B3 with different RAM chips

John Watlington wad at laptop.org
Tue Apr 20 15:54:28 EDT 2010

On Apr 19, 2010, at 8:51 PM, Tiago Marques wrote:

> 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?

No, that was 30K cycles (times 20MB/cycle) or just 600 GB.

> 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?

An SD card sets aside between 5 and 10% of the raw storage for use in fixing bad blocks.
Thus, you will see no change in the size of the card over time, until it runs out of spare blocks
and fails completely.

We didn't settle on "one card", and even if I tell you the manufacturer and size it won't help
as most have various OEM models for a given size.

> 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.

Are you running into the SD card errors on an XO-1 ?


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