why sata(serial ATA) is faster than pata(parallel ATA) ,however Parallel access of data is faster than serial?

Question

why sata(serial ATA) is faster than pata(parallel ATA) ,however Parallel access of data is faster than serial?

Answer 1

parrallel is not faster.

your pata transfers at 66MB/s

sata1 is 1.5Gb/s or 188MB/s

sata2 is 3.0Gb/s or 375MB/s

so you tell me. i have 2 sata1 hdd's on raid0

Installed XP in 12 minutes! (unattended)

Answer 2

Hi there.



This is a very nice question and logically what you are saying should be correct. However, there is a reason behind this.



In serial connection, there are two lines, one for data and other for acknowledgement. In parellel there are eight. Logically parellel should be faster. But it is the other way, i.e. serial ata is faster.



Let me explain you this using an example i read once.



Consider a two lane highway, similar to serial ata, having one lane to transferring data cars and other meant for acknowledgement. Similarly an eight lane highway for parellel ata.



Now since data flows in one direction at a time, when sata is used, data is sent across the lane. Immediately after that an acknowledgement is sent thru the ACK line and only then the second shift of data is transferred. Meaning it is only after the data ack arrives, the other shift of data is sent.



Now in case of parellel ata, you have eight lanes. When data is sent across these 8 lanes, you will need to synchornise the data received from these 8 lanes at the other end and it is only after this that the ACK is sent. Therefore suppose there is an error in any of the 8 lanes(or data lines actually) you will need to request the data again.



Obviously there is high probabilty of error in 8 lanes than a single lane as in case of serial ata. Managing eight lanes is much much more time consuming than managing a single lane bcoz u dnt need to synchronise the data everytime.



Therefore problem of syncronization is the real reason that PATA is slower than SATA.



I hope you got the point.



-k-

Answer 3

The reason SATA is faster IS the fact that it’s a serial connection.



With a serial connection, you’ve only got one data line and one acknowledgment line to worry about. Think of it as a two-lane road where half the road is closed and you’ve got “stop-go” signalling working to get cars going in both directions.



Imagine a “data” car has been sent down the road. Once it reaches the other end of the roadworks, an acknowledgement (ACK) car is sent back the other way. The ACK car isn’t sent until the first data car arrives and the second data car can’t leave until the first ACK car arrives at the other end.(In practice, data and ACK signals are sent down separate lines but the principle is the same.)



Now for PATA, you have the extra problem of synchronisation – that’s a big fancy word that means data sent down all eight lines has to reach the destination at the same time before it can be correctly registered and an ACK signal sent back to say “yep, got that – send down the next eight.”



The problem is at 150 MHz, you’re talking about nanoseconds of time trying to get those data lines all sync’d up at the same time and the drive manufacturers say that’s too difficult to do beyond 150 MHz.



In other words, the drive controller has to wait until data on all eight lanes has been correctly set before it can say it’s got a byte of data.And at these speeds, that’s far easier to do when you’re just worrying about one lane rather than eight.

Answer 4

While on the surface it may seem that accessing 8-bits of data at once compared to a bit at a time would have speed advantage, recent technology has focused on improving serial transfer speeds using specialized chips. The difficulty with parallel transfer of data is the need to keep all of the bits synchronized so that the full byte (8-bit) value can be realized. This synchronization requirement complicates the process and eventually causes a bottle-neck. Even such tried-and-true parallel methods (SCSI interface) are being replaced with serial versions (iSCSI) which uses serial transmission of data rather than parallel.

Answer 5

because SATA is faster