Jonathan,
On 9/7/07, Jonathan Pratt Jonathan.Pratt@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.