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Hardware Hacking The hammer and tongs school of Overclocking. (NOT for the beginner and you assume all risks)


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Old 24th December, 2006, 05:30 AM
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DIY volt-mod guide

Alright, this guide is for those who would like to vmod their graphics cards/mobos but don't know where to begin. This method works in most cases, but sometimes there are obstacles like overvolt protection etc... so try it at your own risk. This mod will void your warranty. If anyone has suggestions please say so and I'll update the guide.

Materials needed:
- Multimeter

- 2B pencil
OR
- 2x variable resistors, some wire, and a soldering iron w/ solder


1. First, find the voltage regulator chips. On graphics cards these are usually on the back, and on mobo's look near the component you want to mod - e.g. for a vcore mod look near the CPU. These look like black rectangles with lots of silver pins sticking out the side.
http://home.iprimus.com.au/casadelmare/luke/14.jpg
On top of these chips you will find codes such as RT9259, ISL6522, etc. Look for codes beginning with the letters HIP, SC, LM, RT, ISL and ADP. Google these codes, and you should be able to find PDF product sheets - if not, try a different chip. The correct chips usually have the title "Synchronous Buck PWM Controller" or something to this effect. If you're modding your gfx card, there will be one for vgpu and one for vmem (often both use the same code), or sometimes there is one chip which controls both, but I'll get to that in a sec.

2. Once the correct chips have been located, look through the product sheet for a pin layout diagram. Locate the FB (feedback) pin. By reducing the resistance between this pin and ground, the relevant voltage (vgpu, vcore, vmem, etc.) will increase. Sometimes there are FB and FB2 pins; in this case one controls vgpu and the other vmem. Anyway, you can do the mod in one of two ways:

a) Find a resistor connected between the FB pin and ground, and shade this resistor with your pencil (this reduces the resistance).

OR

b) Attach a variable resistor between the FB pin and ground, and reduce the resistance by adjusting the dial.

The choice is yours. VR mods allow greater increases in voltage and give better granularity, but you need some soldering skills to be able to attach wire to those tiny pins. Also there's the problem of where to put the wretched things so they don't fall onto your card and short it out.

3. a) If you chose the pencil mod, get your multimeter ready, and measure the resistance between the FB pin and some nearby resistors (with computer turned off). Once you get a reading of 0, this confirms that the two points are connected. Now measure the resistance between the opposite end of this resistor and ground. If you get 0 again, this is your magic resistor. Shade it and voltage should increase.

b) For the VR mod, measure the resistance between the FB pin and ground. Multiply this value by 20, and get a VR with the resultant value (or a little higher). e.g. If the resistance is 624 ohms, 20x624=12480, so get a 15k ohm VR. Now attach the VR between the FB pin and ground with your soldering iron and some wire.
http://home.iprimus.com.au/casadelmare/luke/vmod/05.jpg
Set the VR's to maximum resistance, and gradually decrease it for increased voltage.

Please Note: Voltage adjustments should always be made with the power turned off to avoid damaging components.

If you're doing a gfx card mod, you'll need to figure out which chip controls vgpu and which controls vmem. If both chips have the same code, just measure the resistance between the FB pin and ground - whichever has the greater resistance will most likely be the vgpu mod, since gpu voltage is lower than vmem voltage most of the time. If the chips have different codes, just do the mod and figure it out after - more gpu voltage allows greater gpu clock speeds, and vice versa.

Now for the voltage measurement points. On mobo's, just use speedfan or BIOS to monitor the voltage. On gfx cards, look for some inductors on the front of the card - these are usually donut shaped with copper wire wrapped around them. Look underneath the card for the two inductor pins, and measure the voltage between each pin and ground. If you get a value close to what the vgpu/vmem should be, this is your measurement point. Generally the inductors are close to the voltage regulator chips, and so you can determine which chip controls vgpu and which controls vmem by looking at the nearby inductor voltage.

If the inductors don't give you the correct voltages, you can use a formula to figure it out:

v(new) = v(stock) x [ r(stock) / r(new) ]

The resistances are measured between the FB pin and ground. To find the stock voltage use google.

If you want to check the maximum voltage for your RAM, google the codes which are on the RAM chips, and look through the product sheet for a 'maximum safe voltage' rating.

Well that's all I can think of for now. To see this method in action, have a look at the 7600GS volt-mod guide, which uses the variable resistors. Good luck and enjoy your volt-mods.
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Last edited by phatic; 29th December, 2006 at 08:17 AM.
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Old 24th December, 2006, 06:40 AM
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Very nice guide.

I'm not one to volt-mod, so I'll give it a pass. However, I know there are probably others who will find this guide useful.

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Old 24th December, 2006, 07:47 AM
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Front page:
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Thanks!
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Old 24th December, 2006, 08:57 AM
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Nice mod...

Nice write up.

I think I will give it a go. What warranty. We don't need no stinking warranty's.
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Old 20th January, 2007, 03:50 AM
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Is there a specific vmod guide for XFX 7900gt/gs, which is the 1st picture in the guide. Alternatively, I'll appreciate it greatly if can get some help vmodding my xfx 7900gs.
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Old 30th January, 2007, 08:54 PM
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uhh you could do the bios vmod.....
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Old 17th February, 2007, 06:18 PM
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hi there, i've done a couple of vmods on gfx cards from guides but i'm very interested in making my own mod for my mobo, the mobo is one that doesn't appear to have had any publicity for vmods so being forced to do it from the beggining.

i'[ve found the voltage regulator and even a spec sheet for it, but it doesn't describe the feedback pin
intersil.com/data/fn/FN9153.pdf
isl6612cb, there appears to be 4 next to the cpu, would it make a difference for which one to mod? and where would i ground it? (i've followed very specific guides for my other mods so not really sure about this)
any help would be appreciated, thanks
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Old 17th February, 2007, 06:38 PM
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Welcome to AOA elfy! Just out of interest - which motherboard do you own?
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Old 17th February, 2007, 07:13 PM
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thankyou for the welcome
it's a sapphire 580 skt 939 i'll take a pic of the vrms when i can find my damned camera :S

edit: btw love the "Have BMX, will travel"
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Old 17th February, 2007, 08:32 PM
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Why thankyou T'is one of the perks of being a subscriber around here, that and free biscuits, though I've yet to see those myself

Pic will be good, we have a few people here who should be able to help you
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Old 17th February, 2007, 08:38 PM
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Quote:
Originally Posted by elfy
i'[ve found the voltage regulator and even a spec sheet for it, but it doesn't describe the feedback pin
intersil.com/data/fn/FN9153.pdf
isl6612cb, there appears to be 4 next to the cpu, would it make a difference for which one to mod? and where would i ground it? (i've followed very specific guides for my other mods so not really sure about this)
any help would be appreciated, thanks
Getting ready to go to the movies. I'll be happy to help you with this once I'm back.

What you've posted is not the voltage regulator; it is the mosfet driver IC.

The driver ICs are all 8 or 10-pin packages. The voltage regulator will be something more like a 28 or 32-pin package, but it will be in that same area. If you can arrange it, a pic (at the highest resolution you can manage) of the PC board in the immediate are of the IC would be helpful as well.

Last edited by Gizmo; 17th February, 2007 at 08:39 PM.
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Old 17th February, 2007, 10:18 PM
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Welcome elfy...

Gizmo will get you sorted out....
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Old 18th February, 2007, 08:32 AM
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right the silly camera has decided to vanish and doesn't wanna come out, i do beleive i've found it now though, intersil.com/data/fn/fn9084.pdf isl6559crz i'll get a photo as soon as i found the begger to aid you in your aiding of me O.o
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Old 18th February, 2007, 11:14 AM
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BTW, use the "go advanced" button, then "manage attachments" to post up photos...
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Old 18th February, 2007, 12:09 PM
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thanks for the hint
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Old 18th February, 2007, 12:55 PM
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Pin 10 is the Feedback pin, and pin 12 is the output from the internal voltage error amplifier. Pin 13 is the remote voltage sense input. Pin 8 is an offset pin. There are a few ways that this circuit could be modified in order to generate an offset voltage for a vmod, and which one to use is going to depend on how the circuit is set up.
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Old 18th February, 2007, 01:55 PM
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right once i've found my cam i'll take a pic of the surrounding area. thanks for all the help
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Old 18th February, 2007, 09:21 PM
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right having trouble finding my camera, but if i'm reading things right all i have to do is attach a wire between the fb-a vr-ground, start off with max resistance and gradually reduce it whilst monitoring the voltage?instead of soldering (whilst i'm rather manky at, hence my fried 1900xtx) would hot glue be ok as long as the wire was attached it should be fine yes? i can just use the case as ground can't i?
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Old 19th February, 2007, 11:03 AM
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Hot glue will not be able to hold the wire in position sufficiently to maintain good electrical contact.

Theoretically, yes, you can tie a pot between the FB and rgnd pins, but if you do that, it is on your head. Without knowing the circuit configuration, I'd hate to tell you to go that route, as you could end up hurting your voltage regulation. I don't <THINK> you would blow anything up, but you could make the system unstable.
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Old 19th February, 2007, 11:42 AM
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right, still waiting for the blooming camera to turn up once it does i'll be back with a photo
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