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I just bought a new pc. It has a 1.5TB harddrive made by Seagate, the ST31500541AS. This harddrive has a rotation speed of 5900RPM and a cache memory of 32mb.

Now, my old harddrive is a 500GB Western Digital, the WDC WD5000AAJS-00TKA0 (It's a caviar blue drive, if I'm correct). This harddrive a lot smaller in size and has a smaller cache memory of 16mb. The drive is spinning at 7200RPM, though.

The question is, which has the bigger importance? Is a drive it's performance more depending of cache memory or on rotations per minute? I also have a 2nd questions which is: which drive is better for carrying my operating system, games and office programs, and which is better for carrying all my pictures, music and movies?

asked Oct 25 '11 at 10:47

Mitte's gravatar image


Nowadays the cache is used differently than say 5-10years ago. Because HDDs are so large the file table need cache to operate properly which is why you typically only see 64MB on 2TB+ drives. The difference between 16 and 32MB cache is negligible however the speed is not. 5900RPM is a somewhat odd speed, usually it's 5400, 7200 and 10000. What the speed improves above all is the access time. I know that 5400 HDDs usually have an access time of about 13 seconds while a 7200 has about 9ms. This is based heavily on your degree of fragmentation because every time the head needs to read a file that is chopped up it needs to read one part of the file, return to the file table to find the next part, go to that part, read it and if it's chopped up even more it has to return to the file table again. This is where SSDs really shine because not only is the access time about 100x faster but it can read the file table at the same time as the file itself effectively eliminating the access time. (BTW if you didn't know, the file table is what occupies the space that gets reduced when you format the drive. It's basically an excel spreadhseet where the location of every file is on the drive.

Another thing that improves with RPM is the read/write speeds. A good 7200RPM drive will read and write at about 100MB/s depending largely on your fragmentation. A 5400RPM decreases that to about 70MB/s for most drives.

If I were you I'd install it on the newest drive, even if it's slower speed it's more reliable and might contain new technologies that like NCQ etc.

answered Oct 27 '11 at 10:11

Yarvaxea's gravatar image


definitely more rpm. if your processor is fast enough and your cache is at least decent it'll be fine. i don't know if your describing it right though. there is no cache on your hard drive. the cache is sram located directly on the processor. very far away from the hard drive.

answered Oct 28 '11 at 06:36

GilOsborne's gravatar image



HDDs have cache in the same manner as CPUs have cache. They are not used entirely in the same way though. Both will speed up the device in certain circumstances, but almost always a higher RPM or a higher clockspeed will give more performance than cache memory.

(Oct 28 '11 at 11:21) Yarvaxea Yarvaxea's gravatar image
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Asked: Oct 25 '11 at 10:47

Seen: 1,535 times

Last updated: Oct 28 '11 at 11:21