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How do I read/modify/flash SPD/XMP profiles on DDR4 EEPROM? - Page 2

post #11 of 49
You're mixing "timings" and "clock ticks".

Don't know if you know this stuff but I'll post it anyway

Memory latency, or timings, like the number 10 in CL 10, are the length of time it takes the memory to complete a step in what it has to do. That "time" is measured in "clock ticks", ie CL 10 takes 10 clock ticks to complete before the memory can move on to it's next operation. The length of one clock tick is the speed at which the memory is running. 1800 MHz memory has a clock tick length of one 1,800,000,000th of a second (1,800,000,000 clock ticks per second), so the CL step takes 10 x 1/1,800,000,000 seconds.

A stick of memory always takes the same amount of time to complete it's CL step (or any other step) no matter what speed it is running. If you run the above memory stick faster, say 2400 MHz, it still takes 10 x 1/1,800,000,000 seconds to complete the CL step, but each clock tick is now 1/2,400,000,000 of a second, so it now would take more clock ticks to complete the CL step. Namely, 24/18 times 10 (for CL step) or 13.3 clock ticks (10 times 24/18 clock ticks). But, alas, that has to be rounded to to CL 14 as memory can't use partial clock ticks..
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post #12 of 49
Thread Starter 
Ok so to be clear, I want to edit the clock ticks of my XMP profile. I don't want to input times in actual fractions of a second in case that's what you thought I was trying to do. Edited the post to make it more clear.
post #13 of 49
This is an interesting idea, I hope you have success.
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post #14 of 49
Thread Starter 
I might not even do it. Can't seem to get any advice other than "don't do it" so it seems I would have to muddle my way through it and probably brick my RAM. New BIOS updates may give access to sub timings clock ticks anyway and improve compatibility with Ryzen's IMC. If it doesn't seem like BIOS updates are going to help I might just try it anyway.

I mean it seems pretty straightforward. You just edit the tables in the editor, fix the checksum, and flash.
Edited by bardacuda - 4/13/17 at 10:46am
post #15 of 49
Quote:
Originally Posted by bardacuda View Post

Ok so to be clear, I want to edit the clock ticks of my XMP profile. I don't want to input times in actual fractions of a second in case that's what you thought I was trying to do. Edited the post to make it more clear.
Read what I posted. You're confusing timing numbers and clock ticks.

For example, what you see in CPU-Z (XMP profile, etc.) are timing numbers. You have to convert those into clock ticks because all motherboard memory control is based on them.
Edited by billbartuska - 4/13/17 at 10:52am
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post #16 of 49
Thread Starter 
If I understand correctly...you are saying I should focusing on modifying the numbers here:



Not necessarily the numbers that show up over here:



Would that be accurate?

I was just going to go with whatever number was looser in the B-die chips *at the same clock speed* and apply that to my E-die. For the timings that are already looser for the E-die, I was going to leave alone.
post #17 of 49
At 1333.33 MHz a CAS setting of 16 takes 12.000 ns to complete.

If you want to change ONLY the timings you can change either the number or the nano seconds. (I would assume that the program will change the other automatically...but then, it's not MY memory sticks that will get borked if it doesn't).

If you want to change speeds and timings, that's whole other ball game.
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post #18 of 49
Thread Starter 
I just want to use the looser "timings" of the B-die on my E-die. For the "timings" that are already looser in my E-die I want to leave them alone. Forgive me if that's not the correct terminology but I think you should be able to understand my meaning.

For clarity, I want to try and overwrite my current 3200MHz XMP profile with a stable 2666MHz profile (and possibly a stable 2933 and then a stable 3200 if I have success). When I open the B-die XMP profile, and change SDRAM Cycle Time to 6 (or 0.750ns) (it is 5 initially because 1600MHz) (yes, the "seconds" field is not editable but updates automatically with the correct value), I see this:



When I open my E-die's XMP profile, and change SDRAM Cycle Time to 6, I see this:



I want to make a new profile like this: (I suspect the system instability at higher memory clocks is because of the sub timings being too tight. This is just an example. I can go looser on the other "timings" if I need to)



I am figuring, in this way, by using the "worst of both worlds", if I flash this and load the XMP profile, what's the worst that can happen? Ok so my new XMP doesn't work. The stock XMP profile doesn't work currently anyway. Can't I just clear my CMOS, boot with an unmodified SPD profile, and flash back to stock? I only want to modify XMP, not SPD.

Isn't there just a guide or a forum thread you could point me to that has this info?
Edited by bardacuda - 4/13/17 at 12:09pm
post #19 of 49
I read this http://www.simmtester.com/page/news/showpubnews.asp?num=184 again, it's useful, dense though.

Thaiphoon had, still has? Write protection testing but it was kinda hazardous. As good a chance to brick ram as full flash. If you haven't, take a quick look at http://www.softnology.biz/tips_wptest.html

The simmtester page may help you determine write protection without blindly testing for it.

always backups. Should make one the second you start thinking of flashing.

Look for spd tables that are closer to your goal, preferably edie. safer bet they'll work
post #20 of 49
Thread Starter 
Thanks! I like it already!
Quote:
Serial Presence Detect (SPD) data is probably the most misunderstood subject in the memory module industry. Most people only know it as the little Eeprom device on the DIMM that often kept the module from working properly in the computer....
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