Member Avatar for mahela007

I was just reading about the different types of cables used to connect components of computers. When it comes to serial ports and parallel ports, parallel ports are faster because they send several bits of data simultaneously. Therefore, it should follow that parallel ATA is faster than Serial ATA. However, that's not the case. Why is this?

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Member Avatar for jbennet

Its more extensible. Most of the wires in an old style ATA connector dont actually help transmit data, they are to stop interference (they actualy doubled the number of wires to 80 by adding more grounds). SATA however, has a higher cieling for this so just uses two pairs of wires for a total of 4 (with 3 grounds). This means its got a reduced cost and is easier to route as its smaller and allows for 3-6gb speeds under the current commn SATA specs. SATA also uses twisted pairs and differential signalling (sending the inverse of each signal to compliment eachother and reduce interference in much the same way as noise cancelling headphones do) which reduce interference and keep data rates up.

SCSI is technically faster, but its more expensive to implement due to its architechture.

Edited by jbennet because: n/a
commented: Was searching for this reason since long. Found a thread. Nice reply !! +0
Member Avatar for mahela007

Isn't SCSI deprecated?

Member Avatar for zortec

No, it is not deprecated yet but it will be soon now that SATA-2 has taken over.

Member Avatar for jbennet

No, it is not deprecated yet but it will be soon now that SATA-2 has taken over.

No, it will be superceded by SAS if anything.

Member Avatar for nileshgr

Its more extensible. Most of the wires in an old style ATA connector dont actually help transmit data, they are to stop interference (they actualy doubled the number of wires to 80 by adding more grounds). SATA however, has a higher cieling for this so just uses two pairs of wires for a total of 4 (with 3 grounds). This means its got a reduced cost and is easier to route as its smaller and allows for 3-6gb speeds under the current commn SATA specs. SATA also uses twisted pairs and differential signalling (sending the inverse of each signal to compliment eachother and reduce interference in much the same way as noise cancelling headphones do) which reduce interference and keep data rates up.

SCSI is technically faster, but its more expensive to implement due to its architechture.

Thanks for this great info.

Edited by nileshgr because: n/a
Member Avatar for mahela007

yes.. Thanks for the gread info but I don't think you answered my original question.
Why is SATA faster? (Every bit has to be sent one behind the other)

Member Avatar for jbennet

yes.. Thanks for the gread info but I don't think you answered my original question.
Why is SATA faster? (Every bit has to be sent one behind the other)

Because there is less electrical interference when you send things in serial fast in one direction at a time over a lower set of wires than when you send things in parallel over more wires (as in the case with PATA). PATA should in theory be faster but it isn't due to this limitation.

Its just like with network cables. To achieve gigabit speeds the cables have much more shielding to prevent crosstalk (which reduces bandwidth)

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