[Arm-netbook] R-Pi Only Better and More Available?

Gordan Bobic gordan at bobich.net
Thu May 24 14:38:33 BST 2012

On 05/24/2012 02:24 PM, Scott Sullivan wrote:
> On 05/22/2012 05:19 PM, Gordan Bobic wrote:
>> On 05/22/2012 05:57 PM, Scott Sullivan wrote:
> [...]
>>> I really think there is a missed opportunity here without miniPCIe or
>>> SATA. But if this does well we might see more feature rich boards in the
>>> future.
>> It is possible that the Via SoC in question doesn't have SATA and PCI.
>> But the lack of SATA isn't that big a deal.
> That possibility was clear to me, hence my hope for future boards.
> The inclusion of miniPCIe would be the most useful as it means that SATA
> could be added along with media decoder cards for SoCs that doesn't have
> great support.
> http://www.hwtools.net/Adapter/PM362.html
> Video Decoder:
> http://www.mythtv.org/wiki/Broadcom_Crystal_HD
> http://www.alibaba.com/trade/search?SearchText=BCM970015

The other complication is that the fact that SoC has PCIe support, 
doesn't mean that it works properly. The reason why Trimslice has a 
USB->SATA adapter in it for the disk is because they couldn't get the 
PCIe to work with a PCIe SATA controller.

>> Disk I/O is more about IOPS
>> than about MB/s - I get about 2000 IOPS out of a SuperTalent RC8 in my
>> Toshiba AC100 (bottlenecked by USB 2, the RC8 is USB 3 capable) and the
>> performance is pretty amazing:
>> http://www.altechnative.net/2012/02/07/morebetter-internal-storage-on-the-toshiba-ac100-part-2/
>> Sure, a decent SATA SSD will probably beat it, but I would be surprised
>> if you could actually feel the difference on an ARM machine of this
>> performance. My 1.4GHz Tegra2 certaonly ends up CPU rather than disk I/O
>> bound with the RC8.
> I as of yet been unable to source these in Canada.

I ordered mine from an ebay vendor in the far east. Not really a problem 
if you are prepared to wait for a week. But if you are not 
space-constrained, you might as well get a SSD that has both SATA and 
USB ports. There is a flash controler that has both SATA and USB 
interfaces built in - IIRC it was the Jmicron one. It'll be a lot 
cheaper. Not sure how good it is, but it's probably good enough to 
exceed whatever you're going to get out of it over USB2.

> In light of that, a
> SATA interface is preferable to the performance of run of the mill SD
> cards and USB sticks, as you yourself have documented.

Yes, but with a good USB SSD or an external USB-SATA adapter, it'll 
still be more performance than most ARMs can actually usefully handle.

> Additionally SATA
> disk are plentiful and I have a choice of vendors, something that is
> currently not the case for RC8 like USB devices.

True, but if you don't get a jmicron controller based SSD, you can 
always use a USB-SATA adapter. They aren't exactly expensive, and it'll 
still be plenty fast enough.


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