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Motherboard for 3 dual-width PCIe 3.0 GPUs, and single Core i7 3930K

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June 25, 2012 3:35:59 PM

I have a challenge.

Is there a motherboard that can support:
1 CPU: LGA2011 Socket, Intel Core i7 3930K
3 GPUs: dual width, PCIe 3.0 x16 (x16 mode).

I have found several motherboards that can support 3 dual width PCIe 3.0 x16 GPUs and the Core i7 3930K CPU, but in most cases, one or more GPUs will have a PCIe transfer speed of only x8 mode rather than x16, because the PCIe x16 slots are such that the operate at x16 mode speed when the neighboring slot is unoccupied, and at x8 mode speed when the neighboring slot is occupied.

Any suggestions ?
a b V Motherboard
June 26, 2012 1:25:29 AM

1. LGA 2011 (x79) uses PCI-E 2.0
2. thats because x79 has 40 PCI-E lanes 16 * 3 = 48, so the best config would be 16 * 2 + 8 * 1 = 40

( * means multiply just to clarify)
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June 26, 2012 2:32:57 PM

Thanks for your response:

"LGA 2011 (x79) uses PCI-E 2.0"

Then why do all the motherboards have mainly PCIe 3.0 slots ?

"thats because x79 has 40 PCI-E lanes 16 * 3 = 48, so the best config would be 16 * 2 + 8 * 1 = 40"

That depends on the motherboard doesn't it ?
This one http://www.asus.com/Motherboards/Intel_Socket_2011/Ramp...
can have:

4 x PCIe 3.0/2.0 x16 ( x16/x8/x8/x8, red)
1 x PCIe 3.0/2.0 x16 (x8 mode, gray)
1 x PCIe 2.0 x1

which looks like it has 49 lanes in total right ?

In theory maybe there could be a configuration where I could have 3 GPUs in there, all at x16 ?
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a c 717 V Motherboard
June 26, 2012 3:12:18 PM

If you can afford the ASUS Rampage IV Extreme then buy it and stop looking -- you found the best.

Technically, the SB-E can support PCIe 3.0 and on AMD GPU's they all run PCIe 3.0 but on nVidia you need to run this mod - http://nvidia.custhelp.com/app/answers/detail/a_id/3135... ; nVidia took the approach of validation and decided to Disable PCIe 3.0 support thought the Registry.

The SB-E only has 32 PCIe lanes to the GPUs, 40 PCIe lanes in total, and even though I've seen "( x16/x8/x8/x8) in reality it's -> ( x8/x8/x8/x8), and the other 8 PCIe lanes are 2.0 to the remainder of the chipset and all other PCIe bandwidth requirements.
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June 26, 2012 3:28:38 PM

Thank you VERY MUCH .. you might be saving my day here .. Jaquith,
Most of the MSI mobo's have max memory supported of 128GB (for example: http://eu.msi.com/product/mb/X79A-GD45--8D-.html#/?div=... ) , while all the Asus ones have max of 64GB ... which makes me want to stay away from Asus.

Also, when you say SB- only has "32 lanes to the GPUs"
Are you saying that can not have (x16, x16, x8) with SB-E ???
If there's 40 lanes in total, how can there only be 32 to the GPUs ? Like, how does it know where I'm putting the GPUs ?

Also if it only as 40 lanes in total, then all these X79 mobo's built for the core i7 are overspecked, because they usually have way more PCIe 3.0 lanes.


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a c 717 V Motherboard
June 26, 2012 3:52:12 PM

ASUS will also handle 16GB/sticks when non-ECC (consumer) RAM is available; currently it's RDIMM (Server/Workstation RAM for Xeon/Opteron). The specs are like the X58 that originally was 6x4GB (24GB) but any i7-9XX I've seen can run 6x8GB (48GB).

Most 3-WAY's are running (x16, x8, x8) but it depends on the MOBO and what PCIe slots and in particular how they're shared. Further, the ONLY instance where I've seen any advantage to PCIe 3.0 over PCIe 2.0 is with 4-WAY GTX 680 with >HD resolutions; nice Thread - http://www.evga.com/forums/tm.aspx?m=1537816

It's not 'IF' it's the Intel spec (search 40) - http://en.wikipedia.org/wiki/LGA_2011

--

/edit - You are confusing Slots (PCIe x16) or (PCIe x8) with Bandwidth (x16/x16 or x16/x8/x8 or x8/x8/x8/x8).
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June 26, 2012 4:11:24 PM

Wow Jacquith!
THat's really helpful !

So based on that wiki page, there's 40 lanes for the "primary PCI" and 8 lanes for the "secondary PCI" ... since the GTX GPUs require 16 lanes .... only "primary PCI" lanes can be used for GPUs ??? Did I understand you correct ?

In that case, is it possible for me to find a configuration where can have 3 GPUs at speeds: (x16 x16 x8) using the 40 lanes of the "primary PCI", and then this RAID controller in the "secondary PCI" ??

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June 26, 2012 4:17:38 PM

Also, Jacquith, further to my reply above,
I'm having trouble following "ASUS will also handle 16GB/sticks when non-ECC (consumer) RAM is available; currently it's RDIMM (Server/Workstation RAM for Xeon/Opteron)"

If you don't mind, could you please rephrase that for me ?
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a c 717 V Motherboard
June 26, 2012 4:25:05 PM

Duh nope, SB-E (LGA 2011) is 40 PCIe lanes 8 of which are PCIe 2.0 and for the chipset, etc and the 32 PCIe PCIe 3.0 (with mod) - period.

GPU Bandwidth (x16/x16 or x16/x8/x8 or x8/x8/x8/x8)

The LGA 1155 is 24 PCIe lanes 8 of which are PCIe 2.0 and for the chipset, and the 16 IB = PCIe PCIe 3.0 or 16 SB = PCIe 2.0- period.

GPU Bandwidth (x16/x0 or x8/x8) ; unless the Z77 uses a third-party chipset e.g. PLX
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June 26, 2012 4:30:22 PM

The wiki page you sent said there's 40 Main PCI lanes, and 8 Secondary PCI lanes .. so it's not possible for me to use 40 lanes (PCIe 2.0) or 32 lanes (PCIe 3.0) for GPUs, in the Main PCI , and use the secondary PCI for my RAID controller ?

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a c 717 V Motherboard
June 26, 2012 4:41:59 PM

You are reading only what you want to see and we're going in circles. 40 Total split into 32 & 8 as I posted above more than once.

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a b V Motherboard
June 26, 2012 4:52:36 PM

Jaquith is absolutely right, there are 40 PCIe lanes in the spec for the X79 chipset, so it doesn't matter what board you're looking at. None of them will have 48 lanes split among 3 slots.
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June 26, 2012 5:02:01 PM

So the wiki page he posted is very misleading ... it certainly makes it look like it's 40+8.

So I can put 3 GPUs: 16 + 8 + 8 = 32 , and the RAIN controller ?
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a c 717 V Motherboard
June 26, 2012 6:01:57 PM

WIKI has had info wrong and/or unclear before, in this instance it's unclear.

Assuming you meant the 'Intel RAID controller' that's part of the DMI 2.0, in this case Intel X79 controller, which has 20 Gbit/s with a x4 link bandwidth {20 Gbit/s = 2,560 MB/s} ; DMI 2.0 - http://en.wikipedia.org/wiki/Direct_Media_Interface Other non-native chipsets share PCIe 2.0 x8 lanes {8*500MB/s = 4000MB/s}.

2 SATA3 = 600MB/s (ea) * 2 = 1200MB/s
4 SATA2 = 300MB/s (ea) * 4 = 1200MB/s
14 USB 2.0 = 60MB/s (ea) * 14 = 840MB/s

Total = 3,240MB/s max theoretical bandwidth.
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a c 717 V Motherboard
June 26, 2012 10:48:11 PM

PCIe 2.0 x4 port (500*4=2000MB/s max)

Q - What's the intended use?

I'm not a fanboy of Highpoint Rocket and since this is external I assume it's for some External Data drives?
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June 26, 2012 11:04:47 PM

jaquith said:
PCIe 2.0 x4 port (500*4=2000MB/s max)

Q - What's the intended use?

I'm not a fanboy of Highpoint Rocket and since this is external I assume it's for some External Data drives?


jaquith said:
PCIe 2.0 x4 port (500*4=2000MB/s max)

Q - What's the intended use?

I'm not a fanboy of Highpoint Rocket and since this is external I assume it's for some External Data drives?


Thanks again for replying Jaquith !

What don't you like about Highpoint Rocket ? It's just a RAID controller isn't it ?

Okay so the use is this... I only have 64GB of RAM and I'm dealing with 1.2 TB matrices ... when the RAM runs out the data gets moved to SWAP .... I've tried this in the past with an HDD but it was extremely slow just do deal with 1.2GB let alone 1.2 TB !!

I'm hoping that trying this SSDs would work better ... I have three 512GB SSDs that I hope to combine in a RAID 0 to get my 1.2TB matrix stored temporarily for some computations.

What's your opinion on Dereck47's reply to my post on this thread: http://www.tomshardware.co.uk/forum/286127-14-match-spe... ?
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a c 717 V Motherboard
June 27, 2012 12:23:25 AM

644L - http://www.highpoint-tech.com/USA_new/series_rr640L.htm

Reason, Highpoint's are cheap and not nearly as reliable as LSI or Adaptec.

Thread - all Intel X79 SATA ports 'can' be linked together as a 6 drive array, but any parity RAID e.g. 5 would be much slower. 'Real' speed depends on file size (structure), and if everything is in 4KB then SATA2 vs SATA3 per drive means nothing - neither is saturated.

IF you want more speed the choices are: RAM Drive or RAID 0 with a 'Good' Controller and one with both 1GB Cache + Battery back-up and e.g. LSI with it's (FastPath SW Key).

Example look at my 4KB:
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July 4, 2012 12:42:54 AM

Best answer selected by healthyman.
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a c 329 V Motherboard
July 4, 2012 12:33:51 PM

This topic has been closed by Nikorr
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