Why have SATAs replaced PATAs these days?

4

It seems to me that the general trend in computers is going towards parallel architectures wherever you go. But I've noticed that the term 'SATA' appears much more often than 'PATA' these days...

Isn't the 'P' in PATA supposed to represent the word "parallel" whereas the 'S' in SATA is "serial"? But in the computer world, we are now moving toward multiple processors, cores, etc.

So just wondering why we have been seeing SATA become more popular than PATA (or in other words, why serial has become dominating over parallel).

Dark Templar

Posted 2011-10-09T20:54:22.627

Reputation: 2 329

1

What technologies have you seen that make you think parallel communication is the trend? Some of the most common technologies are serial based. Examples, USB , PCI Express, Ethernet, SAS, and more

– Zoredache – 2011-10-09T22:14:30.077

Answers

8

In it's most basic form (and there are a lot more factors than this one) this is happening because in the PATA system all of the lines must have the data show up at the same time for the data to be readable. If you switch to serial you can increase the frequency by a factor much higher than the highest stable frequency you can get in a PATA system * the number of lines being transferred.

Here is a fairly old article, but relevant to your question, that goes in to more detail. Some things are wrong today (SSD had not become mainstream when this was written so he says nothing can saturate the bus) but the underlying reasoning is still there.

Scott Chamberlain

Posted 2011-10-09T20:54:22.627

Reputation: 28 923

2+1 I can add that the inefficient and risky thing you mentioned ("all of the lines must have the data show up at the same time") affects any parallel bus and it is the exact reason why "long" parallel buses are being replaced by serial ones. The "short" buses can still take some advantage from parallelism. – gd1 – 2011-10-09T21:32:29.707

2Also the crosstalk in the ribbon cable becomes intolerable when the frequency increases. They have to introduce 40 ground wires in the cable just to decouple the data wires. In SATA, differential signaling, which uses more wires, can be used to give a much more reliable signal because the total number of wires is reduced for a serial link. – billc.cn – 2011-10-09T22:14:09.110

1@gd1 Or they use serial lanes in parallel, for example the PCI-Express x16 port you plug your video card is 16 serial connections run in parallel to increase the bandwidth to the video card. Each connection carries it's own clock signal so you don't need to have the precise timing that parallel requires. – Scott Chamberlain – 2013-02-05T08:17:40.860

Asked: 2011-10-09T20:54:22.627

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Active: 2013-02-03T12:33:05.617