[U-Boot-Users] SDRAM on ixp425

[Jonathan Pratt]

Hi Leon.

The processors parts are B1 stepping (ABB - running at 266MHz). Both
SDRAM parts are -7. 

Interestingly, if I use the uboot version for the 128Mbit parts on the
boards populated with the 64Mbit parts (ie CFG_SDR_CONFIG set to 0x18)
then uboot will boot (looking for all the world as though it is
configured correctly). However, with an incorrect SDRAM configuration,
there are holes in the RAM memory and memory checks fail.

Therefore the SDRAM timing seems to be OK. The configuration for 64MBit
parts is what seems to be killing the system.


Jonathan Pratt
ELPRO Technologies Pty Ltd

-----Original Message-----
From: Leon Woestenberg [mailto:leon.woestenberg at gmail.com] 
Sent: Friday, 7 September 2007 9:29 PM
To: Jonathan Pratt
Cc: u-boot-users at lists.sourceforge.net
Subject: Re: [U-Boot-Users] SDRAM on ixp425

Jonathan,

On 9/7/07, Jonathan Pratt <Jonathan.Pratt at elprotech.com> wrote:
> Hi all.
>
> We have an ixp425 product with a footprint for 2 SDRAM components. 
> When we use 2 x IS42S16800 (8M x 16 x 4 banks) for a total of 32MByte 
> everything works fine. But replacing these components with 2 x 
> IS42S16400 (4M x 16 x 4 banks) for a total of 16MByte the board won't 
> boot.
>
> ...
> The first version works fine (using 8Mx16x4 parts). The second version

> fails to boot with the appropriate components (-7 {143MHz} speed
grade).
>
Both are -7 parts? And, please mention the product code on the IXP. Is
it a B-0 or B-1 stepping? There were some issues with some speed parts,
the main reason for the B-1 stepping.

Here are some notes I can access now:

    *  PRIXP420BD - Intel IXP420 B-0 stepping, 533 MHz, lead-free
    * PRIXP420ABD - Intel IXP420 B-1 stepping, 533 MHz, lead-free
          o For the B-1 stepping the SDRAMs must have a minimum refresh
cycle time (tRC or tRFC) of 67.5 ns or less. The Intel software must be
modified as per page 47 of Software Specification Update.
          o The two 32-bit -7 parts currently selected (Micron and
ISSI) do not fulfill this requirement. Either a faster part, or two
16-bit parts in parallel are required.
                + No faster parts are available, or hardly available.
Two 16-bit parts in parallel are required.


I think the 16-bit parts have -6 speed grade, which is why they work.
I can look into our design notes next week.



Regards,

Leon.