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SATA III PCIe Card

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Hey gang,

I was just curious and am having trouble finding definitive information on this. I'm going to be purchasing an SSD in the near future (Vertex 3 :D  ) but I have a slight dilemma... I kind of overspent on my almost fully updated build and cheaped out on my mobo, I got a GA-X58-USB3 which does not have onboard SATA III, so I will need to purchase a PCIe card to handle the drive, (Possibly a raid controller, but that won't be happening in the near future, so for now just a card with a couple of ports). I have heard speculation about cards that operate on a PCIe x1 interface not being able to utilize the full bandwidth of SATA III, I would like some closure on this. Because reason A...: Why would a card that operates on x1 for the soul purpose of enabling SATA III exist if it can't utilize the bandwidth since SATA III is backwards compatible with SATA II, that just defeats the purpose. And reason B....: I read this in a couple newegg reviews, which, lets face it... are written by hapless techno-wienies half of the time and should generally be taken with a grain of salt. But still, my anal retentive self just wants to make sure. Any help on this or recommendations for the card would be much appreciated. Thanks in advance

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SATA 6Gb/s has a maximum speed of 6 gigabits per second which is about 750 megabytes per second. PCIe 2.0 specifies 500 megabytes per second on each lane. Hence a PCIe 2.0 x1 slot has a maximum speed of 500 megabytes per second (an x8 slot would have a speed of 500*8 = 4000 megabytes per second). Thus an x1 slot will inhibit the speed of a SATA 6Gb/s port. That being said, your average SATA 6Gb/s SSD maxes out at about 500 megabytes per second, so if you have one SATA 6Gb/s drive on a PCIe x1 controller then your speed won't be inhibited too much (and it will be faster than a motherboard's SATA 3Gb/s port). However if you put two SSD's on a single PCIe x1 controller then the transfer speeds will likely be inhibited.

It's hard to find a good SATA expansion card for a reasonable price.
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o00JONESY00o said:
I have heard speculation about cards that operate on a PCIe x1 interface not being able to utilize the full bandwidth of SATA III, I would like some closure on this. Because reason A...: Why would a card that operates on x1 for the soul purpose of enabling SATA III exist if it can't utilize the bandwidth since SATA III is backwards compatible with SATA II, that just defeats the purpose.


The maximum data transfer rate of a SATA II port is 300 MB/s.
So any Read/Write speed from 301 MB/s to 600 MB/s is considered SATA III speed.

SATA III PCIe x1 cards were originally to RAID HDDs and for 1st generation SSDs.
We are now on 3rd gen SSDs and these cards cannot keep up with the advances in technology.

So if you purchase a SATA III PCIe x1 card to use with your Vertex 3 expect around 400 MB/s Read and 300 MB/s Write speeds.
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Thanks so much guys. Forgot about the 500MB/s cap per lane. Hadn't even thought about lane speed since PCIe 2.0 came out. Oh boy, it is sad when all of your schooling for programming takes over your hardware love. Again, thanks a lot guys.

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Honestly, a PCIe x1 SATA controller for a single SSD won't be a serious bottleneck. An x4 controller will cost $100 for a minimal performance improvement that will be noticeable only when you run benchmarks.

Yeah, I was thinking the same. I'll just get the vertex three and an x1 controller for like 40 bucks until I get a new mobo. I remember when I thought my two 7200.12s were hot stuff in raid 0, then I got an SSD for my lappy and now the world is upside down. Haha.

o00JONESY00o said:
I have heard speculation about cards that operate on a PCIe x1 interface not being able to utilize the full bandwidth of SATA III

Like you, I recently purchased a fast SSD (Corsair Force GT) even though I only have Sata-II ports on my MoBo (also Gigabyte with PCIe 2.0 slots).

I've been running my GT via the onboard Sata-II ports but wanted to take advantage of full Sata-3 speeds, so I purchased as ASMedia ASM1061 PCIe x1 Sata-III card.

My Read speeds increased by as much as 35% (from 275MB/s to 405MB/s), but (for reasons I have yet to determine), my Write speeds fell though the floor (by as much as 80%). Slower than even a standard HDD, slower than I was getting using my Sata-II ports. I have no clue why.

Setting the MoBo BIOS to AHCI mode actually made things WORSE. The card has its own "AHCI mode", so I've left my MoBo's Sata ports in "IDE Mode" (via BIOS) and let the card use its own AHCI mode (no way to disable it.)

I have no idea why my Write speeds are so bad. Everything I've read on line says I "should" see write speeds near equal to my read speeds using an x1 card, but I haven't seen "confirmation" anywhere that that is what people are actually getting.

So all I can say is "Beware", Sata-III on a x1 card naturally won't be as fast as onboard Sata-III ports (500MB/s theoretical max on a x1 card vs 750MB/s max onboard), but there may be other technical bottlenecks that I can't explain when using a card for SSD I/O vs onboard ports.
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