RE: dynamic memory detection

["Zimman, Chris" <czimman at bloomberg dot com>]

Alfred,

In general, you can find what you're looking for via the SPD (Serial
Presence Detect) EEPROM on the DIMMs.  You read them via I2C, and they
contain the row and column info as well as timing for the DIMM.  You can
use this information to calculate the size of the DIMMs.  AFAIK, this
has been on all DIMM modules since SDRAM became standard.

The IXP425 has some restrictions on the DDR configurations it can
support, so this probably isn't that big of an issue for people
designing systems around it.

Here's a link for some further info on SPD:

http://www.simmtester.com/page/news/showpubnews.asp?num=101

Hopefully whoever did the board design wired the I2C bus through to the
DIMMs.

--Chris

-----Original Message-----
From: ecos-devel-owner@sources.redhat.com
[mailto:ecos-devel-owner@sources.redhat.com] On Behalf Of alfred hitch
Sent: Wednesday, May 11, 2005 3:38 AM
To: Robin Randhawa
Cc: ecos-devel@ecos.sourceware.org
Subject: Re: dynamic memory detection

Hi Robin,

thanks for your reply,

but could u please give more details on ur SDRAM sizing algo ?
how were u doing that ?

then I will see if I can do the same on IXDP or not .. 
My fear is that I cannot as I was discussing with someone who has
worked extensively on x86 plattforms.
In there on northbridge there is a device generally which can be read
to find the size etc of dram ,

as of now I dont see any such stuff on ixp data sheet.

May be this is the reason that redboot etc dont have this as it might
not be a portable feature, but come to think of it, on boards where
one can, it should be implemented ?

can u tell how u did the sdram sizing thing ? I can infact choose
u-boot also as my bootloader that isnt the issue presently.

Alfred