[Beowulf] El Reg: AMD reveals potent parallel processing breakthrough

[Vincent Diepeveen]

Also utter useless it is, as the GPU has what is it 200GB/s bandwidth,
going back to 6GB/s cache coherent gpu/cpu (just taking a number i've  
seen more there get claimed
that the bandwidth was in OpenCL) you lose roughly factor 30+ so  
using such features is total nuts.

On May 1, 2013, at 11:41 PM, Mark Hahn wrote:

>> On 05/01/2013 08:51 AM, Christopher Samuel wrote:
>>> This sounds interesting..
>>>
>>> http://www.theregister.co.uk/2013/05/01/amd_huma/
>
> unfortunately, nothing much new there.  we knew from other leaks that
> there would be systems with both normal ddr and gddr mapped into the
> same coherent physical space.  that's really the point of the whole
> HSA thing, and goes along with the impending placement of ram chips
> onto the APU package by both AMD and Intel.
>
> this is a very good thing for HPC.  it's obviously not hard to build
> even conventional SIMD CPU architectures that have serious bandwidth
> issues with conventional cache-mitigated dram.  even without resorting
> to GPU-like wider arrays of ALUs.  I don't see that it'll complicate
> much - just another flag to mmap (like MAP_HUGETLB).
>>
>> "In today's CPU-GPU computing schemes, when a CPU senses that a  
>> process
>> upon which it is working might benefit from a GPU's muscle, it has to
> ...
>
>> That last time I checked, CPUs don't sense anything - the  
>> programmer has
>> has to write the program to  use the GPUs muscle.
>
> I'm shocked that anyone would accuse theregister
> of whimsey or anthropomorphization!
>
> though in a narrow sense, "sense" here could mean "application called
> ACML's FFT with appropriate size/params, so use GPU rather than CPU".
>
> anyway, here's my understanding of the state of things:
>
> - there will be a Haswell chip with in-package ram of some sort.
> it's extremely unclear what kind of ram, though - some people claim
> it's a custom 128M edram (not sure why 'e', since it's not embedded)
> there are also claims this acts as last-level cache.
>
> - AMD is making APU chips that will talk both ddr and gddr,
> the latter presumably on-chip.  they'll be shipping significant
> volumes by way of xbox-next and ps4 consoles...
>
> - Nvidia has a plan for in-package dram as well, but it's years away.
>
> - HMC consortium (incl Micron, Samsung, IBM, but not Intel) has a
> standard that seems well-suited for integration via 2.5d interposer.
>
> from an HPC perspective, faster memory is unambiguously good, even if
> it's fixed in size, unupgradable, asymmetric.  turning the GPU into  
> more
> of a first-class on-chip functional unit will provide a much more  
> managable
> programming model.
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