[Beowulf] getting a phi, dammit.

Vincent Diepeveen diep at xs4all.nl
Wed Mar 6 05:29:11 PST 2013


Speaking of cheap gpgpu - did someone over here benchmark the Geforce  
Titan?
It's not having ECC i assume, yet it is unlimited in double  
precision, running at 1/3 speed
and just $999 and neary 850Mhz.

should be lot of flops and double precision flops.

On Mar 6, 2013, at 10:00 AM, Brice Goglin wrote:

> Le 06/03/2013 07:00, Mark Hahn a écrit :
>> and drop it into most any gen1/2/3 PCIe x16 slot and it'll work  
>> (assuming
>> I provide the right power and cooling, of course.)
>>> The issue here is that because we offer 8GB of memory on the  
>>> cards, some
>>> BIOSes are unable to map all of it through the PCI either due to  
>>> bugs or
>>> failure to support so much memory. This is not the only people  
>>> suffering
>> interesting.  but it seems like there are quite a few cards out there
>> with 4-6GB (admittedly, mostly higher-end workstation/gp-gpu cards.)
>> is this issue a bigger deal for Phi than the Nvidia family?
>> is it more critical for using Phi in offload mode?
>
> Those non-Phi cards have a lot of internal memory but they only  
> export a
> small part of it directly to the host (look at lspci -vvv, you'll see
> only about 200 MB for your big NVIDIA Teslas). This small part can be
> mapped, everything else needs DMA.
>
> Phi lets you map everything (at least in the kernel, not sure if their
> driver lets you map to userspace too) but the BIOS has more work to
> setup such big mappings.
>
> Brice
>
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