On 13:06 Fri 31 Oct , Stefan Roese wrote:
Hi Wolfgang,
On Friday 31 October 2008, Wolfgang Denk wrote:
It is my understanding that a rework of this code is under way which will avoid the long delay for the standard boot sequence (and only need it for board bringup or intentional recalibration).
Are you talking about storing the optimized autocalibration values in FLASH, as discussed on IRC some time ago? I don't know if somebody is working on
Yes. I see this as a mandatory requirement. The additional delays are not aceptable.
I just want to raise some concerns about this approach on boards with DIMM modules. Here it will be hard to determine if a new DIMM module is installed. Even a module from the same manufacturer and type (size, width etc, all the same) will need a new autocalibration. This is probably hard to detect.
Just my $0.02.
As discuss on IRC with Stefan
we can use the EEPROM present on the DIMM to identify two Modules
as point to this link as example http://www.micron.com/products/spddetail.aspx?part=MT16HTF12864HY-667F1
we have the following interested informations stored
Byte Byte Description Number 64-71 MANUFACTURERS JEDEC ID CODE 73-90 MODULE PART NUMBER 95-98 MODULE SERIAL NUMBER
we can check this 3 fields to be sure if it's a new modules is installed and so re-do the calibration
Why the 3 fields? By experience I've seen 2 Manufacturs use the same Serial Number for 2 differents product and I've also seen a Manufactur using the same Serial Number for 2 differents Part number
Best Regards, J.