Hi Felix,

I will soon have to port U-Boot to a custom board based on AMCC 460EX CPU. This board should be very close to Canyonlands evaluation board, but board designers decided to use DDR1 instead of DDR2 present on Canyonlands.

Looking at U-Boot 1.3.3 code, I can see that DDR1 support for 460EX is available in cpu/ppc4xx/cp44x_spd_ddr2.c. My question is - was DDR1 support ever tested on 460EX. Another question is - are there DDR1 DIMMs that can be used on Canyonlands ?

DDR1/DDR2 support is available on many processors, but the hardware layout is memory specific.

I don't have a Canyonlands board, but if it was designed for DDR2, then it will be setup with a 1.8V DDR supply and 0.9V VTT supply, so you will *not* be able to use DDR1 DIMMs on that specific hardware implementation.

A DDR1 board would be designed to use a 2.5V DDR supply, and 1.25V VTT termination voltage, along with lots of termination resistors.

So if you have DDR1 on your board, you will need to work out the DDR1 settings. If the layout of your board is identical to the Canyonlands board, then likely you can copy all that boards general settings, and then apply the DDR1 specific settings. If you board layout is different, then you'll need to start from scratch - which isn't that hard.

One thing that can really help in determining the DDR1 settings required, is a board-level post-layout simulation. Your hardware engineer should have performed a simulation during board layout to make sure the clock delays and voltage ringing on the transmission lines was all in spec. So there should be some useful information there for you.

For example, I am using a Freescale MPC8349EA PowerQUICC II Pro. It has clock and data-strobe adjustment registers, which we use to align the clock and data correctly. We had to make sure there would be a valid setting that would work for us, based on the relative clock-and-data timing shown in the post-layout simulations. As far as customizing the DDR setup relative to a Freescale evaluation board, I pretty much copied the basic settings, and then adjusted the drive-strength and clock-alignment for my specific layout.

You'll have to do something similar.

Cheers, Dave