# Thread: 7200 HDD converted to mhz

1. ## 7200 HDD converted to mhz

I believe I was reading some PC magazine and they had used some sort of formula to convert the RPM speed of a HDD into mhz. I was wondering if anyone else had read that or just knows the answer. I think they were saying that a 7200 RPM HDD ran at the equivalent to 150mhz.

2. Never heard of such a formula.
It sounds kind of hokey to me.

3. Yeah, it's not as if a hardrive has a clockrate.

4. MHz of what?? I'm not following at all.

5. You guys have to stop thinking pure computer and just general physics.

A hertz is a cylce/second of anything, not just CPU's.

Most North American Household power is supplied as 120V and 60Hz. The AC cycles 60 times/second.

If you take a 7200 rpm drive. That spins 7200 revolutions per minute. That equals 7200 revolutions per 60 seconds or 7200/60 = 120 revolutions per second. In otherwords 120 cycles/second or 120 Hz.

6. Originally Posted by Duner
You guys have to stop thinking pure computer and just general physics.
It could be a lot of things. That was the first conclusion that I came to, but since he said MHz, that would have to be something electrical.

Since they don't specify, it is difficult to figure out what there are referencing.

7. Originally Posted by Duner
You guys have to stop thinking pure computer and just general physics.

A hertz is a cylce/second of anything, not just CPU's.

Most North American Household power is supplied as 120V and 60Hz. The AC cycles 60 times/second.

If you take a 7200 rpm drive. That spins 7200 revolutions per minute. That equals 7200 revolutions per 60 seconds or 7200/60 = 120 revolutions per second. In otherwords 120 cycles/second or 120 Hz.
That sounds like what I had read. Thanks for figuring it out. So, based off of this formula, the HDD is the slowest part of the computer, right? Getting a SSD would effectively eliminate this sort of bottleneck. What would be the next slowest part in a computer, the Northbridge or Southbridge?

8. You can't say that since the drive is 120Hz that it is the slowest. It completely depends on what your doing.

If you are in a game, the biggest bottleneck isn't the drive, its the graphics card. If you are rending a 3d scene, the processor will be the bottleneck.

You are overgeneralizing everything....

9. There might be a rate that the drive sends data to the motherboard, but I think that would depend more on the type of connection then rotation speed.

10. Nope -Ridenow

11. Originally Posted by noegruts
Still nope
Sorry to be rude, but if you don't have anything to add to the thread, you shouldn't post

Agreed -Ridenow

12. Originally Posted by thideras
Sorry to be rude, but if you don't have anything to add to the thread, you shouldn't post
But he's right.

Anyway, yes the HDD is a big factor in limitation of your computer, but not in the way you are thinking of. SSD is currently one of the best ways to help loading times, boot times, and with a steady 90MB/s average read/write also great at transfers and installs. However it costs a load of money for little storage.

You can't generalize RPM speed to MHz anyway.

13. The HD may be a limiting factor in many scenarios but as Thideras pointed out it isn't always the limiting factor. In addition, even if it is the limiting component, converting the RPM to Hz doesn't mean anything other than a different way to measure RPM. It can't be compared to the frequency of a different part.

14. I tend to think of the Internet, and then the HDD as the biggest bottlenecks in PC's. But Thideras has an excellent point.

Just the rpm of a HDD says little about the performance except in a very broad sense. Sure 15k>10k>7.2k>5.4k, but there is a pretty wide margin of performance in the 7.2k category.

You still need more information like aerial density, cache, & actual performance stats like seek time, STR, etc.

15. Well, I only started this thread to find out if others had heard the same thing I had and if that had any sort of affect on performance.

16. It's just a different number to represent the same thing which is what I sort of said before. RPM, no matter which units are used to state it, is one part of drive performance like jason said.

17. You can't compare RPM and MHz because the units are different and there are no conversion factors you can use to go from one to the other.

Hz is a measure of oscillations. RPM is a measure of rotation. Something oscillating goes up, then down, while traveling across time - hence the waveform. Something spinning, doesn't go up or down - it goes around. And it goes around more as time goes on. They're fundamentally different measures and as such can't be compared.

If they were trying to equate anything between the two measures, it was just metaphorically, i.e. a 7200RPM drive is like a 2GHz C2D as a 15K RPM drive is to a 4GHz C2D.

Originally Posted by Duner
You guys have to stop thinking pure computer and just general physics.

A hertz is a cylce/second of anything, not just CPU's.

Most North American Household power is supplied as 120V and 60Hz. The AC cycles 60 times/second.

If you take a 7200 rpm drive. That spins 7200 revolutions per minute. That equals 7200 revolutions per 60 seconds or 7200/60 = 120 revolutions per second. In otherwords 120 cycles/second or 120 Hz.
The problem with your logic, along with what I mentioned above, is that the drive runs on DC, which has no waveform.

18. yes it runs on DC, but i think you miss the point, i believe he ment to be use it as an example.
I don't believe you can compare hz to hz here. sure you can say the frequency of the drive is 120 spins per second,(ideal conditions) but cpu, and gpu's process way more MB/s of data per "hz" if you will.

19. Originally Posted by imposter
yes it runs on DC, but i think you miss the point, i believe he ment to be use it as an example.
I don't believe you can compare hz to hz here. sure you can say the frequency of the drive is 120 spins per second,(ideal conditions) but cpu, and gpu's process way more MB/s of data per "hz" if you will.
....what???

Moto is right, you can't compare them at all.

I kind of understand what you are saying though, you mean that they both hit 1 point x amount of times per second.

20. Hehe, I don't quite understand your post but you can't talk about a spinning object in hertz no matter what sort of point of view you look at. It's like asking how many slopes (remember from Algebra, rise over run) does an apple weigh.

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