Conclusion: PLX 8747 and Multi-GPU Setups

Any modern day computer that uses more than two PCIe devices is considered a niche category.  For the most part, we have users with a single GPU, then a mix with add-in audio cards, and dual GPUs.  When we hit three GPUs, we are technically in a niche category to which the rich and wealthy are welcome.  Despite this, from talks with ASUS, despite the fact that a product may be geared towards a niche market, that product may sell well to the standard market if it is perceived to be good.

Focusing on Z77 and Ivy Bridge, the default setup for Ivy Bridge allows a three way PCIe 3.0 GPU setup, with the lanes adjusted into x8/x4/x4 layout (or various crippled configurations if the chipset lanes PCIe 2.0 are used).  This is the only way to arrange the lanes from the CPU.  In order to do more with the package, we need a switch – specifically, we turn to the PLX PEX 8747.

In the simplest way of describing the PEX 8747 chip, it allows motherboard manufacturers to direct PCIe 3.0 lanes however they want to the slots.  This chip takes either eight or sixteen of the CPU PCIe lanes and with come clever electronic magic (we believe a FIFO multiplexer) manages to give access to 32.  These 32 lanes can be distributed as they wish, and offer a large array of different configurations in a Z77 motherboard.  It is these configurations that determine efficiency, power usage and performance.  It is also up to the motherboard manufacturers to decide which layout they wish to use.

The one downside is the cost of the chip.  When I reviewed the ASUS P8Z77-V Premium, I speculated that this chip costs in the region of $40.  Since that review, one of our readers got in contact and shared with me the pricing his company gets from their distributor:

Many thanks to Krunal Desai

Thus for a batch of 500 or more of these chips, pricing is in the region of $85 each, which does not include implementation.  After some back and forth discussion with Krunal, we came to the conclusion that it was obvious that the motherboard manufacturers were not paying these amounts – they likely had some distribution deal with PLX as these chips are likely to be around for a long while until PCIe 4.0.  To add more to this, when publishing the ASUS Premium review, I did speak with ASUS regarding my suggested costs of each of the components on that board and they did not blink when I suggested $40 for the PLX chip.  Had they been paying more, it would have been pointed out to me to emphasize the value of the board.  Thus I would expect $40 to be a reasonable amount for large manufacturers (based on my testing of the boards in this roundup, ECS may be paying more than most for the chip).

If a manufacturer wanted to be totally nuts, they could implement two on a motherboard.  Actually, ASRock have done that, on their X79 Extreme11 – the two PLX chips fund an x16/x16/x16/x16 PCIe slot layout with an LSI SAS RAID chip onboard.  We are in the processes of testing and reviewing this board!

To summarize the PLX PEX 8747 usage on the current motherboard scene: the chip itself allows manufacturers to work magic with PCIe layout and lane allocation, especially when the market niche is crying out for better layouts and more bandwidth.  For the regular gamut of single GPU users who require little more than a NIC, some USB devices and a SATA drive or two, there is no need to reach higher than $210 to get all you need.  But going for a PLX PEX 8747 motherboard brings with it a variety of extra functionality alongside the PLX chip in order for motherboard manufacturers to make the distinctions between PLX and non-PLX.

From this review, out of the four motherboards tested, there really is only one motherboard that can take home any sort of prize.  The Gigabyte G1.Sniper 3 is a well built product and a great start to a PLX PEX 8747 focused build. 

The following table represents a quick comparison guide to the four boards tested today, as well as the ASUS P8Z77-V Premium reviewed previously.

Board Comparison Chart
P8Z77-V Premium
G1.Sniper 3
Z77 Extreme9
Price $450 $280 $350 $310 $310
NIC Intel 82579V
Intel 82583
Killer E2200
BCM57781 x 2
Realtek 8111E Marvell
88E8057 x 2
Teaming - No Yes No -
Audio Realtek ALC898 CA0132 Realtek ALC898 Realtek ALC892 Realtek ALC889
VGA No Yes No Yes No
DVI-D No Yes No No No
HDMI Yes Yes Yes Yes No
DisplayPort Yes Yes No No Mini
Thunderbolt Yes No No No No
WiFi Yes Yes (PCIe) Yes (PCIe) Yes No
SATA Controllers Marvell 9320 Marvell 9172 ASMedia ASM1061 ASMedia ASM1061 Marvell 9182
SATA 6 Gbps 6 + 2 eSATA 6 6 4 + 2 eSATA 4
SATA 3 Gbps 3 + 1 mSATA 3/4 + 1 mSATA 4 2 + 1 mSATA 4 + 2 eSATA
USB 3 Controllers ASMedia VIA VL810 Etron EJ188 Texas Instruments ASMedia ASM1042
USB 3 + 2 6 + 6 10 + 4 12 + 8 6 + 6 6 + 10
mSATA SSD 32GB LiteOn No - No -
Fan Headers 6 5 7 3 5
Warranty (NA) 3 Years 3 Years 3 Years 3 Years 3 Years


Conclusion: EVGA Z77 FTW
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  • ultimatex - Wednesday, August 22, 2012 - link

    I got this MOBO from Newegg the first day they had it available , I couldn't believe the price since it offered 8x8x8x8x , Picked it up the first day and havent looked back. Doesnt look as cool as the Asrock extreme9 but it still looks good. Awesome Job Gygabyte , Anandtech should have given them a Gold not bronze though since the fan issue is a minor issue.
  • Arbie - Wednesday, August 22, 2012 - link

    For gaming, at least, how many people are really going to build a 2xGPU system? Let alone 3x or 4x. The are so few PC games that can use anything more than one strong card AND are worth playing for more than 10 minutes. I actually don't know of any such games, but tastes differ. And some folks will have multi-monitor setups, and possibly need two cards. But overall I'd think the target audience for these mobos is extremely small.

    Maybe for scientific computing?
  • Belard - Wednesday, August 22, 2012 - link

    Yep.... considering that most AAA PC games are just ports from consoles... having 3-4 GPUs is pointless. The returns get worse after the first 2 cards.

    Only those with 2~6 monitors can benefit with 2-3 cards.

    Also, even $80 Gigabyte boards will do 8x x 8x SLI/CF just fine.

    But hey, someone wants to spend $300 on a board... more power to them.
  • cmdrdredd - Wednesday, August 22, 2012 - link

    "Only those with 2~6 monitors can benefit with 2-3 cards."

    Oh really? 2560x1440 on a single card is garbage in my view. I am not happy with 50fps average.
  • rarson - Wednesday, August 22, 2012 - link

    If you're going multi-GPU on a single monitor, you're wasting money.
  • Sabresiberian - Wednesday, August 22, 2012 - link

    Because everyone should build to your standards, O god of all things computer.

    Do some reading; get a clue.
  • Steveymoo - Thursday, August 23, 2012 - link


    If you have a 120hz monitor, 2 GPUs make a tonne of difference. Before you come back with a "no one can see 120hz" jibe. That is also incorrect.... My eyes have orgasms every once in a while when you get those ultra detail 100+ fps moments in battlefield, that look great!
  • von Krupp - Friday, August 24, 2012 - link

    No. Metro 2033 is not happy at 2560x1440 with just a single HD 7970, and neither are Battlefield 3 or Crysis. The Total War series also crawls at maximum settings.

    I bought the U2711 specifically to take advantage of two cards (and for accurate colours, mind you). I have a distaste for multi-monitor gaming and will continue to have such as long as they keep making bezels on monitors.

    So please, don't go claiming that multi-card is useless on a single monitor because that just isn't true.
  • swing848 - Monday, December 8, 2014 - link

    At this date, December 2014, with maximum eye candy turned on, there are games that drop a refrence AMD R9 290 below 60 fps on a single monitor at 1920x1080 [using an Intel i5-3570K at 4GHz to 4.2GHz]
  • Sabresiberian - Wednesday, August 22, 2012 - link

    This is not 1998, there are many games built for the PC only, and even previously console-oriented publishers aren't just making ports for the PC, they are developing their games to take advantage of the goodness only PCs can bring to the table. Despite what console fanboys continue to spew, PC gaming is on the rise, and console gaming is on the relative decline.

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