Hey people
 
Just wanted to share some good vibes here!
 
Background story 
As some of you who now me a bit from past (I abandoned this forums for over a year) I was messing with GTLVREF manual settings in past to no avail. I was trying to find a sweet spot based on trial & error method which I utterly failed on (too many variables for a quad core chip) .. and wasted over a month on doing so ... well it wasn't just me, there were much more people involved, but only a few succeeded in achieveing better stability at lower FSB termination voltage (VTT) with adjusted GTLVREF, given the overclock is perfectly stable to begin with - goal is only to lower the VTT ... and possibly lower the VCC (core voltage) a little at same time too.
 
Recently I found an old thread (linked not so long ago by VistaHead) where tt0ne posted some interesting information:
http://forums.evga.com/tm.aspx?m=835180
 
here are the very informational links (general info) provided by tt0ne in above thread (no need to read all):
http://www.anandtech.com/show/2482
http://www.anandtech.com/show/2500
http://www.anandtech.com/show/2404
http://www.thetechreposit...wthread.php?t=87 

So, here is the deal. It worked for me (worked differently for tt0ne though hehe).
based on above knowledgeable articles, especially the one on ASUS Striker II Extreme board and their GTLVREF adjustment example, here below I was able to lower VTT from 1.25V to 1.15V (100% stable) at 450MHz FSB:
http://www.anandtech.com/show/2500/18
 
Point is that assuming the 790 board per Intel reference specs automatically adjusts (at least data lanes, as addressing lanes seem to be untouched on 790) to 67% of current VTT (FSB termination voltage) and a fact (some statistical info quoted by Anandtech) that 45nm quads like running at 67-70%, while 45nm dual cores like stability at 63-64% then depending on which chip type you have, you will be going either to manually reduce the GTLVREF or increase it, based on whatever the board/BIOS shows currently at given FSB speed for data lane(s).
 
Believe it or not, but I succeeded in actual calculation of all 4 GTLVREF values for my 790 Ultra board and Q9450 chip giving me perfect stability at  450MHz FSB - being 1800MHz for linked/synced DDR3 RAM (3.6GHz on my chip with 8x multi) at only 1.15V VTT (FSB termination voltage)... now consider this, with GTLVREF in automatic mode the lowest VTT making this overclock stable was ... 1.25-1.30V
 
Calculator 
I created a downloadable Google Documents spreadsheet. Just input desired VTT (FSB termination voltage) at given automatic GTLVREF values (790 shows those only for data lanes, it doesn't adjust the addressing lanes) and the script will calculate the rest for you (guessing address lane value)
https://spreadsheets.goog...S&authkey=CK7OwKUF
Use option File -> Download as -> Excel to get a local copy of this scripted file. Input your own numbers in yellow fields only. The results are displayed in Cyan fields. Dual Core results are untested (and likely wrong as only 3% reduction was used, while 4% might be needed for better results).
 
How this works 
The idea is to assume that automatic 790 chipset GTLVREF adjustments (at least for data lanes) put the numbers at exactly 67%, so it needs to be further positively adjusted for a quad core chip (increase actual GTL voltage by 3%) or negatively adjusted (reduce actual GTL voltage by 3%).
Addressing lanes are a guesswork, I only assumed that initially they should show same values as data lanes and then I was adjusting them (either up for a quad, or down for a dual) by HALF of adjustment given to data lanes.
 
I'm pretty confident, based on my own experience that data lanes adjustments are close to stable, however addressing lanes are more guesswork, so that's what I did and it worked for me at least.
 
Assuming that 790 Ultra board does SOME automatic adjustment and actually shows automatically adjusted GTLVREF values for data lanes (first two GTLVREF lanes with 45nm quad, only the first GTLVREF lane with 45nm dual)
 
Again, it may or may not work for you, especially if you have a different variant of board or chip than I do. The results may get you closer to success, so you will know soon upon testing with Prime Blend (30 mins stable is good enough), if system freezes using desired VTT and adjusted GTLVREF then something is wrong.
Check for how long each time it takes for the test to freeze the system, this way you will know if you are adjusting them in right direction.
Very bad values will cause a system freeze in seconds, while better fitted values will be able ti run Blen test for minutes before it freezes (usually in less than 10 minutes).
 
Eventually once you pass 30 mins in Prime Blend x64 26.6 (both 720K FFTs and 8k smallFFTs tests) then run 10 rounds of Intel Burn Test 2.51 in Max stress mode and make sure it really is stable. It was for me
 
I have notes from every step of process, I even tried (again) some manual trial error once I got closer, but my problem was settings all lanes (both data and both addressing) to same value. After I adjusted addressing lanes to half of relative adjustment (calculated offset) set on data lanes, it just worked and passed all tests like a charm.
 
A word of note on GTLVREF addressing lanes (last one for dual and 2 last ones for quad, as shown in 790 BIOS).
Since 790 chipset board does NOT adjust or show addressing lane GTLVREF in automatic mode, then it can be assumed that initially those lanes *should* be set to same value as data lanes.
It's not a problem at lower clocks because the window of opportunity is wide enough to gain stability (at higher VTT), but surely it limits quad overclocking at higher FSB. Also dual cores may be actually much easier to overclock on 790 board, because it seems the board does a better job in automatic GTLVREF adjustments for those chips. DOn't have a dual core so can't check if calculations are anywhere correct for those.
 
This thinking (setting all lanes to same values as tt0ne did -35 on all lanes with his setup) got me MUCH closer to gaining some stability at 450MHz FSB (1800MHz on linked/synced DDR3 RAM) and using only 1.15V FSB (VTT), but Intel Burn Test BSOD'd (stop 124) after 4 rounds and Prime Blend was freezing after like 6 minutes.
 
Please do not flame this thread (that's what happened to old now archived thread on same topic) as it WON'T work for many of you, sometimes your setup will be totally different, some other times your specific hardware (chip + board combo) will yield different results.
 
I am curious to see if those scripted calculation work for anybody else besides me
 
My own examples
1.
401-450MHz FSB range
 
a) Former stable 1800MHz/3.6GHz clock (450MHz) voltages at GTLVREF on auto (showing -50,-50,0,0 in BIOS):
vcore 1.437V (as set in BIOS, actual 1.36V) - 1 notch lower value was sometimes failing the test
vtt/fsb 1.25V-1.30V (1.25V was causing this overclock to freeze sometimes when gaming)
spp 1.55V (likely overshot by 1 notch, but 1.45V was giving me errors under IBT and SLI was flakey)
mcp 1.50V
memory 1.7V (2x2GB p1p2 enabled, 8-8-8-22-2T)
Stability tested in SLI mode enabled under Intel Burn Test 2.51, 10 rounds in max stress mode.
 
b) Current same stable voltages for same speed as above, just GTLVREF adjusted to -15,-15,-30,-30:
vcore 1.431V (as set in BIOS, actual 1.36V)
vtt/fsb 1.15V <==-- THIS IS FULLY STABLE NOW
spp 1.50V (1.45V is fully stable under IBT and Prime Blend, but causes problems with SLI and watching movies)
mcp 1.50V
memory 1.7V (2x2GB p1p2 enabled, 8-8-8-22-2T)
Stability tested in SLI mode enabled under Intel Burn Test 2.51, 10 rounds in max stress mode. also 30 mins of running Prime Blend x64 26.6 (720K and 8K passed).
 
2.
451-500MHz (or more?) FSB range
 
a) Former stable 1866MHz/3.73GHz clock (466MHz) voltages at GTLVREF on auto (showing -80,-100,0,0 in BIOS):
vcore 1.491V (as set in BIOS)
vtt/fsb 1.30V
spp 1.55V
mcp 1.50V
memory 1.8V (2x2GB p1p2 enabled, 8-8-8-22-2T)
Stability tested in SLI mode enabled under Intel Burn Test 2.3, 10 rounds in max stress mode and over 8hrs of Prime Blend.
 
b) Current same stable voltages for same speed as above, just GTLVREF adjusted to -40,-60,-60,-80:
vcore 1.491V
vtt/fsb 1.20V <==-- THIS IS STABLE NOW
spp 1.55V 
mcp 1.50V
memory 1.65V (2x4GB p1p2 enabled, 9-11-9-27-2T)
Stability tested with 32 mins of running Prime Blend x64 26.6 (720K and 8K passed).
 
 
Stress Testers used:
 
a) Intel Burn Test 2.51:
http://majorgeeks.com/IntelBurnTest_d5987.html
 
b) Prime95 x64 26.6:
ftp://mersenne.org/gimps/p64v266.zip
 

Thanks VistaHead!

I hope this info helps someone. Not sure if it really does though as adjustments calculated above are generic so there might be some trial and error involved working around the numbers to reach the sweet spot.

This has been posted a few times, been a while though and the member that did it has not been here for a few years.. Good stuff...
 
AB Was Here...

hehe, yeah it's a kind of boomerang topic
 
Thanks!
 
posted it mostly, because wanted to share.
the calculated numbers worked for me so well that I couldn't believe in what just happened
 

Afterburner

This has been posted a few times, been a while though and the member that did it has not been here for a few years.. Good stuff...

AB Was Here...

 
Thank you
 
I hope it's at least a bit useful.
For FSB values over 450MHz, where the GTLVREF data lanes show automatically -80,-100,0,0 (with quad) I think the calculation is correct or very close to correct on data lanes only. I am totally unsure about addressing lanes.
I am pretty sure that half of calculated offset is what addressing lanes should receive, but am unsure of their initial values, I don't believe they are at 0 at all.
 
I haven't found yet the fully stable GTLVREF at 1.20V target VTT for over 1800MHz (e.g. 1866MHz or 1920MHz or 2000MHz), but it's much better than on automatic settings anyways. there is still many combinations around calculated numbers.
 

sirdx

Great Thread, feniks.
Thanks for the GTLVREF calculator.
It works geat.

long time no see
 
thanks bro!
 

Stray_Bullet

Nice & Hello! =)

Ok.....let me run this by you for verification and or correction.
 
I am currently running rock-solid stable at 1800MHz Linked and Synced w/ 8GB's of RAM (4x2) with the below BIOS settings:
 
**Memory Timing Setting**
Memory Timing Setting: [Expert]
tCL (CAS Latency): 8
tRCD: 8
tRP: 8
tRAS: 18
Command Per Clock: [2T]
 
** Advanced Memory Settings **
tRRD: [7]
tRC: [46]
tWR: [12]
tWTR:[19]
tFAW:[35]
tREF:[7.8uS]
tRFC:[100]
 
[**System Voltages**
CPU Core: [1.325v](VDrooped to 1.288v @ idle in Windows)
CPU FSB: [1.3v]
Memory: [1.90v]
nForce SPP: [1.45v]
nForce MCP: [1.55v]
 
GTLVREF Lane 0: [-50mv] 
GTLVREF Lane 1: [-50mv]
GTLVREF Lane 2: [+00mv] 
GTLVREF Lane 3: [+00mv]
 
If I change my GTL's to as close to these that can set: -15.5 -15.5 -32.5 -32.5........I may be able to get my Vcore down to 1.15v???

Yes...as I stated, " w/ 8GB's of RAM (4x2) ".......and there is no VTT setting in my BIOS vP09.

feniks

VTT=CPU FSB
VCC=VCORE=CPU CORE

Just goes to show that old dogs CAN learn new tricks!! Thankx, man. I wonder why they are not labled like that in the BIOS then?

OK...so with this new knowledge.....my choices on the GTL settings are this, since there are no .5's available:
 
(1) -15 -15 -30 -30 (closest to the chart) or
 
(2) -20 -20 -35 -35
 
And if I set in #1...then I should be able to lower my current FSB of 1.3v down to 1.15v.....correct???

Thank you for the great explaination. I appreciate it very much.

OK, this is starting to amaze me
 
just had a chance (lower ambient, heat wave is gone) to run prime blend for higher clocks with higher vcore...
 
last time i was testing 1864MHz (466 even FSB per my calculator) and I couldn't find stability, was only able to find longest non-freezing under Prime Blend set of GTLVREF numbers.
again they were VERY close to calculated numbers.
 
calculated (quad on 790, over 450MHz FSB clock with initial -80,-100,0,0 GTLVREF):
-44,-64,-62,-82
 
the ones surviving longest before freeze were -40,-60,-60,-80 ... today I adjusted clock to 1866MHz (FSB not so even per my calculator, it says 466.5MHz) and bam! it worked again :)
 
so mind the FSB clock you are running as whatever you run *should* fit the base bootstrap numbers for the CPU and memory (1864 is not good, while 1866 is).
 
Prime Blend ran successfully for 32 mins completing the Large FFT 720K and then Small FFT 8K on all cores with VTT at 1.20V running 1866MHz (3.73GHz on my Q9450), formerly with automatic GTLVREF only achievable with VTT at 1.30-1.35V
 
... however I don't even want to talk about vcore I had to use under Intel Burn Test to be stable ... better do not ask me for that ... can only say that hitting 80C under full CPU stress can't be good ... not for long at least ...

there is only a hardware way of lowering vcore since the chip's core power demand depends only on 3 things: clock, board's design (and its BIOS) and chip itself (values are unique to every chip even among same model and batch).
 
there is a pencil mod which worked for 780 boards, however it does not work on 790. it reduces vdroop by means of applying pencil graphite to one of board's resistors. for 790 it was a failure, no positive results from anybody what so ever, so it's considered a dead end.
 
other option is to use FTW board which allows for vdroop control (Ultra boards do not have it).
 
what chip needs is what it must get in order to run stable, period.
 
temps can be controlled by means of upgraded cooling, e.g. tons of high efficiency (high CFM rates) fans or water cooling, but it does not affect vcore needs, only allows to control resultant temps better, nothing more.
 

JeffreyHam

While I do find what you are doing very interesting.....I believe that finding ways to lower the VCC at higher speeds would be the most beneficial as, that is what produces the most chip heat.

Oh...I agree with you completely. For me personally....I just don't see any tangible advantage for me to spend so much time working on lowering my VTT by adjusting the GTL's when I am easily able to run stable at pretty much any speed I desire while using the Auto GTLVREF settings.
 
This is kind of old but, does show some good examples. All the GTL's were set on Auto and then manually set using the same values after passing stability tests.
 
http://forums.evga.com/tm.aspx?m=598716

Thankx, man. 1936MHz was the highest I could go and keep my VCC under 1.3625v. I'm sure that you already know that is the max safe voltage as stated by Intel. It was also the highest I could go with my air cooler and keep it under 80C under IBT Max Stress load. I cannot afford to just go out and replace my CPU if I damage it so, that's where I stopped.
 
For everyday use, 1800MHz is plenty fast and cool so, that is where I run.

Well...like I told you on that other thread awhile back.......it took me 4 months to save up the $325 to buy my chip. My common sense tells me to not do anything stupid that would destroy it in a matter of moments....whhat would be the benefit of that?
 
I have taken plenty of risks in my life which have produced good results but, knowingly doing something ignorant and expecting to get good results out of it is not wise....JMHO.