On 14/11/13 17:50, Jensen, Jens (STFC,RAL,SC) wrote:
> During my phone call with Chris W yesterday, he mentioned that the ARM
> PIs have the wrong kind of ARM in them.
Details are:
http://www.raspbian.org/RaspbianFAQ#What_is_Raspbian.3F says;
"Raspbian is an unofficial port of Debian wheezy armhf with compilation
settings adjusted to produce code that uses "hardware floating point",
the "hard float" ABI and will run on the Raspberry Pi.
The port is necessary because the official Debian wheezy armhf release
is compatible only with versions of the ARM architecture later than the
one used on the Raspberry Pi (ARMv7-A CPUs and higher, vs the Raspberry
Pi's ARMv6 CPU).
The Debian squeeze image issued by the Raspberry Pi foundation was based
on debian armel which uses software floating point and the "soft float"
ABI. The foundation used the existing Debian port for less capable ARM
devices. Therefore, it did not use of the Pi's processor's floating
point hardware - reducing the Pi's performance during floating point
intensive applications - or the advanced instructions of the ARMv6 CPU. "
> He also mentioned the eagerly
> anticipated 64 bit one. I like ARM but don't exactly follow them
> day-to-day, but praps there is more to come in the future on that front,
> too.
They are available in quantity in IPhone 5s and the new iPad, but not in
quantity on any other device.
One of the Debian porters (who works at ARM) wasn't able to obtain
hardware...
>
> Or we could of course build a quantum computer - which requires,
> theoretically, no power, as long as the transforms remain unitary (no
> measurement). Also generates no heat until you do your measurement,
> because no information is lost. (Disclaimer: IANAP!)
Chris
>
> Cheers
> -j
>
> On 11/11/2013 13:32, Matt Doidge wrote:
>> On 11/11/2013 12:49 PM, Stephen Jones wrote:
>>> On 11/07/2013 08:45 AM, Jensen, Jens (STFC,RAL,SC) wrote:
>>>> They get fewer events per minute per core than on Xeons, but more
>>>> events per minute per Watt.
>>>
>>> I wonder how XEONs and Pi's stack up. It would be good to compare these.
>>> Have you any typical events per minute per watt values to plug in?
>>>
>>> If we convert the ARM's events per minute per watt to events per
>>> KWH, we
>>> can use the cost of 1 KWH (£0.10) to get "events per £" or the energy
>>> cost
>>> of one event etc. It would be good to know if there is a huge
>>> difference.
>>
>> *Spoiler alert for those who haven't read the paper[1] yet - all I'm
>> doing is regurgitating[2] the numbers here.*
>>
>> The article has figures of 1.14 events/minute/watt for arm CPUs, and
>> 0.21 events/minute/watt for hexacore xeons. The power consumption is
>> estimated from the TDP of the CPUs, so isn't fully indicative of total
>> power draw of the servers doing their thing (particularly spinning all
>> those disks), but it's a good place to start.
>>
>> Converting to KWH to gives 68,400 arm events per KWH, and 12,600 Xeon
>> events/KWH.
>>
>> Of course, the ARM events/minute/core were roughly a third that of the
>> Xeons, and time is money, but this argument could be counter-countered
>> by just how many ARM chips manufacturers could shoehorn into
>> specialist boxes.
>>
>> Definitely worth keeping an eye on.
>>
>> Cheers,
>> Matt
>>
>> [1]http://xxx.soton.ac.uk/abs/1311.0269
>> [2]I also apologise for using the word regurgitate. It's not a
>> pleasant word.
>>
>>>
>>> Cheers,
>>>
>>> Steve
>>>
>>>
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>>>
>>> Events per minute per watt is a measure of how much work a watt can do
>>> in a minute (or how much work a minute can do with a watt!)
>>>
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>
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