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Which P55? UD3R OR UD4P

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December 9, 2009 2:42:10 PM

just a quick question guys. I've been searching around for a mid cost P55 motherboard and have came across the P55-UD3R and UD4P. Now I only plan to use 1 gpu which makes the ud3r more reasonable because of the 1 x16 slot. I also hope to overclock a core i5 to at least 3.6 ghz. Am I missing out on anything that the UD4P has and the UD3R doesn't considering the UD4P is 50 dollars more?

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December 9, 2009 6:04:47 PM

I hear that the new P55A's have problems while using the new usb and sata 3.0. Is this true?

I remember reading somewhere that when using sata/usb 3.0 the pci express lanes went from x8 down to x4. I think this is only when using xfire/sli though. And i'll be only using 1 card so hopefully it's just a xfire/sli issue. Can anyone correct me on this?

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December 9, 2009 6:45:36 PM

i read from gigabyte taiwan's website that the FIRST pcie slot goes from 16x to 8x when using sata3/usb3 . thats not good , even in single graphics .

when using dual x8 graphics in ud4 and above , the sata 3 and usb 3 work in sata 2 and usb 2 mode (normal ports , no advantage ) .

this info is there in specification page in red color at bottom , but beware , its not given in gigabyte america website !!
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December 9, 2009 7:06:22 PM

I don't know about problems, per se (but, like all new hardware, I'm sure there will be some - there always are...), but the issue is that PCIe bus lane width is a 'zero-sum' game; the only way to get the sorts of speeds that SATA3 and USB3 are promising is to attach to the PCIe bus, and since the PCIe controller, in addition to the memory controller, is on the CPU die, there are a finite number of 'lanes' to hand out - you either 'uses 'em up here' or 'uses 'em up there', but when they're all handed out, they're all handed out! This is the essential difference between Intel's "P" (P31/35/45 etc.) and "X" (X38/48 etc.) chipsets; the Ps are like a scalpel - they have much finer overclocking control, right down to individual memory channel (and, for some, individual DIMM) timing offsets, but are more limited in overall PCIe lane width; the Xs are like a chainsaw - they have more lanes, but are cruder and pretty much 'brute force' overclockers... Another point to be aware of is that, at least at this point, Marvell has not released so much as a RAID BIOS for their SATA3 chips, much less individual system RAID drivers...
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December 9, 2009 7:12:51 PM

thanks billbat , i didnt know that bios thing , and lovely comparison and analogy of p and x series chipsets .
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December 17, 2009 5:20:39 AM

so for now, if one uses a single GPU, you could use a PCI-E x16 card with USB3.0 and SATA3 on the remaining PCI-E x16 lane, avoiding the bottleneck that way. This only works if you have one GPU obviously (i think...)
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December 19, 2009 2:16:37 AM

I just received my P55A-UD4P and have been doing some research on this issue while waiting for my CPU and RAM. This is what the manual says:

Quote:
Turbo SATA3 / USB3.0 (Marvell 9128 /NEC USB 3.0 Controller)
Determines whether to set the PCIe speed of the Marvell 9128 or NEC USB 3.0 controller to PCIe Gen 2. Please note that when only one graphics card is installed on the PCIEX16 slot, it will operate at up to x8 mode if either one of the two controllers is set to PCIe Gen 2. The two controllers will be automatically set to PCIe Gen 1 when two graphics cards are installed on the PCIEX16 and PCIEX8 slots.

Auto: Lets the BIOS automatically confgure this setting, depending on the device installed. (Default)

Turbo SATA3: Sets the PCIe speed of the Marvell 9128 controller to PCIe Gen 2.

Turbo USB3.0: Sets the PCIe speed of the NEC USB 3.0 controller to PCIe Gen 2.

Disabled: Disabled forces the Marvell 9128 and NEC USB 3.0 controllers to PCIe Gen 1.


So it seems like only one of the three interfaces will be able to run at full speed, even with just a single graphics card. It will be some time though until some USB 3.0 and SATA 6Gb/s devices are available to see what the performance impact is between PCIe Gen1 and Gen2.
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