[U-Boot-Users] SDRAM on ixp425

[Leon Woestenberg]

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.