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Old 2016-02-12, 20:38   #1
Mark Rose
 
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Default AMD Zen speculations

The latest slide to leak is that Zen may have up to 8 channels of DDR4.

http://www.extremetech.com/extreme/2...ddr4-interface
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Old 2016-02-12, 21:51   #2
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My 12 core AMD chip has 2 NUMA nodes and each node has their own memory channels.
(Each NUMA node owns some of the RAM and one node accessing the other nodes memory is something like 50% slower.)

One way AMD could have 32-core and 8 DDR4 channels, is to have 4 NUMA nodes of 8 cores each. Each node has 2 DDR4 memory channels. Of course, this is just speculation.

The question for prime95 is how many FPU the 32-cores will have?
The 12-core AMD has 6 FPU.
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Old 2016-02-12, 22:36   #3
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Quote:
Originally Posted by Mark Rose View Post
The latest slide to leak is that Zen may have up to 8 channels of DDR4.
But will it not suck horribly at AVX/AVX2? Inquiring minds want to know.
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Old 2016-02-12, 22:53   #4
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Quote:
Originally Posted by bgbeuning View Post
My 12 core AMD chip has 2 NUMA nodes and each node has their own memory channels.
(Each NUMA node owns some of the RAM and one node accessing the other nodes memory is something like 50% slower.)

One way AMD could have 32-core and 8 DDR4 channels, is to have 4 NUMA nodes of 8 cores each. Each node has 2 DDR4 memory channels. Of course, this is just speculation.

The question for prime95 is how many FPU the 32-cores will have?
The 12-core AMD has 6 FPU.
With zen there will be an equal number of fpus and cores.
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Old 2016-02-14, 17:26   #5
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Quote:
Originally Posted by Mark Rose View Post
The latest slide to leak is that Zen may have up to 8 channels of DDR4.

http://www.extremetech.com/extreme/2...ddr4-interface
It would be a beautiful option
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Old 2016-03-14, 20:15   #6
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The latest news is that AMD engineers have achieved better than the 40% IPC improvement talked about earlier, and that it's somewhere between Broadwell and Skylake.

The 8 core (16 thread) chip should have a 95 watt TDP and be out in October.

http://wccftech.com/amd-zen-cpu-8-co...ching-october/

I think I may pre-order one when possible.
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Old 2016-03-14, 21:13   #7
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Quote:
Originally Posted by Mark Rose View Post
The latest news is that AMD engineers have achieved better than the 40% IPC improvement talked about earlier, and that it's somewhere between Broadwell and Skylake.

The 8 core (16 thread) chip should have a 95 watt TDP and be out in October.

http://wccftech.com/amd-zen-cpu-8-co...ching-october/

I think I may pre-order one when possible.
If I understand correctly, the Summit Ridge FX chips will only have dual channel RAM. Would the 8-channel versions be Opterons?
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Old 2016-03-14, 21:27   #8
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I think I may pre-order one when possible.
I would wait. IMO, Bulldozer's AVX implementation was so stupendously bad that they probably need to triple IPC (or more) before they become competitive again.

Last fiddled with by Prime95 on 2016-03-14 at 21:28
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Old 2016-03-14, 21:47   #9
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Quote:
Originally Posted by Prime95 View Post
I would wait. IMO, Bulldozer's AVX implementation was so stupendously bad that they probably need to triple IPC (or more) before they become competitive again.
I hope we find out more about the AVX implementation before the release date.

The chip's lead architect, Jim Keller, also lead the K8 architecture and co-authored X86-64. So I am hopeful it is well done. Time will tell though!
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Old 2016-03-14, 22:12   #10
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Quote:
Originally Posted by kladner View Post
If I understand correctly, the Summit Ridge FX chips will only have dual channel RAM. Would the 8-channel versions be Opterons?
I have no idea if they'll call them Opterons. That brand name is kind of tarnished.

I hope they call everything Zen. AMD already has excitement around that name.

The 8 channel, 32 core chips come from the CERN slides. Given that Zen is structured around modules of 4 cores, it would make sense if they have one memory channel per module.

Of course, with less than perfect yields, I bet they'll sell chips with cores and the consummate amount of L3 cache disabled, which will hopefully improve the memory bandwidth situation. I'm curious what the officially supported DDR4 frequency will be.
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Old 2016-03-14, 23:05   #11
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I hope I'm wrong with what I'm about to write...

From the earlier link, there is suggestion that a Zen core has two 128-bit FP units that can join together to do 256-bit. Haswell has two 256-bit units per core. Assuming they're equally efficient per clock, does that mean you'd need two Zen cores to match one Haswell? So Zen possibly having 8 cores might only be around parity with an existing Intel quad.

Dual channel ram for 8 cores sounds weak to me. Put it this way, say if Zen floating point is as good as Haswell per core, its memory bandwidth requirements are going to be serious. This might be mitigated if all cores work on the same task. Has there been any speculation on possible cache sizes? A generous dose of last level cache could help a lot.

So, I really hope either the info is wrong, or my interpretation is wrong, as I'd love to see more viable prime-finding CPUs than the current game of which Intel do I try next.
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