Hi, I did a 771 mod on Asus P5B motherboard. And with xeon in, it doesn’t set memory timings correctly when left on auto. The timings are always set to 5-6-6-15 with tRFC 42, which is a bios default (according to amibcp). It seems to me like some kind of bug. I wouldn’t mind that bug much, if I could set the timings manually. But I can’t, because the maximal value I can set for tRFC is 42 and the memory modules I have requires tRFC 52. So I would like to modify the bios to allow higher tRFC timing setting. I think it should be possible.
This motherboard has a 965P chipset, and according to datasheet, the tRFC timing is set as the lowest 9 bits of CYCTRK ACT register, which should allow setting it as high as 511. I have a Gigabyte motherboard with 965P chipset, which allows tRFC setting up to 511 in bios.
The tFRC setting in the bios is as a multiple choice option (not a number input) and the options are given as “** DRAM Clocks” strings with 5 options, 20 lowest, 42 highest. Those strings can be found in amibcp as strings with tokens 0x041D to 0x0421. I haven’t found what a token means in this context. Is it some kind of pointer used in the bios to reference a string? As I haven’t figure out how to use the token number, I searched for these strings in the bios binary. And I found them in Multi Language module (ID 21 according to mmtool), which seems like a dead end to me as this module is only list of strings. I was hoping that by searching for these strings, I could find a place in the code, when the setting happens. I also tried opening the bios in disassembler (IDA), but I haven’t been able to find anything useful. Probably because I’m not fluent with assembly.
So now I’m lost and don’t know what to try next. Could someone please help me or at least point me at the right direction?
with a similar issue I went for a different workaround, changing the SPD data on the ram modules.
You can use SPDTool for that (be careful and use at you own risk)
http://www.spdtool.com-about.com/
Thank you, but I don’t think it will help in my case. The board completely ignores SPD values and always sets 5-6-6-15 tRFC 42 no matter what ram modules I use. So I guess messing with SPD won’t help me. Or am I missing something?
@gired :
Welcme at Win-RAID Forum!
Since I have no experience with this sort of BIOS modding, I cannot help you.
Did you already contact the ASUS Support?
Regards
Dieter (alias Fernando)
Thank you for welcoming me 
No, I haven’t contacted Asus support, because I don’t think they will help me. I forgot to mention that before the mod, I ran the motherboard with C2D E6400 with no problems. Then after the mod with Xeon E5430, the motherboard runs fine, except for the wrong timings. The P965 chipset doesn’t officially support FSB333 CPUs, even though Asus lists C2Q Q9450 as supported (which is basically the same as E5430). I think that this issue happens only with CPUs with FSB333, but I don’t have any other CPU with FSB333 to test it with. I’ve seen posts complaining about this issue on other forums, but with no solution. It’s also quite old motherboard and of course this mod isn’t officially supported, so I’m pretty sure the Asus support will reply with something like that this CPU isn’t supported. Or do you think that contacting Asus is a viable option?
If not, I wouldn’t have recommended to do it.
To contact the mainboard manufacturer is always worth a try.