Wanted: 875P-T volt mods

[MikeyLikesItSI]

I've heard the the droop mod is similiar to another board, but i'm more interested in a VDD/VAGP mod. I wanna push this little watercooled northbridge :-)

Thanks guys

[persivore]

Can you post some pictures of the northbridge/AGP area please.

[MikeyLikesItSI]

http://community.webshots.com/photo/200815446/200819871NBJJxH
http://community.webshots.com/photo/200815446/200819101lntoPB
http://community.webshots.com/photo/200815446/200819174jjkHRc
http://community.webshots.com/photo/200815446/200819269nmJemf
http://community.webshots.com/photo/200815446/200819330IHPIdj

I took these pics when i first bought this board. If you need more, let me know.

Make sure after you click on each link you scroll down to the bottom and hit view full size.

[persivore]

Can you tell me what is written on the chip I have circled please.
http://www.drunken-student.co.uk/tom/mods/200819101lntoPB_fs.jpg

[Thickbrit]

It says...

ISL
6537CR
N41OWF

Thanks,i'm interested too.

[persivore]

The ISL6537 contains 4 voltage regulators, so it is probably controling Vdimm, Vtt, Vagap and Vdd. Can you check the voltage at the points I have marked please. Be careful not to short anything if you measure the voltage at the pin I marked on the ISL6537.


http://www.drunken-student.co.uk/tom/mods/200819269nmJemf_fs1.jpg

[MikeyLikesItSI]

ok, you want me to check the voltage on all of those to ground? or from the pin to the fets?

[persivore]

All of the points to ground.

[ed.howell]

I am interested also!!

Thanks Mike for checking this out!!

Ed

[MikeyLikesItSI]

Persivore: This is with the following bios voltages: vcore 1.500v, vmem 3.0v, vagp 1.8v

http://community.webshots.com/photo/265628712/300838336BfdpQf

PS- Trying to do that with fully sinked mosfets truly sux... :D

[CaTalyst.X]

wooo...persivore this one is over my head :) Only thing i can decipher is that FB4 is for vddq. But i can definately see that it at least controls vDDR and vTT, as well as vddq. However, i dont belive it controls vagp or vdd

-CaT

[CaTalyst.X]

Damn i wish i had one of these boards to mess with......im almost certain that the Intersil chip mentioned above controls vddr, vtt, and vddq, but i dont think it has anything to do with vdd or vagp. What is written on the 8 pin and 14 pin ics near the NB and right next to the ICS PLL chip. Thanks

-CaT

[edit] sry dbl post

[MikeyLikesItSI]

vddr, vtt, and vddq

I'm not up to date on all my abbreviations. What do these stand for?

[persivore]

I'm not up to date on all my abbreviations. What do these stand for?

Vddr is the RAM supply voltage, Vtt is a voltage which is supposed to be 1/2 Vdimm and I don't know what VDDQ is.

Can someone check if the voltages which read 1.8/1.79v etc change when you change the VAGP voltage.

[MikeyLikesItSI]

I'll give it a shot when i get home from work later. BTW, i forgot to mention i had to take those voltages with my vid card out. Would that mess up the results?

[persivore]

ok, thanks. It should be ok without the GFX card in.

[CaTalyst.X]

im not sure what vddq is either, but its a reference voltage on vid card for vgpu. as in vddq = 1/2 vgpu.

[EDIT] Oh yeah i mentioned it because it was on the datasheet, and i think it definately controls vddq, but i dont think it needs modding.

-CaT

[MikeyLikesItSI]

all pins that had ~1.8volts, changed to 1.5v when bios was changed to 1.5v

[persivore]

Feedback 3 (pin 18) on the ISL6537 is the mod point for the Vagp mod. Can you get some resistance readings between pin21 and pin 18, and pin 18 and gound please. I will post a picture of the pins later when I have more time.
http://www.drunken-student.co.uk/tom/mods/200819269nmJemf_fs.jpg

[BB mods's]

Keep up the good work! My DFI875p-t get's here soon then i can help out :)

[MikeyLikesItSI]

persivore: I'm assuming that the VAGP is the only way to up the chipset voltage... should i be concerned about the AGP slot and video card with 2.0-2.1 vagp?

[persivore]

I'll work on the Vdd voltmod after the Vagp voltmod has been worked out otherwise I'll get confused. 2v Vagp should be ok for benching, but I wouldn't run that high 24/7.

Edit: this is the link I was going to post in my above post:
http://www.drunken-student.co.uk/tom/mods/200819269nmJemf_fs.jpg

[MikeyLikesItSI]

ok, this is the deal. I've noticed that a VAGP of 1.8 really helps stabilize my board/memory at 270+ FSB. at around 280, i start to produce memtest errors but only in test #7. i don't produce any on test 5 until 285 or so. I've also noticed that when i have the cover off the side of the computer, if i shift around the water block on the northbridge (unseat it slightly) it will start to error test #7 like MAD. I'm on the theory that heat(now under water)/lack of volts to the northbridge is whats causing errors in test #7. In the bios, VAGP is the only way to increase chipset voltage. if the VAGP/VDD are tied together then i have no choice but to up them both, but what i'm ultimatly after is the voltage to the northbridge/memory controller. If i'm completely off in my theory, please let me know, and maybe we can figure out something to solve my problems, if there is a solution that is.

EDIT: I was hoping to avoid installing a pelt on the NB, as i'm not ready to introduce insulating and an additional power supply. That, and i've never pelted anything before :rolleyes:

[persivore]

What is the default voltage for the chipset? There should be a seperate supply for the Vagp and Vdd (in theory).

[MikeyLikesItSI]

in bios, the only voltage controls i have are vcore, vmem, and vagp. my options for vagp, are 1.5-1.8. 1.5 being default

[MikeyLikesItSI]

Feedback 3 (pin 18) on the ISL6537 is the mod point for the Vagp mod. Can you get some resistance readings between pin21 and pin 18, and pin 18 and gound please. I will post a picture of the pins later when I have more time.
http://www.drunken-student.co.uk/tom/mods/200819269nmJemf_fs.jpg


Resistance between the 2 pins was 955 ohms.
Resistance between the requested pin and ground was 957 ohms

[shark2]

hi.... :D

yeah...the agp supply and chipset supply are separated likes on abit....instead on asus are the same one :p: ....the default chipset voltage would to be around 1.2V if i don't mistake....check my affirmation that is better :p:



sorry for English :stick: :D

[persivore]

For the Vagp mod, connect a 20k variable resistor between pin 18 (feedback 3) and ground as shown in the picture.

http://www.drunken-student.co.uk/tom/mods/875-T%20Vagp.jpg

[MikeyLikesItSI]

So set it at 20k, and reduce resistance for more voltage? Should i use DMM or can i monitor the bios? Also, should i set the VAGP in bios at 1.5 or 1.8? Last question, will this increase VDD as well?

[persivore]

Yes, set it to 20k, and lower it to increase the voltage. It will be safer to set the voltage to 1.5v in BIOS to start with, but you can change it once you know the mod is working properly. You can measure the voltage in BIOS or with a DMM, but it will be much more accurate with a DMM. This mod should only change the Vagp.

For the Vdd mod, can you check the resistance between the points I have marked and the marked MOSFET pin please.

http://www.drunken-student.co.uk/tom/mods/200819269nmJemf_fsNB.jpg

[MikeyLikesItSI]

Just out of curiousity, the mosfet that i'm measuring the resistance in combination with those pins, before you had me check the voltage on the other leg of that mosfet, may i ask why i'll be checking this leg? (sorry for all the questions, just trying to learn :) )

[persivore]

Just out of curiousity, the mosfet that i'm measuring the resistance in combination with those pins, before you had me check the voltage on the other leg of that mosfet, may i ask why i'll be checking this leg? (sorry for all the questions, just trying to learn :) )

I'm trying to check if the pin on the MOSFET (the 'gate' pin) is connected to any of the MOSFET driving pins on the regulator and which section of the regulator it might be using.

[shark2]

hi......Mikey, then have you tried the vagp mod of pervisore?...it works well?....but, for the chipset voltage is there need also of the vdd mod?....true?.....


....and, pervisore, is known something for this vdd mod? :p:


sorry for all these questions :stick: :)

[Detract]

Is there a vdimm mod for this board yet?

[persivore]

hi......Mikey, then have you tried the vagp mod of pervisore?...it works well?....but, for the chipset voltage is there need also of the vdd mod?....true?.....


....and, pervisore, is known something for this vdd mod? :p:


sorry for all these questions :stick: :)

I've been waiting for Mikey to get back to me on the readings I need to check if the chip might be controlling Vdd.


Is there a vdimm mod for this board yet?
For the Vdimm mod, can someone check the resistance between the points I have marked please.
http://www.drunken-student.co.uk/tom/mods/200819269nmJemf_fsVdimm.jpg

[shark2]

I've been waiting for Mikey to get back to me on the readings I need to check if the chip might be controlling Vdd.


For the Vdimm mod, can someone check the resistance between the points I have marked please.
http://www.drunken-student.co.uk/tom/mods/200819269nmJemf_fsVdimm.jpg


ah well :) .....if I have time I measure them :toast:

however for the vdimm mod see this post of kyosen:
http://www.xtremesystems.org/forums/showthread.php?p=599059#post599059

my friend has made that mod and works well :)

[alinosa]

is no one going to measure?

[CaTalyst.X]

Dont really need to measure since kyosen already found the vdimm mod :P

-CaT

[shadewither]

Any Vdd mod yet?
I covered my whole mb with certain unremovable substance
difficult to scrape the pins now :(

[shadewither]

For the Vdd mod, can you check the resistance between the points I have marked and the marked MOSFET pin please.

http://www.drunken-student.co.uk/tom/mods/200819269nmJemf_fsNB.jpg

I managed to remove the insulation and got some results, could you help again?
pin 9 DDR_VTTSNS ~ = 14K ohm
pin 19 DRIVE3 ~ = 18K ohm
pin 21 DRIVE4 ~ = 18K ohm

I was unable to clean the insulation up, therefore the results may be inaccurate. :(

[persivore]

I managed to remove the insulation and got some results, could you help again?
pin 9 DDR_VTTSNS ~ = 14K ohm
pin 19 DRIVE3 ~ = 18K ohm
pin 21 DRIVE4 ~ = 18K ohm

I was unable to clean the insulation up, therefore the results may be inaccurate. :(
Those aren't the readings I expected :(. Can you try to find the resistance between the MOSFET pin and Drive2 (pin 10) as well please.
Can you also do the same readings for the pins I've marked in this (http://tom.drunken-student.co.uk/mods/200819269nmJemf_fsNB1.jpg) picture as well please :)

[shadewither]

Those aren't the readings I expected :(. Can you try to find the resistance between the MOSFET pin and Drive2 (pin 10) as well please.
Can you also do the same readings for the pins I've marked in this (http://tom.drunken-student.co.uk/mods/200819269nmJemf_fsNB1.jpg) picture as well please :)

It's really weird. This time I got a completely different reading. :confused:
between Drive2 and the marked MOSFET pin is <2 Ohm
between other 3 pins and the marked MOSFET pin is >1G Ohm
(it looks like more reasonable than last time, I think? )
I've tried hard to completely remove the insulation, but resulted in short circuit.

Also took some voltage reading:
BIOS VAGP setting MOSFET&Drive2(read both of them to confirm the reading)
1.5v 4.11-4.13v
1.6v 4.04-4.05v
1.7v 4.02-4.03v
1.8v 4.01-4.02v

I'll try to get some other people to confirm the measurement.

[persivore]

That reading looks a lot more like what I was expecting :). I'll have a look at the regulator's datasheet later and see if I can work anything out.

[shadewither]

I've read hipro5's post about AS8,
http://www.xtremesystems.org/forums/showthread.php?t=50940&page=1&pp=25
and I am wondering what is Vfsb? Does Vfsb exist on 875p-T?

[persivore]

Can you confirm which MOSFET you were taking the readings from - was it the one near the AGP slots or the one closer to the ISL6537?
I think Vfsb is the signal voltage for the FSB, but I'm not sure.

[shadewither]

Can you confirm which MOSFET you were taking the readings from - was it the one near the AGP slots or the one closer to the ISL6537?
I think Vfsb is the signal voltage for the FSB, but I'm not sure.

I took the reading from the one near the AGP slot.

[persivore]

Can you check the resistance between pin 11 (feedback 2) and ground, and pin 11 and the pin on the MOSFET near the AGP slot which reads 1.4v.

Also, does anyone know if 1.4v is a realistic stock voltage for Vdd?

[shadewither]

Can you check the resistance between pin 11 (feedback 2) and ground


excuse me, but how to check the resistance between xxx & ground?

[persivore]

excuse me, but how to check the resistance between xxx & ground?
Put one multimeter probe on the pin, and the other on ground. Use a one of the motherboard mounting screw holes as ground. You can check the resistance with the power off :)

[shadewither]

Put one multimeter probe on the pin, and the other on ground. Use a one of the motherboard mounting screw holes as ground. You can check the resistance with the power off :)

thanks a lot :)
i just made my mb down when doing vdimm mod :mad:
it'll take me sometime to get a new mb and measure it

//EDIT
i planned to do kyosen's vdimm mod, but ruined R385, which leg read low voltage; i guess it should connect directly to pin15 feedback? (the low volt side read 0.8xV with high volt side (vdimm said by kyosen) 3.2xv, bios vdimm=3.2v)

I can conclude that I didn't study Eletronic-Engineering related courses well at all; although my major is Computer Science, not very far away from EE. :(

[shadewither]

the resistance between FB2 and ground is 578ohm
other readings are marked on the pic

is that constant 1.39v Vdd?

[persivore]

For the Vdd mod (I'm assuming that the 1.4v is the Vdd voltage, and I think it is), connect a 20k variable resistor between FB2 and ground. If the pins on the chip are too small to solder to, you will need to find an alternative solder point by probing around with a multimeter to find another point connected to FB2.

[shadewither]

For the Vdd mod (I'm assuming that the 1.4v is the Vdd voltage, and I think it is), connect a 20k variable resistor between FB2 and ground. If the pins on the chip are too small to solder to, you will need to find an alternative solder point by probing around with a multimeter to find another point connected to FB2.

thanks a lot
i‘ll try it

[meke]

anyone tried vdimm mod?

[z1erer [HWLuxx]]

does the vdd mod work?