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Originally Posted by 3eand4i
Uhm about this i just read somewhere about the unefficiency bandwidth while using SATA3 or USB 3 @ P55 motherboards. Pls wait, i'll be back for more information. You must have PLX bridge on the board such as ASUS P7P55D Premium solution.
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Here we go. for SATA 3 and USB 3.0 support mainboard available @ market now we just have full range P55 by Gigabyte and ASUS P55 Premium rev or Asrock with external card for SATA3
Firstly via Gigabyte website mentioned about this disadvantage:
* When dual graphics cards are used in 1st and 2nd PCIex16 slots, SATA3 / USB 3.0 (Marvell 9128 /NEC USB 3.0 Controllers) will work at normal mode.
Basically that mean:
- If you want to use full speed of USB 3.0 or SATA 6Gb/s, you will lose a PCIe 2.0 x16 slot => no SLI/CrossFireX support. Even if you might not be running SLI/Crossfire but when you use EITHER USB 3.0 or SATA 6 Gb/s, your PCIe x16 will only run at degraded model (as low as PCIe X 8 only)
- You can only choose EITHER USB 3.0 or SATA 6 Gb/s to run at full capacity. The board CAN NOT provide these 2 functions at full capacity at the same time.
- If you decides to run Crossfire or SLI, BOTH USB 3.0 and SATA 6.0 Gb/s need to run at degraded mode (250MB/s only compare to their full capacity 600MB/S)
WHY???? Let’s explore this in details:
Gigabyte borrow the PCIe 2.0 lane from CPU to achieve the bandwidth for SATA3 or USB 3.0 so
1. If you want to run SLI/Crossfire, CPU provides PCIe 2.0 x8, x8 to dual PCIe x16 slots.
The USB 3.0 & SATA 6 Gb/s are connected to P55, therefore both of them can only have 250mb/s from PCIe 1.0 (which is 41% of their full capacity).
_hxxp://img43.imageshack.us/img43/4497/10292814.gif
2. When the USB 3.0 is connected.
One PCIe 2.0 x8 lane switches to USB 3.0 => one PCIe x16 slot (@x8 speed) is disabled.
meanwhile the SATA 6Gb/s, since its still connected to P55 at PCIe 1.0, is at degraded Mode (250mb/s only (41%) of its full capacity). Not even to mention, the PCIe x16 slot for VGA is now only running at x8 speed (50% of its full capacity)
_hxxp://img43.imageshack.us/img43/9996/82723426.gif
3. When the SATA 6Gb/s is connected. The “symptom” is the same.
One PCIe 2.0 x8 lane switches to SATA 6.0 Gb/s, hence one PCIe 2.0 x16 slot (@x8 speed) is disabled. and USB 3.0, since its still connected to P55 at PCIe 1.0, is at degraded mode (250mb/s ŕ only 41% of its full capacity). Again, the PCIe 2.0 x16 slot for VGA is now only running at x8 speed (50% of its full capacity).
_hxxp://img43.imageshack.us/img43/2674/87625496.gif[/IMG]
And you must go to BIOS for choosing while SATA3 or USB3.0 @ performance mode. not easy hah lolz
But it's not mean that we can enjoy the fully sata3 and usb3.0 @ p55 motherboard. If you really love those two so you can pay more and go for ASUS P7P55D Premium or another boards have the PLX bridge for SATA3 and USB3.0
ASUS Solution: leave PCI-E 2.0 from CPU 1156 alone (so we still have full 16x 2.0 single VGA or true 8x 8x for dual VGA) and intergrated PLX chip for SATA3 and USB 3.0
_hxxp://img97.imageshack.us/img97/3091/85488057.gif
as we all know, P55 provides PCIe 1.0 x4 lanes to PLX Bridge Chip, and then transformed to PCIe 2.0 speed. So BOTH SATA 6Gb/s & USB 3.0 are connected to the PLX bridge and at their FULL capacity at the all time (benefited from the addtional transformed PCIe 2.0 bandwidth).
Maybe that the reason why Gigabyte annouce about new UD7 series with the same PLX bridge. But we still waitting for real HDD SATA 3 and USB 3.0 for "real" performance testing base on those theories.
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