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post #431 of 439
Do PCI-E lanes off the CPU have any advantage over lanes off the chipset when it comes to installing things other than GPUs, ie. less latency?
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post #432 of 439
As far as motherboards go, I think the current ones w/BIOS updates should do just fine. I have been using the Rampage IV Extreme w/BIOS 4004 (the first BIOS to supposedly support IVY-E for RIVE) at some pretty fast memory settings without any issues whatsoever.

I added a 3970X not too long ago for work and play, with an upgrade to a 4960X in mind...turns out that the 3970X is a good performer and its IMC had been running 32 GB of G.Skill 2400 MHz at ultra tight timings...until I plugged in 4x4 of G.Skill 2666 MHz destined for an Ivy 3770 just to see - -the Sandy-E runs 2666 MHz just fine also...'upgrading' to an Ivy-E won't happen soon unless I can find a binned 4960X that actually outperforms the current Sandy-E.
3970X G.Skill 2666 Spoiler! (Click to show)
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Edited by Joa3d43 - 8/23/13 at 3:02am
post #433 of 439
Quote:
Originally Posted by Oubadah View Post

Do PCI-E lanes off the CPU have any advantage over lanes off the chipset when it comes to installing things other than GPUs, ie. less latency?

More total bandwidth, while it'd be fine for most rigs, if you were wanting to run a RAID card and already had a lot of SSDs, HDDs and USB3.0 devices (Or Networking, especially 10Gbit/s Ethernet) on your SB at once then you'd probably hit the 4GB/s limit between the PCH and CPU although it was much more of an issue with the 1155 and before chipsets iirc.
post #434 of 439
Quote:
Originally Posted by Oubadah View Post

Do PCI-E lanes off the CPU have any advantage over lanes off the chipset when it comes to installing things other than GPUs, ie. less latency?

The sole purpose of the PCI-E bus is to connect a component with the CPU, hence obviously, intercommunication is much less important than CPU connectivity.

Now, after that obvious advantage of the CPU as the main beneficiary, there are some limited advantages of inter-connectivity. e.g. 2 GPUs being more 'comfy' than on x8x8.
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post #435 of 439
Quote:
Originally Posted by Oubadah View Post

Do PCI-E lanes off the CPU have any advantage over lanes off the chipset when it comes to installing things other than GPUs, ie. less latency?

There is definitely less latency, as the PCIe data does not have to hop over the chipset.

In addition, Sandy Bridge E/EP and Ivy Bridge E/EP use DMI to connect to chipset, which has limited bandwidth in itself - you could stress it with too many fast SSDs as well.

So, yes, using CPU's built-in PCIe controller has both bandwidth and latency benefits.
post #436 of 439
Quote:
Originally Posted by Oubadah View Post

Do PCI-E lanes off the CPU have any advantage over lanes off the chipset when it comes to installing things other than GPUs, ie. less latency?

Yeah, PCI express on the PLX chip has more latency than CPU lanes - There is a good writeup at anandtech about this, although I don't have it bookmarked. They had a quad SLI round up like a year ago or something, and they had a detailed technical article about PLX + latency.. That is why LGA 2011 is preferable over any mainstream platform (z87/z77/etc) for quad SLI.....

Besides which, X79 motherboards are cheaper than mainstream Z87/Z77 PLX motherboards for the most part anyway, rendering the point moot. Why bother with quad SLI Z87 when the PLX motherboard is 450$ ? Sounds stupid to me.. Just get x79 and use the difference towards a LGA 2011 CPU.
Edited by xoleras - 8/23/13 at 3:28pm
post #437 of 439
Quote:
Originally Posted by xoleras View Post

Yeah, PCI express on the PLX chip has more latency than CPU lanes - There is a good writeup at anandtech about this, although I don't have it bookmarked. They had a quad SLI round up like a year ago or something, and they had a detailed technical article about PLX + latency.. That is why LGA 2011 is preferable over any mainstream platform (z87/z77/etc) for quad SLI.....

Besides which, X79 motherboards are cheaper than mainstream Z87/Z77 PLX motherboards for the most part anyway, rendering the point moot. Why bother with quad SLI Z87 when the PLX motherboard is 450$ ? Sounds stupid to me.. Just get x79 and use the difference towards a LGA 2011 CPU.

I wasn't talking about PLX chips or GPUs, I meant CPU lanes vs z87/x79 lanes with things like sound cards, NICs, PCI-ESSDs, etc.

I don't know why those mainstream boards with PLX chips even exist.
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post #438 of 439
Even in case of non-GPU workloads there are high-bandwidth ones, like modern SSDs.

As far as I remember, current DMI bandwidth is 20 Gbit/s - this is 2.5 GB/s.

Some SKUs of Patsburg (C60x) have additional 4 PCIe lanes dedicated for SAS uplink. Where present, this uplink does help with the off-CPU bandwidth a bit.

But where not available, it is quite easy to saturate DMI 2.0 bandwidth with modern SSDs.

According to the public datasheet: http://www.intel.com/content/dam/www/public/us/en/documents/datasheets/c600-series-chipset-datasheet.pdf

X79 does not seem to have the additional PCIe x4 uplink between the PCH and CPU. I am not 100% sure if this is up to date or if anything changed, but if it is indeed correct - then you can definitely saturate X79 chipset when using its PCIe connections for fast storage and such.
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