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SATA Disks


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#1
Gouverneur

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It seems to me that parallel transfers should be faster than serial for disks rotating at the same speed. I think the older IDE disks rotated at the same rate as modern SATA Disks. They used 40 wires. What was transferred via all those wires? I think SATA uses only 7 wires.
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#2
Kemasa

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The transfer rate is what determines the speed. PATA is older and slower and while you could speed it up to be faster than SATA, that is just not the case.

For some thoughts on the matter see:

http://blog.taragana...drives-a-guide/
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#3
Gouverneur

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I am curious about why SATA Disks are faster. All I read is that SATA Disks have a higher data tranfer with no explanation of why.

I expect to buy a new system with SATA Disks because I believe the claims for faster & better technology. I just want to know some details about why is is faster.

Is the data density higher? Do PATA & IDE disks not use most of the 40 wires? Do SATA disks rotate faster? Do PATA & IDE disks collect the data in some buffer & it sits there for a while?

All other things being the same, serial data transfer over fewer wires should be slower than parallel transfer over many Wires. What things are not the same?
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#4
rshaffer61

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The SATA controllers transfer faster then the IDE controllers.
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#5
Gouverneur

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I am well aware of the following.

The SATA controllers transfer faster then the IDE controllers.

The above is essentially what articles & people say & I believe it is true.

However, such statements do not explain why the SATA controllers are faster.

As far as I know, the SATA disks do not rotate faster than PATA/IDE disks. It that is the case, what causes the faster data transfer?

How many bytes per track on SATA & PATA/IDE disks? A big difference in bytes per track or a faster rotation rate or both would go a long way toward explaining the faster transfer rate. The SATA cables have two wires for data transfer in each direction. Do the controllers read from two tracks concurrently?
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#6
Kemasa

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Why is a modern vehicle faster than a Model A? Some of the modern vehicles have a 4 cylinder engine, whereas many older vehicles have bigger engines.

There are several aspects to the speed of a disk. The first is the speed the data can be retrieved from the physical disk, which involves the rotational speed, density, number of heads, etc., but then there is a bottleneck in getting the data from the disk controller to the main memory. This is limited by the disk controller and the data channel. This is where the difference between the PATA and SATA comes in.

You can also have a bottleneck at the disk due to latency, seek delay, etc. The faster speed of SATA may or may not buy you anything due to how you are using the disk.

The speed difference you are talking about is the data transfer speed from the onboard disk controller to the disk controller in the computer. You would have to see if they speeds that are being quoted are actually for reading data and how much data is being read. It is typically the maximum speed possible.
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