on the optimization list. Reducing CPU usage further allows the CPU to drop to lower performance states more often, and 30 million cycles is more of a deal when the CPU is running at 400MHz instead of 1.6GHz. In other words, I hate it when my laptop becomes hot and loud, and I want programs to use less CPU even if there's more available. However, when it comes to optimizing for netbooks, or even just laptops, power consumption and heat production come into play. If it were just a question of attaining target performance this wouldn't be an issue at all, because Altirra already runs at full speed on the machine in question. If you think this isn't much, you're right - except that we're talking about a CPU designed for low-power netbook use. At ~2000 cycles per iteration, that's just under 30 million cycles, which is about 1.9% of 1.6GHz. This routine is one of the scan line renderers in Altirra, so it does indeed execute frequently - 240 * 60 = 14,400 times per second at peak. There was a lot more feedback than I expected on the Atom post ( ), so time for part 2.įirst, some more explanation. ¶Optimizing for the Intel Atom CPU, part 2
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