Transfer rates with NAND

Transfer rates with NAND

[Indrek Kruusa]

Hi,

I am wondering which NAND transfer rates are seen in embedded Linux 
projects. What to expect from the whole hardware/software subsystem?
I have one Geode LX design with CS5536 companion chip which by using 
built-in 8-bit Flash controller on PCI bus gives me slightly over 2MB/s. 
It's almost the same with Linux MTD driver and with a self-made basic 
driver. Is the speed here the matter of flash controller only? Which is 
the fastest flash controller out there? :)

thanks in advance,
Indrek

Re: Transfer rates with NAND

[Enrico Migliore]

Indrek Kruusa wrote:
> Hi,
>
> I am wondering which NAND transfer rates are seen in embedded Linux 
> projects. What to expect from the whole hardware/software subsystem?
> I have one Geode LX design with CS5536 companion chip which by using 
> built-in 8-bit Flash controller on PCI bus gives me slightly over 2MB/s. 
> It's almost the same with Linux MTD driver and with a self-made basic 
> driver. Is the speed here the matter of flash controller only? Which is 
> the fastest flash controller out there? :)
>
> thanks in advance,
> Indrek
>
>   
Hi Indrek,
 
 the data transfer from the NAND to the CPU and viceversa depends on:

 1. NAND bus maximum speed
 2. CPU's bus controller speed (*) and its configuration
 3. Read or Write operarations

The overhead added by the MTD layer or any other well written driver is 
irrelevant.

(*) I mean the bus that access the NAND which might not be the same bus 
that access the RAM

Enrico

Re: Transfer rates with NAND

[David Woodhouse]

On Thu, 2006-12-21 at 13:44 +0200, Indrek Kruusa wrote:
> I am wondering which NAND transfer rates are seen in embedded Linux 
> projects. What to expect from the whole hardware/software subsystem?
> I have one Geode LX design with CS5536 companion chip which by using 
> built-in 8-bit Flash controller on PCI bus gives me slightly over 2MB/s. 
> It's almost the same with Linux MTD driver and with a self-made basic 
> driver. Is the speed here the matter of flash controller only? Which is 
> the fastest flash controller out there? :)

The CS5536 NAND flash controller is fairly crap in terms of performance
-- you don't get burst read/write transactions over PCI with it, so it
goes very slowly as it has to do the whole PCI setup thing for every 4
bytes.

You'll get a maximum of something like 3 MiB/s from it IIRC. From a
better controller and a decent chip you might get close to ten times
that; at least in theory.

-- 
dwmw2