RE: Typical bad block counts

RE: Typical bad block counts

[Josh Boyer]

On Wed, 2007-02-21 at 10:44 -0500, Dave Kelly wrote:
> >The datasheet for those chips says up to 20 blocks can be bad.  That
> >includes both Bad blocks at MFG time, and bad blocks that can develop
> >later on.
> 
> No, this is the small block devices for which the max number
> of bad blocks is 160, per the datasheet (NAND01G-A).

Ah, sorry.  Was looking at the large block datasheet.

> My question though is the typical number of initial bad blocks,
> not the max. allowed. No MFG seams to discuss this.

Probably because 1) there isn't a typical number as it varies from
product lot to product lot and 2) nobody has bothered to try and track
it anywhere for the devices they've received.

josh

Re: Typical bad block counts

[Josh Boyer]

On Wed, 2007-02-21 at 10:15 -0500, Dave Kelly wrote:
> On a 1Gbit single level nand (ST-micro), I have 10 chips all with less
> than 6 blocks that are bad originally, a few with none. 
> 
> The chips all bit flip excessively in a few blocks.
> 
> I am suspicious that somebody erased the original marks. The few blocks
> with 0 for the bad block mark all are stuck on 0 for the entire block,
> so could never have been erased anyway.
> 
> What is a reasonable number for bad blocks on this size chip as it 
> arrives from the mfg?

The datasheet for those chips says up to 20 blocks can be bad.  That
includes both Bad blocks at MFG time, and bad blocks that can develop
later on.

josh

Typical bad block counts

[Dave Kelly]

On a 1Gbit single level nand (ST-micro), I have 10 chips all with less
than 6 blocks that are bad originally, a few with none. 

The chips all bit flip excessively in a few blocks.

I am suspicious that somebody erased the original marks. The few blocks
with 0 for the bad block mark all are stuck on 0 for the entire block,
so could never have been erased anyway.

What is a reasonable number for bad blocks on this size chip as it 
arrives from the mfg?

 
Thanks.