Re: NAND technical review

[Jonathan Larmour <jifl at jifvik dot org>]

Jürgen Lambrecht wrote:
> Rutger Hofman wrote:
> > Well, there is no way I can see into the future, but I definitely think
> > that the wire command model for NAND chips is going to stay -- it is in
> > ONFI, after all. Besides, all except the 1 or 2 most pioneering museum
> > NAND chips use it too. There are chips that use a different interface,
> > like SSD or MMC or OneNand, but then these chips come with on-chip bad
> > block management, wear leveling of some kind, and are completely
> > different in the way they must be handled. I'd say E's and R's
> > implementations are concerned only with 'raw' NAND chips.
>
> Correct, only for raw NAND chips to be soldered on a board. The others 
> have an embedded controller and are already packaged.

I don't think E's implementation would have the same problem with OneNAND 
as R's (see below). Yes it has a sort of controller, but it's not as 
advanced as an MMC or SSD one - instead it's there as logic to manage 
exchanges between its SRAM and the NAND array.

> > > One could say that makes it a more realistic emulation. But yes I can
> > > see disadvantages with a somewhat rigid world view. Thinking out loud, I
> > > wonder if Rutger's layer could work with something like Samsung OneNAND.
> >
> > See my comment above. The datasheet on e.g. KFM{2,4}G16Q2A says:
> > "MuxOneNAND™‚ is a monolithic integrated circuit with a NAND Flash array
> > using a NOR Flash interface."
>
> Indeed, a oneNAND is to be threated as a NOR flash, like a pseudoSRAM is 
> a DRAM with SRAM interface.
> And SSD has a hard disk drive interface, just like MMC and SD card; they 
> mostly have a FAT file system on them but also UFS ...

FAOD, I don't believe that's true. You only get a view into a small window 
of the NAND. That small window is memory mapped, but that's all. It's 
certainly not controlled like a NOR flash. It's a NAND, but not one with 
the wire command model that R's implementation assumes.

Jifl
--
--["No sense being pessimistic, it wouldn't work anyway"]-- Opinions==mine