Quote Originally Posted by massman View Post
A few days ago, I ran some tests on the way the ram timings effect the SPI run (I tested the basic timings, not subtimings). My conclusion: no effect on how 32m is calculated.
Thanks mate.

No effect at all? Are you talking about how the graph pattern looks or the times in seconds? Your subtimings were changing too so I can never be sure what is causing the lowering of times because those were the exact subtimings which were giving me lower/higher times.
Beware, SPi is strongly divider/strap based in my experience and can easily make one lead to making false conclusions (it did with me anyway). 32M I can have one setting and run CAS4 4-4-4-4 and get time x and then change it to CAS5 5-5-5-8 and still get x+1 second depending on which strap I'm on. At a quicker strap this won't be the case. However, at faster straps the PL doesn't allow to be changed below 7 and the board is running quicker (more efficient) than at higher speeds/lower PL/higher tRFC (same other settings). You'd have to boot at every strap and divider to see this, and it takes about a week... I know, I tried it.

I'm not using the DS4 now to compare.

The obvious point of all this is to compare with OPB's gain and his timings were quite high so we have to work out what and why are the possibilities of SPi behavior in a given situation which could allow 1second 1M drop at lower frequencies/higher timings than a run with higher frequencies/lower timings. That's looking very tricky and I'm stumped.

Quote Originally Posted by Zeus View Post
Now running DDR800 with for example cas4, we have 4x2.5ns=10 ns latency, running cas5 at that same speeds gives 12.5ns latency and so on, needless to say, the more latency the slower the run will be.

Now it becomes obvious that running 5-5-5 at 600MHz is almost as fast as 500MHz 4-4-4 and 500 5-5-5 is as fast as 400 4-4-4.
Thanks Zeus.
Tha's exactly what I look for to see if my times are faster than they should be or slower. On the DS4 that pattern was not being observed in 1M/2M unfortunately. 620 4-4-4-4 was just as fast as 450 4-4-4-4. 32M however does show the difference quite clearly.