Quote:
Originally Posted by stealth17
I agree.. Im sure there will be plenty of us including me doing the mod once its complete..
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Quote:
Originally Posted by stealth17
I agree.. Im sure there will be plenty of us including me doing the mod once its complete..
--- Cat --- A replacement regulator is indeed best way... but cost is higher ;)
--- Persivore --- Pin 4 of the RT9173A IS connected to the midpoint of the divider... so in effect you have pin 2&3 shorted together on your schematic if you leave Pin 4 of the RT9173A connected to the MB. ;) You would need to either lift pin 4 on the RT9173A (and then ground it to disable the RT9173A's output), or simply lift pin 5 which is it's output so it's out of the circuit. The resistors of the VMem divider used to generate Vref are 10 ohms. 2nd comment on your circuit is that FET will be seeing about 6W average and 12W peak using +5V as the source. 3rd comment is that a Vtt regulator must be able to not only source current, but also sink current to function properly ;)
--- uwackme --- Richtek is gonna wonder why the interest from so many places ;) BTW... I was thinking something more like the first attachment below for mounting method... remember the tab is connected to Vmem.
-----
The 2nd attachment is a block diagram of one of the 3 alternate methods I previously mentioned as a possibility (other 2 already discussed)... since no real power in the circuit, no HS required...could be made on a small perf board. Basis for it is to adjust the reference input to the RT9173A so it's output tracks properly under load, increasing it's reference when it starts to droop. Caveat - the RT9173A can't be going into current limiting for it to work (which it may be doing).
Peace :toast:
I like the idea EMC, good solution to mounting. Only hard solder is the Vmem to #2 regulator...dont want to fry it, but the conductor needs to be 18GA or better.
Idea is to solder #2's pins directly to #1's pins... no wires ;) (the tab is VCtrl input - it isn't connected to the tab for current capability - DFI just used Vmem to supply Vctrl)
With Vctrl being Vmem, maybe we are seeing a amplification/feedback of slight noise/load-droop in Vmem back around into Vtt? Wonder if pulling Vctrl in the air and attaching to 3.3V or 5V rail would magically make the droop vanish?
I would use 3.3V but I have a feeling it would help.Quote:
Originally Posted by uwackme
hmm maybe i do :) On the other hand i can see many enthusiasts having especially the dfi nf4 :)Quote:
Originally Posted by alpha0ne
No, doesn't vanish, but helps lower RdsOn and thus minor improvement in droop... Oskar already tested that in this post. Haven't heard back if he's gone to the 4V+ level yet.... if it wasn't such a pita to do, would have already tried 5V myself ;)Quote:
Originally Posted by uwackme
Peace :toast:
i know this is about the mod, but could anyone give information how the OCZ booster would affect the VTT issue ? I still did not hear conclusive things regarding the booster and the VTT stability.
If it works it would be a alternative for people who dont want to take risks soldering/modding on the board and it would be relatively cheap to do.
Does the booster even interface with Vtt? Isnt Vtt only supplied to the terminating resistors, and not to the DIMM socket at all?
Wonder if shorting Vref to Vtt and using a booster would then let the Booster's regulator Vref output help stabilize Vtt?
Vref has a seperate supply correct? There is no droop on it.
Looks like the ultimate solution is for DFI to come out with a new rev of MB and we go buy that.
That might be the ultimate fix, but for everyone else that got the board that isn't fixed (if it even is or will be) then finding a mod that solves the problem is a must...and I'm sure with the people here we can do itQuote:
Originally Posted by uwackme
Short Vref to Vtt and you'll have an oscillator and maybe toast :p:Quote:
Originally Posted by uwackme
Ugh, didnt realize Vref was just off a resistor voltage divider. Yuck.
Sucks that Vctrl is on the tab, tie it to 3.3Vrail, setup a seperate POT based voltage divider to dial in 1/2 Vdimm value'd Vtt and see if droop vanishes.
What kind of bypass caps have they implemented on the Vtt resistors? Starting to think they didnt use ANY, where there should be 560pf and .1uf ceramic cap for every 4-8 resistors in the terminator network.
Did you see the "rev2" board layout.... looks like the same Vdimm/Vtt circuit.
Sigh.
At this point it begs the question.... any other NF4 boards having such issues? Time to consider Asus or Abit and just voltmod them.
hmmm....any news ? My finger is itching and wants to mod...this issue is too serious to just ignore.....if i knew the OCZ booster helps i would get one....but still no real information if it would affect VTT..
What about a voltage divider between VIN and REFEN?
-CaT
--- Flexy ---
Waiting on some parts... something about a slow boat... may be a bit :/
seems the vdimm mod made my vdimm unstable. jumps a lot now. anyone else have this?
As far as I know, the DDR Booster does not directly fix VTT tracking issues.Quote:
hmmm....any news ? My finger is itching and wants to mod...this issue is too serious to just ignore.....if i knew the OCZ booster helps i would get one....but still no real information if it would affect VTT..
Also, you don't want to use a DDR Booster with high voltage memory and a VDIMM >~3.65V, as the Booster will begin to fluctuate VDIMM a great deal between idle/load above that range. For ~3.8V under load I needed a good ~4V at boot with a Booster, and the loaded voltage fluctuated.
Well? Any ideas? Im still waiting for the sample regulators to arrive.
EMC....
Been thinling about this.
I really think the key to the droop is the fact that Vref is a simple voltage divider, 10ohms/10ohms and then this is used as the reference for the 9173.
The instantaneous current draw on Vref could cuase a slight dip on Vref that is being seriously amplified by the 9173 and is seen amplified on the Vtt output.
Riddle me this batman. What if we instead used 10K/10K resistors on the dividor, and cut the Vref supply connection from the divider-junction and instead tied it to the Vtt output of the 9173?
Vref = Vtt supposedly anyway, and they are driven from the same point on boards like the NF7-S, so it is no something forbidden.
That way there is NO current component to the voltage divider (our reference point for generating 1/2Vdimm) so it should be totally stable. And Vref/Vtt get plenty of juice and I think the "droop" will vanish.
I think the divider and how it is being used was a nice $$-cutting trick, but it is introducing a dip that gets amplified to a droop by the 9173. A way to see if the divider is involved at all is to put a .01uf cap between the divider Vref point and ground...right at the resistor junction. Your measured "droop" should be reduced somewhat.
Thoughts?
I would suggest you go back, look closely at the scope captures in posts #62 & #75, and rethink bro ;) One of them also answers your pondering regarding 256x2 versus 512x2 in that other thread...Quote:
Originally Posted by uwackme
Other thoughts:
- Vref fluctuating with Vtt would tend to make matters worse, not better. It isn't a reciprocal relationship.
- A good half dozen filtering options on all three inputs to the RT9173A have already been through the dungeon - net result zero.
- Temp has a larger effect than filtering, but it does not solve the problem, only lessens it slightly (the RT9173A being next to the Vmem FETs and sharing the copper Vmem plane doesn't help with this one when using BH/CH memory either)
Have decided that between the slow boat, part availability issues, and my present (excessive) work load and other commitments to dump option A and have gen'd up something that'll allow options B or C -- fixing the RT9173A's tracking under load (if it can be and isn't a pure OC throttle problem) or completely replacing it if it can't. But it's something that isn't wired in easily without a PWB due to packaging (25mil spacing) so one is in process. ETA 2-3 weeks.
BTW, based on currently available pics of the "next rev" DFI board, they still are using the same VTT regulator :rolleyes:
Good luck on your boat shipment and let us know how it works out when it arrives bro.
Peace :toast:
Welp i did the mod today at tonys urging..
here are some pics of my handywork.. i jacked the jump idea from tony as it allows for easy removal of the mod..
I have yet to mess with it, but i hope it helps out.
Nice job. Did you gain stablity after the mod? How's the vdimm working out?Quote:
Originally Posted by MaxxxRacer
From the earlier posts, I understand that this mod will shift the vtt "profile" up a little, reducing the effect of the downward swings, right?Quote:
Originally Posted by MaxxxRacer
But what types of users will this help? Those using TCCD? BH-5? Only overclockers? One poster in this thread said his experience was that over time he needed to increase vdimm on the TCCD from 2.8 to 3.1 over time. Will this mod help with issues like that?
Well both my TCCD and UTT is borked right now so I reallly cant comment on either one being more stable, but it does allow for VERY fine adjustment of hte VTT and VDIMM. I used a 20k pot on the VTT becasue i iddnt have a 10k, and it allows me .0001 adjustment resolution, which is even further than my multimeter shows.
As to the vtt, I have it boosted about .01 volts or so. when i get my UTT and TCCD back from RMA I will let you guys know how this mod works out.