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yurtesen
Miniboss

PCIe x16 Gen 3.0 chipsets?

Does anybody know if there will be, or is  PCIe x16 Gen 3.0 chipsets from AMD? or chipsets from another company which can work with bulldozers?

I find it strange that HD 7000 series support it but one has to buy an Intel system to use it.....Wouldnt you agree?

27 Replies
yurtesen
Miniboss

Re: PCIe x16 Gen 3.0 chipsets?

Does this mean AMD is soon going out of chipset manufacturing? I guess this could give a hit to the AMD CPU sales too if there would be no possibility to get an AMD CPU which can be used with a motherboard which supports PCIe Gen 3.0.. ?

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Skysnake
Adept II

Re: PCIe x16 Gen 3.0 chipsets?

Hi, i´am no AMD stuff, but when you know how the chipsets are connected with the AMD CPU and so on, you know, that it make more or less no sense to use PCI-E 3.0 interface, because you don´t have enough bandwidth.

The interconnect between CPU and chipset, which provides the PCI-E lanes, is limited to 20.5 GB/s per direction. So you can utilize only one 16x PCI-E 3.0 link and one 4x PCI-E 3.0 link. So only single Card machines would have a benefit.

But you shouldn´t forgett, that you have also all your SATA Ports, onboard sound, USB, PCI, LAN and so on the same! HT link, where the PCI-E data goes through.

The problem is, AMD still just use HT3.0 which is limited to 20.5 GB/s per direction with a 32Bit link. As far i know you have only one of this 32 Bit links at a desktop machine, and also all chipsets have only one 32 Bit link.

There is the HT3.1 version out since 2008, but this also just provides 25.6GB/s per direction for a 32 Bit link. So there is no big improvement. As far i know the FX CPUs should be HT3.1 ready, but i am not sure.

So if you really want PCI-E 3.0 you should have 2 HT link, what is no problem. But then you have the same number of HT links, like for Dual-Sockel Systems. And you need a more complex Moterboard, and a new chipset with 2 HT links, or 2 chipsets. And of course the chipsets have to be PCI-E 3.0 capable.

I don´t think, AMD will do this, but i hope. But there is also a problem. The chipset is powerhungry, so you increase you powerconsumption again with this, and still yet AMD burns to much power at the Desktop.

When you have a look at the APUs, it looks much better. AMD have there also the PCI-E lanes in the CPU (or will have) like Intel. So there shouldn´t be any big problems to bring PCI-E 3.0 to the APUs. But there you haven´t the big CPU power...

No lucky situation for AMD.

yurtesen
Miniboss

Re: PCIe x16 Gen 3.0 chipsets?

If there is not enough bandwidth, AMD should fix the problem. It is hardly a solution to not provide PCIe 3.x because of such reason.

In either case, it is enough if they can support one 16x PCIe 3.0 for a starting point. It is better to have this than not have it at all. Now you dont have any choice but go with Intel if you will use even one 16x PCIe 3.0

Also, PCIe 2.x have a lot of overhead which does not exist on PCIe 3.x as well as probably there wont be multiple lengthy transfers to many cards at the same time so a PCIe switch could be used and still could provide significant bandwidth increase and decrease in latencies.

I am not sure who is directing these decisions at AMD. But it looks like it  is poor decision to not to support PCIe 3.x.

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Skysnake
Adept II

Re: PCIe x16 Gen 3.0 chipsets?

It is possible, that they will support PCI-E 3.0 with the next chipset, but then only 1 Slot, and you also have than only this 4-9 GB/s for all the other devices. For a really heavy use machine this is not aceptable.

Just the sockel 1155 systems (IB) will give you the same or more Bandwidth.

And forgett the switches. You don´t need them for the AMD-systems. They have them integrated in there chipsets (more or less). You can split the bandwith dynamicaly between the targets.

For more HT-links you have to change the sockel, and that make no sence. AMD is far behind Intel atm in the Desktop market, when you look only on CPU-Power. With GPUs it is the opposit. Intel is far behind AMD (yet).

We really have to look, what will come.

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yurtesen
Miniboss

Re: PCIe x16 Gen 3.0 chipsets?

Skysnake wrote:

It is possible, that they will support PCI-E 3.0 with the next chipset, but then only 1 Slot, and you also have than only this 4-9 GB/s for all the other devices. For a really heavy use machine this is not aceptable.

Well, some bandwidth is shared, but then the so called heavy load might be difficult to generate under normal circumstances. Intel is not much further away either, the only way they can provide PCIe is with the lanes on the CPU, no?

Anyway, it is a must for AMD to provide some sort of PCIe 3.0 support, otherwise....

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Skysnake
Adept II

Re: PCIe x16 Gen 3.0 chipsets?

Yes and No. They have Lanes directly from the CPU but also some Lanes from the Chipset.

There DMI is nothing else than a propriat PCI-E interface with some specials.

So they have no problem for there 16 PCI-E 3.0 lanes on the 1155 Systems, like it would be more or less with a AMD System. As far i know DMI2 are just 4 PCI-E 2.0 lanes. So you have there again 2 GB/s.

So yeah, if AMD would bring a PCI-E 3.0 chipset, you would have the same performance like with the IvyBridge platform from Intel, or better, a littlebit more, because of the limited DMI from Intel for SATA Ports and so on.

But there is also Sockel 2011 from Intel with its 40 3.0 Lanes, and this is definitly another lvl.

So AMD can only compare with Intels midrange platform. Bot as bad as i thought before i go into the details. Under this view a PCI-E 3.0 chipset make sense for AMD3+(what ever).

But for the long terme AMD have to do something, but more in CPU-Performance, because they have always the option to more HT links for more PCI-E lanes. I hope we will se a 56 PCI-E 3.0 lane chip from AMD in the near future.

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yurtesen
Miniboss

Re: PCIe x16 Gen 3.0 chipsets?

Skysnake wrote:

But there is also Sockel 2011 from Intel with its 40 3.0 Lanes, and this is definitly another lvl.

So AMD can only compare with Intels midrange platform. Bot as bad as i thought before i go into the details. Under this view a PCI-E 3.0 chipset make sense for AMD3+(what ever).

Yes, but socket 2011 is for performance and high-end server platforms. AMD has C32 and G34, for example C32 works with 2x HT links

http://en.wikipedia.org/wiki/Socket_C32

Intel has 2x QPI on 2011.. 

http://en.wikipedia.org/wiki/List_of_device_bit_rates

AMD processors have twice the bandwidth of what Intel can provide, no?

Also, which cpu+chipset from Intel is providing 40 PCIe 3.0 lanes? Isn't it 40 PCIe 2.0 lanes? They have only 16x PCIe 3.0 lanes at most...

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Skysnake
Adept II

Re: PCIe x16 Gen 3.0 chipsets?

Yes and No. Sockel 2011 is also a Desktop system. So you can get from 1 sockel up to 4 sockel in one System with the sockel 2011.

The Sockel 2011 QPI runs with 8.0 GT/s not with the 5.86 or 6.4 GT/s like the old one. So you should have =>32 GB/s with the Sockel 2011 QPI. Yes this is less than with HT, but for one Sockel systems this is not important. It is only important, if you need more bandwidth between the CPUs than QPI can give you. But i have to say, that i wonder, that HT is so much faster than QPI. Perhaps one of the reasons, why the people like the Opterons for HPC.

All Sockel 2011 CPUs have the ability for 40 PCI-E lanes, but the Desktop CPUs have only 2.0 certification, but intel say, that it is possible, that 3.0 speed is abailible.

The same CPU as Xeon (the new stepping for core ix) have 3.0 certification.

16x PCI-E 3.0 will have the in the next month comming Ivy Bridge CPUs for Sockel 1155.

EDIT:

With 2 Sockel 2011 Xeons you can have up to 80 PCI-E 3.0 lanes

EDIT2:

Ok, some more informations about QPI for the new Xeons.

Have a look onto this: http://novatte.com/blog/2012/03/5-reasons-to-consider-switching-to-intel-e5-2600-series-cpus-startin...

It look like there are 2 QPI Ports for interconnect between 2 CPUs possible. So you will have up to 64 GB/s of bandwidth between this two CPU, what is more than with HT as far i know.

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yurtesen
Miniboss

Re: PCIe x16 Gen 3.0 chipsets?

If you go multi-socket, bulldozer is surrounded by hypertransport links and these are used in opterons...

2 QPI (6.40GT/s) links is same speed as single HT 3.1 link....?

http://en.wikipedia.org/wiki/Opteron#Opteron_.2832_nm_SOI.29

In any case, PCIe 3.0 is a must that AMD must provide. They have to solve whatever issues they are having... That is my point

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