GTX 275 Lightning Vmods
 

Everywhere I've searched just describes BIOS/software hacks. That's great, but I prefer dynamic tactile control with screw turns.

The card uses uP6208 and the FB is simple to map with a nice solder point. Vmem is also straightforward.

OCP is available for modding with the IMAX2 pin and a 100K VR should work over the existing 36K resistance from pin to GND.

Here's my question. Is it reasonable to add a capacitor in series with the added OCP VR? If it is, how should I choose a capacitor value? 2.5V? Low or high uf?

This description of IMAX2 pin from the data sheet made me think of it:
Output current of IMAX2 is proportional to total load current. Connect a resistor between IMAX2 and GND then the voltage of IMAX2 is proportional to total load current. If IMAX2 voltage is higher than 1.2V, OCP will be triggered. Resistor between IMAX2 and GN?D can adjust OCP level. Capacitor between IMAX2 and GND can filter load current ripple to avoid OCP mis-trigger.

so 1.2 volts is the point where ocp kicks in... I would think 2.5 should work fine.. no clue on how high of a capacitance to use... maybe OCGMJ or the Pizzaman could enlighten us.. Shouldn't need much though. Maybe even a little farad capacitor could do the trick... :Dizzy:

I decided to screw the capacitor. Since I haven't done squat for benching lately, figured I'd post some pics of the vmods I did tonight on this card.

Thank you MADSHRIMPS for posting vmem mod in your 275 lightning review!

Turns out the gpuv and ocp mods are basically the same as gtx 260, but I mapped out the 275 lightning pathways.

I'll try to test tomorrow........

http://img838.imageshack.us/img838/4...gpuvandocp.jpg

http://img231.imageshack.us/img231/9...htningvmem.jpg

Someone is preparing for 3dmark2001 SE :D

Give 'em hell Patch !!!

Will do my best Sofos! This is my back burner project to snuggle up to on some cold night.

The mods work. Only pushed vgpu to 1.34v..

Card seems like a decent one. Not stellar, but it'll be fun. Here's with the GPU under water:

http://img819.imageshack.us/img819/3959/275h2003.jpg

Nice run... with a little more tweaking she looks like a top 20 card. :thumbsup:

gtx 275 ranking

Okie Dokie. :Hi: Now I just need my REX to start tweaking 01 on water. Then some juice.

http://img831.imageshack.us/img831/3959/275h2003.jpg

http://img841.imageshack.us/img841/8279/275h2006.jpg

Can you go over 1.45v with this mod?
Nice work btw!!!

REX shipps tomorrow and than you once again for letting me use it! You are the greatest Shaun! :thumbsup:

Good stuff as always Patch!

So did you VR the OCP or have any OCP troubles at all, yet? I'm wondering what effect just adding a cap to the IMAX connection would yield. I would think 2.5v and not much uf needed.