[MLC NAND]: data pattern sensivity

[Jeff Lauruhn (jlauruhn)]

I read back through the posts and I think we are talking about 2 separate things, random read time and randomization. 

Rand Read (tR) assumes you are doing a single read of a page (worst case), but most data is stored in blocks sequentially, so data output can be improve significantly by read by taking advantage of commands like READ PAGE CACHE SEQUENTIAL which copies the next sequential page from the NAND Flash array to the data register.

Randomization is a relatively new feature, I'm no expert, but it's in general we know there are some distributions that are worse than others, and by randomizing the data we can avoid worst case and improve endurance.


Jeff Lauruhn
NAND Application Engineer
Embedded Business Unit
Micron Technology, Inc


-----Original Message-----
From: Boris Brezillon [mailto:boris.brezillon at free-electrons.com] 
Sent: Tuesday, April 07, 2015 8:09 AM
To: Andrea Scian
Cc: Jeff Lauruhn (jlauruhn); mtd_mailinglist
Subject: Re: [MLC NAND]: data pattern sensivity

On Tue, 07 Apr 2015 15:21:25 +0200
Andrea Scian <rnd4 at dave-tech.it> wrote:

> Thanks for linking this again.
> I think that Jeff can help us in understanding this further.
> The documents is pretty old (2009) and is about TLC only.
> Does it mean that MLC are less (or not at all) affected by this issue?

Some MLC chips require a randomization step: take a look at this datasheet [1], page 21:
"Users are required to employ randomizer function in the NAND controller to meet target endurance of the device."

[1]http://www.100y.com.tw/pdf_file/37-SAMSUNG-K9GBG08U0A-SCB0.pdf


--
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com