[Beowulf] ARM cpu's and development boards and research

[Bill Broadley]

On 11/27/2012 07:46 AM, Vincent Diepeveen wrote:
> i dug around in price of ARMs and development boards.
> 
> If you just buy a handful most interesting offer seems to be
> 
> http://www.hardkernel.com/renewal_2011/products/prdt_info.php? 
> g_code=G133999328931
> 
> it's $129 and has a quad core ARM cortex A9 at 1.4Ghz and a mali gpu  
> on it.
> 
> So from raw cpu cores this is by far best offer on the market,  
> nothing even gets close to it,

Maybe if you want the maximum cores per $ regardless of performance.

Atom boards are likely to give you:
* substantially better CPU performance
* 10x the network bandwidth
* 4x the memory size

Like say the $70 board with a D2500 (1.86GHz dual core) or the $80 D2700
(2.1 GHz dual core/4 thread).

> The number of quadcore offers is pretty limited in ARM world - it's  
> nearly all dual cores there.

Umm, you seem to be ignoring quite a few quad core arm chips.  Like say
the nexu s4, nexus 7, nexus 10, and many others.  Both the tegra quad
core and the Snapdragon quad core seem rather common.

> This CPU should be eating at 1.0Ghz exactly 3 watt under full load  
> and a tad more at 1.4Ghz,
> though the "1.4Ghz" clock i couldn't confirm in an easy manner. Could  
> be the quadcore version is 1.0
> Ghz after all.

Sounds like hand waving to me, have you actually measured this?  Were
all cores and network in use?  Was it diskless?  ssd?  sata?

> The cortex A15 that goes in production in 2013 maybe, that one is 64  

Er, the cortex-a15 is 32 bit, it has a PAE like extension to allow bank
swapping.  You probably mean the cortex a57 which is 64 bit (and not
shipping)

The cortex a15 however shipping in tablets (the nexus 10), laptops (the
chrome book), and motherboards (the Arndale).

The A15 benchmarks look pretty good compared to the A9, TI has an OMAP
5, Samsung has the Exynos 5250.

My interest in Arm has been the flip side of balancing flops to network
bandwidth.  A standard dual socket (AMD or Intel) can trivially saturate
GigE.  One option for improving the flops/network balance is to add
network bandwidth with Infiniband.  Another is a slower, cheaper, cooler
CPU and GigE.

> A big hurdle always is the many dual core ARMS out there which do not  
> have fast RAM yet which only have

I believe the cortex a15 substantially improves memory bandwidth.