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I've been told that it takes about 200 clock cycles to read from memorym, and somewhere around 1,000,000 clock cycles to read from HDD.
Does anybody know what the comparable number of clock cycles would be to read from SSD?
Jared
Posted 2010-01-14T03:52:27.893
Reputation: 181
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Those are arbitrary numbers that professors in college state to show how heavy IO code might not be worth wasting time optimizing as it's dependent on the drive speed anyway. Compare the transfer speed of a SSD and a regular Hard Drive. Divide your clock cycle figure that you have by the amount of times the SSD is faster than the Hard Drive. There you go, that's your new "clock cycle" amount. It's still large.
It has more to do with the interface. For instance SSD over SATA, and SSD over PCI-E is a huge difference.
Marcin
Posted 2010-01-14T03:52:27.893
Reputation: 3 414
I don't think you can simply go by transfer speed because the SSD won't have to deal with rotational latency or seek time.
BTW, this discussion did in fact come up in a Computer Architecture course. – Jared – 2010-01-14T04:02:43.270
@Jared: he's saying there's a good measure of arbitrariness in the "average" numbers your question quotes; with that in mind, using the transfer speed comparison would allow you to calculate a reasonable guesstimate for the SSD's clock-cycle-access-time. for hard, real-world clock-cycle access numbers you can't lump the categories together like that; you have to consider & test specific products. if you want to compare guesses, compare guesses; if you want real numbers, go collect some data. – quack quixote – 2010-01-14T06:06:19.153