SATA 6 Gbps: The Right and the Wrong Way Options

[Zertz]

With the recent and upcoming release of drives utilizing the latest SATA 6 Gbps interface, manufacturers are rushing out motherboards to support the new standard. Since the P55 chipset, or any other for that matter, only support up to SATA 3 Gbps so companies have to resort to a third party controller. The only one being used, that I know of at least, is the Marvell SE9123. Using a single PCI-Express 2.0 lane (500 MB/s in both directions), it supplies two ports, but no RAID.

You probably noticed the potential bottleneck here, third generation SATA can provide bandwidth up to 600 MB/s, while the PCI-E lane will only do 500 MB/s. Well, that’s hardly a problem considering even the fastest SSDs aren’t reaching those speeds, for now at least. Anyway, I’m heading off course.
For some reason, Intel only gifted the P55 chipset with PCI-Express 1.0 lanes (250 MB/s in both directions) and there lies the issue. For a SATA 3 Gbps controller, it’s not too bad, but for a next generation controller, it causes a major bottleneck. There are two ways around this; one of them being quite obviously the better solution.

The easy, scratch that, wrong way is to take PCI-E 2.0 lanes off the processor and feed them directly to a SATA 6 Gbps (and USB 3.0) controller. However, there is a major downside. Remember that Lynnfield only has 16 lanes and you need 8 of them for a graphics card. Once these two controllers are enabled, you’re left with 14 lanes and the hardware is only designed to give 8 of them to the graphics card so you’re essentially wasting the remaining ones. The ugly part is that you lose CrossFire and/or SLI since the second slot can’t live off 6 lanes.

Then there’s the other way - the right way. It involves a PLX chip, similar to what ATI uses on dual-GPU cards. Its job is relatively simple, take 4 PCI-E 1.0 lanes and turn them into a pair of PCI-E 2.0 lanes. Simple enough. It’s just as fast as the other implementation, bare a few nanoseconds of latency, while retaining CrossFire and/or SLI capabilities. With the remaining 4 PCI-E 1.0 lanes, you can still have two PCI-E 1x slots, a PATA/SATA 3 Gbps controller and whatever else you can think of.

I’m not naming anyone, but you should be able to figure it out fairly easily

[Guest_Digitalis_*]

First; HDDs with 6GB/sec are not performing any better than current top HDDs; so, they do not need this SATA "3".

Two Intel SSD's in Raid 0 hit till 500Gb/sec in read and you do not need SATA 3.

If you need sata 3 than there is the Asus 920 motherboard with two N200 chips added.

This post has been edited by Digitalis: Nov 7 2009, 12:54 PM

[Zertz]

First; HDDs with 6GB/sec are not performing any better than current top HDDs; so, they do not need this SATA "3".

Two Intel SSD's in Raid 0 hit till 500Gb/sec in read and you do not need SATA 3.

If you need sata 3 than there is the Asus 920 motherboard with two N200 chips added.

Your first "fact" is wrong. GB/sec != Gbps and nobody claimed HDDs need SATA 6 Gbps.
Your second "fact" is also wrong, I suggest you look up bit and bytes.
And I'm waiting on a link for your third "fact".

Like Smithy mentioned... NF200 just moves the bottleneck from the processor or chipset to NVIDIA's chip, there's nothing to gain with this chip.

This post has been edited by Zertz: Nov 9 2009, 08:26 AM