Reviews - Intel Core i7 3960X Extreme Edition CPU

[HEXUS]

There's a new CPU chief in town.

Read more.

[kalniel]

I don't understand something. Page 3 with the chipset diagram you state:

"Chip-to-northbridge bandwidth drops by about 20 per cent as Intel switches from QPI to DMI 2.0"

That seems quite incongruous. 'Northbridge' in X58 just contained the connection to the PCI-E cards. In X79 these are direct to CPU and bandwidth is correspondingly higher.

CPU to PCH (storage etc.) in X58 was via a 2GB/s DMI link. In X79 it's a 20GB/s DMI link.

So 'northbridge' to 'northbridge' comparison X79 is 40GB/s vs X58's 25GB/s (both bi-directional), and a 60% increase. A PCH to PCH comparison X79 is 20GB/s vs X58's 2GB/s, a 1000% increase.

So where does Hexus get its 20% decrease in bandwidth figure from?

Otherwise, great review

[Tarinder]

Nope, you're right, I was inadvertendly comparing QPI to DMI v2.0. That's all well and fine from a specification standpoint but that's not how, as you've correctly pointed out, the chipset's topography works.

[Michael H]

Will the multi-processor Xeon varients feature QPI or DMI for the processor-to-processor links?

You would think there are enough PCIe lanes on each chip to do away with QPI entirely - as you could use half each chips PCIe lanes in dual-processor systems and three quarters in 4-way systems for chip-to-chip communication without sacraficing any lanes for external communication - but I imagine drop-in compatability with s1567 would be possible if it features QPI even if the PCIe lanes would then go to waste.

[kalniel]

Will the multi-processor Xeon varients feature QPI or DMI for the processor-to-processor links?

2x QPI. Servers still have need of PCI-E slots for storage accelerators and GPGPU.

[Michael H]

2x QPI. Servers still have need of PCI-E slots for storage accelerators and GPGPU.

80 PCIe lanes avaliable in a dual-socket system though, 160 in a quad - which would largely be going to waste - QPI does have the advantage of a simpler layout for motherboard.

[cdb000]

I don't think I am going to have one of these, despite the fact that my wife is willing (bless her!) to buy it for me for Christmas -- those two unused cores suggest that an 8 core model will turn up in the next year or so, and that's the CPU I want.

[watercooled]

I don't understand something. Page 3 with the chipset diagram you state:

"Chip-to-northbridge bandwidth drops by about 20 per cent as Intel switches from QPI to DMI 2.0"

That seems quite incongruous. 'Northbridge' in X58 just contained the connection to the PCI-E cards. In X79 these are direct to CPU and bandwidth is correspondingly higher.

CPU to PCH (storage etc.) in X58 was via a 2GB/s DMI link. In X79 it's a 20GB/s DMI link.

So 'northbridge' to 'northbridge' comparison X79 is 40GB/s vs X58's 25GB/s (both bi-directional), and a 60% increase. A PCH to PCH comparison X79 is 20GB/s vs X58's 2GB/s, a 1000% increase.

So where does Hexus get its 20% decrease in bandwidth figure from?

Otherwise, great review

Actually in X79 it's 20Gbits/s, not GBytes.

[kalniel]

Actually in X79 it's 20Gbits/s, not GBytes.

Well spotted. Sneaky Intel changing units.

[watercooled]

Something else I've just noticed on that diagram - look at the RAM bandwidth for the X58 system. It should be GB/s not Gb/s.

[watercooled]

Anyone else had this problem?
http://www.phoronix.com/scan.php?pag...tem&px=MTAyNzE

Sounds like Vcore might be set too low?

[kalniel]

Something else I've just noticed on that diagram - look at the RAM bandwidth for the X58 system. It should be GB/s not Gb/s.

Heh yes! Even Intel are confusing the two. Serve them right for trying to market-speak specs.