B3 with different RAM chips

Tiago Marques tiagomnm at gmail.com
Mon Apr 19 20:51:10 EDT 2010

Hi John,

I'm trying out some new USB Flash drives from Sony that are quite
fast(random write speed) compared to the SD cards shipping in the XO 1.5 and
I'd just like to ask you something about the test script running on the
Sandisk Extreme III:

[edit] Sandisk Extreme III

There are four XOs at 1CC running the tests on a SanDisk Extreme III 4-GB SD
> card. Build 8.2-760 was freshly installed on the laptops.

The current test rates are roughly 3.8 sec/test step 4.1, and 4.1 sec/test
> step 4.2. This translates roughly into a 17 MByte/s read rate, and a 5.7
> MByte/s write rate.

Laptop Serial # Test Total Written

 SAN1 SHF725004D1 Wear & Error 30,550

 SAN2 SHF7250048F Wear & Error 28,335

 SAN3 SHF80600A54 Wear & Error 28,730

 SAN4 CSN74902B22 Wear & Error 29,250

Am I getting this right? They endured 30TiB of writes and still did ok?
Did they start marking bad blocks as unusable, thus shrinking the drive, or
did they remained with the same 4GB without failing?
What are the results you obtained with the SD cards for XO 1.5 and which
cards did you settled with?

I haven't checked the brand of the sample in my B2 but it's been running
rock solid as far as I can tell, the only problem is it being so slow with
random writes because otherwise the 1.5 is quite a capable machine.

Best regards,

On Sun, Nov 29, 2009 at 4:47 AM, John Watlington <wad at laptop.org> wrote:

> Be aware that the test.sh script tends to be destructive to the device.
> If a device is close to failing (which is when you start seeing
> a larger number of errors), they will push it over the edge quickly.
> Some less reliable cards fail after as little as 900 GB written.
> Cheers,
> wad
> On Nov 28, 2009, at 1:31 AM, Richard A. Smith wrote:
>>  Can you provide me with the software or scripts you use to do your
>>> internal SD card testing? I would love to put this card and the other
>>> more reliable SanDisk one I have to find out if it is a problem with
>>> the 1.5 card reader or the SD cards.
>> It's the same scripts used for NAND testing.
>> http://wiki.laptop.org/go/NAND_Testing
>> Git repo:
>> http://dev.laptop.org/git/users/wad/NANDtest/
>> --
>> Richard A. Smith  <richard at laptop.org>
>> One Laptop per Child
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