LGA1156 mATX board with PLX chip (and some additional questions)

[AndyKH]

Hi

I've been reading up on the bottle neck associated with USB 3 (and SATA 6 Gb/s) on LGA1156 boards.

The PLX chip found on some ATX size boards seems to do a good job working around the bottle neck, but I can't find any mATX boards with such a chip. For a while I though that the ASUS P7H55D-M EVO did include it, but I was proven wrong.

Do any of you know of any presently (or soon to be) available mATX LGA1156 boards with the PLX chip?

Also, on the boards that don't feature the PLX chip, I'm a bit uncertain as to which degree it's possible to choose whether you want to sacrifice 8 lanes for the gfx card or instead sacrifice USB 3/SATA 6 Gb/s performance by letting these interfaces run of the PCH:

Is it correctly understood that ASUS MBs will always sacrifice USB 3/SATA speed when a gfx card is installed, or is it configurable?

Also, is it correctly understood that Gigabyte MBs allow you to choose whether to sacrife gfx speed or USB 3/SATA performance?

It should be added that I have looked in manuals from both ASUS and Gigabyte. I can't find any info about how to choose where to sacrifice performance even though I remember several reviews mentioning something about being able to choose it.


All help will be greatly appreciated

Thanks in advance

 

[coffeejunkee]

P7H55-M/USB3 seems to be the board you're looking for.

Concerning usb3/sata3 implementation:

To my knowledge, Gigabyte is the only brand that uses pci-e 2.0 lanes from the cpu to connect these controllers. They do so to reach the full sata3 600MB/s bandwith. As a result, there are only 8 lanes left for the graphics card. This doesn't impact most midrange cards but high-end cards are affected, although not that much. Exception is the UD7 which does use a plx chip.

On GB mobo's you can choose to run usb3/sata3 in non-turbo mode. In this case the controllers are routed to a single pci-e 1.1 lane from the ich10 southbridge. Max bandwith is 250MB/s which is still a lot compared to usb2 but not really satisfying for sata3, since it's less than sata2. You'll also have to use this configuration when you run cf/sli.

Other brands use the same pci-e 1.1 lanes from the southbridge but use a plx chip to turn 2 lanes into 1, doubling bandwith from 250 to 500MB/s. So not the official sata3 bandwidth but at least it's more than sata2. The advantage being that the graphics lanes are unaffected.

 

[NumericalMethods]

Some models of Asus board, the P7P55D-E for example, have a switch that allow you to change whether you just use the PCH lanes or use some of the CPU PCIe lanes. The feature is called IO Level Up I think. Not sure if they are offering the feature on their smaller boards though.

 

[coffeejunkee]

So that would be almost the same as the Gigabyte method, except for the fact that Asus uses a plx chip to multiplex the pch lanes and GB doesn't. And Asus does in fact offer full sata3 bandwith if needed. Thanks for telling, I didn't know this was possible.

(my guess would be that on the matx boards there's not enough room for the required extra circuitry. Also, Asrock's true333 makes more sense now, I think they use the same method to get 'true' sata3)

 

[NumericalMethods]

Yeah, it's not a bad solution. They don't seem to have implemented it on many boards though. My P7P55D-E Evo doesn't have the option. I'm assuming that it has to do with the way the PCIe lanes are set ie 16x 4x on the P7P55D-E and 16x or 8x 8x for SLI/ Crossfire on the Evo.

I think that it isn't on the matx boards for the circuitry reason or to keep costs down It's weird that Asus haven't advertised it much. There might be a few people who appreciated the feature.

 

[AndyKH]

Thank you all for the replies

I've been

@Coffeejunkie
Does the P7H55-M/USB3 implement a PLX chip? I can't find any information cooperating that (but then again it's seriously hard to find any information on that board - I think it was launched quite recently).
However when rereading the manual for the board I found that it does feature an IO LevelUp switch in the BIOS that allows you to connect either the USB 3 controller or the SATA contoller to a CPU PCIe lane (but unfortunately not both even though there are plenty of lanes available when dropping the gfx card slot to 8x).

In the manual for the P7H55D-M EVO it is stated that using an expansion card will drop the USB 3 speed to "gen 1" speed which I interpret as the MB automatically switching from using CPU PCIe lane(s) to using a lane from the H55 chip. When reading the manual for that board I haven't found anything suggesting that it is possible to switch manually.

I did reread the manuals for the two Gigabyte mATX boards suporting USB 3 and neither of these seems to support switching the USB 3 controller to or from using CPU PCIe lanes. In fact it doesn't mention anything about USB 3 bandwidth being affected by installing a gfx card, so I'm a bit uncertain they are capable of using CPU lanes for the USB 3 controller at all.

It's at times like this that I'm really annoyed that most MB manufacturers are so bad at describing how their boards are implemented.

 

[coffeejunkee]

Yeah, it's not a bad solution. They don't seem to have implemented it on many boards though. My P7P55D-E Evo doesn't have the option. I'm assuming that it has to do with the way the PCIe lanes are set ie 16x 4x on the P7P55D-E and 16x or 8x 8x for SLI/ Crossfire on the Evo.

That sounds logical.

Andy: P7H55D-M EVO doesn't have sata III? Only usb3...and it seems to use a plx chip, at least that's my interpretation: without using an expansion card the plx chip use 2 pci-e lanes from the pch, if you do put in an expansion card 1 of these lanes is used for the card and 1 is left for usb3. Not quite sure though what they mean by 'gen1', since 250MB/s is still a lot more than usb2 can handle.

It's correct that nothing is mentioned about lanes for the usb3 models on the GB site, unlike with their A series boards. I've read a review about the p55-usb3 though, and it clearly stated that this mobo uses either pci-e 2.0 lanes from the cpu or 1 pci-e 1.1 lane from the pch. I'm assuming it's the same for their mATX usb3 boards.

Well, it's not suprising that this information is hard to find. It's much easier for marketing to slap sata3!!! and usb3!!! stickers on the box than to explain complicated stuff like this that will put off their customers. My advice: dont bother with sata3 till it's in the chipset (marvell controller is crappy anyway) and buy an usb3 card if/when needed.

 

[AndyKH]

That sounds logical.

Andy: P7H55D-M EVO doesn't have sata III? Only usb3...and it seems to use a plx chip, at least that's my interpretation: without using an expansion card the plx chip use 2 pci-e lanes from the pch, if you do put in an expansion card 1 of these lanes is used for the card and 1 is left for usb3. Not quite sure though what they mean by 'gen1', since 250MB/s is still a lot more than usb2 can handle.

It's correct that nothing is mentioned about lanes for the usb3 models on the GB site, unlike with their A series boards. I've read a review about the p55-usb3 though, and it clearly stated that this mobo uses either pci-e 2.0 lanes from the cpu or 1 pci-e 1.1 lane from the pch. I'm assuming it's the same for their mATX usb3 boards.

Well, it's not suprising that this information is hard to find. It's much easier for marketing to slap sata3!!! and usb3!!! stickers on the box than to explain complicated stuff like this that will put off their customers. My advice: dont bother with sata3 till it's in the chipset (marvell controller is crappy anyway) and buy an usb3 card if/when needed.

Thanks again

If you can find a link to a review that indicates the presense of an PLX chip on the P7H55D-M EVO board then please post it as I really doubt that there really is an PLX chip on that board.
Also, I know that the EVO board doesn't feature SATA 6 Gb/s but that doesn't really annoy me very much, I'm more interested in USB 3.

The way I interpret text about "gen 1" is that it reverts to using 1 "gen 1"/half speed lane from the PCH if a gfx card is installed - otherwise it uses a CPU PCIe lane. Also, If the board used a PLX chip, then I can't see why adding an expansion card to one of the 1x slots cause any changes: H55 supports 6 PCIe lanes, two of which would be used by a PLX chip and 4 being available to the 2 1x slots.

Is it also you impression that the P7H55-M/USB boards implements a PLX chip?

 

[coffeejunkee]

Ah, that makes more sense: gen 1 refers to a pci-e 1.1 lane. So that would mean that the P7H55D-M EVO uses the same implementation as Gigabyte, without a plx chip. Except Gigabyte is nice enough to actually mention something about this on their website. I think it's safe to assume the P7H55-M/USB3 uses the same implementation.

The review I read was about P55 sata3/usb3 boards, and it was mentioned that all manufacturers except Gigabyte use a plx chip. But apparently Asus chose to do it different on their H55/H57 boards (saves plx chip costs). Sorry for getting your hopes up. It still shouldn't bother you that much, 250MB/s is plenty for an external hdd (or do you have special usb3 needs?)