What is Serial ATA?

[WheelsCSM]

I have heard about the new serial ATA interface, and I'm just wondering what is new/better about it. I think I saw somewhere that it will have 1.5 GB/sec transfer rate. Is this true? Thanks for any info.

 

[BKnight]

I think you may be confusing parallel ATA with serial ATA. Basically, you are using parallel ATA in your system now. The ribbon cable that connects to your motherboard is a parallel ribbon cable... meaning there are multiple wires running parallel to each other. With serial ATA, you will use a single wire to connect your hard drive to the motherboard... much the same as you use now to connect your CD-ROM to your Sound Card internally.

 

[BKnight]

oh, and to answer your question... serial ATA scales much better and will be introduced with a 600 Mb/s throughput. Correct me if I am wrong on this one please.

 

[Shooters]

I believe serial ATA will also eliminate the need for the whole master/slave thing.

 

[ViRGE]

Forget the maser/slave thing, I just want the thin cables.

 

[ugh]

<< Forget the maser/slave thing, I just want the thin cables. >>


I second that! I can't bear to see the amount of tangled wires in my casing

 

[AndyHui]

I have a little bit about Serial ATA in the FAQ here.

 

[Insane3D]

Wow...great info Andy!

 

[Bozo Galora]

anand has pics on todays "day 2 IDF" article.

 

[Insane3D]

Holy sh*t! Look at that four way Xeon board! :Q:Q:Q

 

[SCSIRAID]

Serial ATA transfer rate on the wire is 1.5 Gigabits per second. After subtracting the encoding overhead it boils down to 150 Megabytes per second max data rate. Two 'follow ons' generations are described in the spec with wire rates of 3 and 6 Gbit

It is a point to point interface with only one drive per cable. Max length is 1 meter. Its a 7 wire cable - 2 twisted pairs plus 3 grounds.

Should appear next year as specialty products with high volume in 2003.


EDIT: Thorin posted a bunch of links in another SATA thread to loads of info..

 

[thorin]

SCSIRAID
"EDIT: Thorin posted a bunch of links in another SATA thread to loads of info.. "

Yup it's right over here>

http://forums.anandtech.com/messageview.cfm?catid=27&threadid=547466

WheelsCSM
"1.5 GB/sec transfer rate."

Actually it's 1.5Gigabit (not GigaByte) and uses 10b encoding (8bits data + 2bits error correction). Thus 1.5Gb / 10b = 150MB

Thorin

 

[volfan]

Well, I'm not an expert, but...isn't there a new ATA-133 standard coming out to increase the now-standard ATA-100? So really we will only be going from 133 to 150 MB/sec. Also, aren't the max sustained data transfer rates not even really reaching the ATA-66? If this is the case why do we keep increasing the pipe if we haven't even been filling the one we have? Seems like they need to start figuring out how to get the hard drives to transfer data more quickly. Am I right?

 

[SCSIRAID]

Thorin:

"Actually it's 1.5Gigabit (not GigaByte) and uses 10b encoding (8bits data + 2bits error correction). Thus 1.5Gb / 10b = 150MB"


The two extra bits arent for error correction. They are part of the encoding algorithm that insures that a) the link is DC balanced and b) that there are signal transitions to keep the PLL in sync. Imagine transferring a string of "00"'s.. No transitions are occuring and the PLL has no reference to stay in sync.

 

[SCSIRAID]

Volfan, The increase in the pipe is not the 'meat' of SATA IMHO. It is the tiny little cable that can be 1M long and the ability to hotswap.

 

[thorin]

SCSIRAID
"The two extra bits arent for error correction. They are part of the encoding algorithm that insures that a) the link is DC balanced and b) that there are signal transitions to keep the PLL in sync. Imagine
transferring a string of "00"'s.. No transitions are occuring and the PLL has no reference to stay in sync. "

Sorry my bad. Would "flow control" or "signaling bits" be a better statement?

volfan
"Well, I'm not an expert, but...isn't there a new ATA-133 standard coming out to increase the now-standard ATA-100? So really we will only be going from 133 to 150 MB/sec. Also, aren't the max sustained data transfer rates not even really reaching the ATA-66? If this is the case why do we keep increasing the pipe if we haven't even been filling the one we have? Seems like they need to start figuring out how to get the hard drives to transfer data more quickly. Am I right? "

Yes ATA133 standard was just released/implemented. Yes the max sustained transfer rate of the best IDE drive on the market is only 37.5MB/Sec (barely above ATA33, barely giving a reason for ATA66). However with ParallelATA (ATA33 to ATA133) only one drive is using that bandwidth at a time. With SerialATA multiple drives can be using that 150MB/Sec at the same time.

Thorin

 

[SCSIRAID]

Thorin,

They are really just encoding overhead much like MFM was in the old days.... They are not flow control or signalling bits. In fact you cant really look at them as 'two extra bits' in addition to the 8 data bits. 8B/10B maps an 8 bit data byte into a 10 bit transmission character. For example the byte "3F" would be represented as "XX" if the previous byte left the encoding in "positive running disparity" or as "YY" if negative running disparity. Disparity is an indications of whether the transmission needs more 0's or 1's to be DC balanced.

yy = 101011 1001
xx= 010100 1001

There is an error detection (but not correction) aspect to this as disparity errors can detect some bit flips but not bulletproof.

 

[volfan]

Thanks for clearing that up, Thorin. I wonder what would be a good real-world example of needing higher simultaneous transfer rates for multiple drives? I'm just wondering if this will be such a great thing presently or a good standard for future technologies. And I do hear what your saying about cable length and size.

 

[thorin]

" I wonder what would be a good real-world example of needing higher simultaneous transfer rates for multiple drives? "

SCSI does this already. SerialATA is definately not a SCSI replacement however it does bring IDE/ATA performance closer to SCSI. This will allow improvements in:

1) CD Burning.
2) Video Editing.
3) Image manipulate where large temp files are created.
4) Faster OS Swap/VM.
5) Etc...

Thorin

 

[Insane3D]

Bah...I'm interested just for the smaller cables...hehe.

 

[ScrapSilicon]

...bump this.... I want an inexpensive ram drive...pfaugh on spinning mechanical platters