View Full Version : Foxconn X38A vdroop mod
Misko78
11-24-2009, 04:29 PM
I have a huge "dancing" vdroop ranging from 0,05V to 0,08V. Can some one tell me how to do vdroop mod. Here is a pic of ISL6327.
http://img40.imagefra.me/img/img40/1/11/24/misko78/t_ust33k6nm_9ca0dba.jpg (http://imagefra.me/view.php?img=/1/11/24/misko78/f_ust33k6nm_9ca0dba.jpg&srv=img40)
Thanks. :wave:
http://img407.imageshack.us/img407/9415/g33schemehe7.png
http://img61.imageshack.us/img61/1299/pencilg33mmy3.jpg
This for gigabyte but your will be similar
Misko78
11-25-2009, 04:30 AM
If i got it right i should do pencil mod between 1 and 2?
http://img37.imagefra.me/img/img37/1/11/25/misko78/t_1bjfagj55mwm_cf4d027.jpg (http://imagefra.me/view.php?img=/1/11/25/misko78/f_1bjfagj55mwm_cf4d027.jpg&srv=img37)
Looks like, yes.
I would STRONGLY recommend using VR than "pencil" mods. They are (VR-type mods) much more stable and safe for hardware!
Misko78
11-25-2009, 10:11 AM
Looks like, yes.
I would STRONGLY recommend using VR than "pencil" mods. They are (VR-type mods) much more stable and safe for hardware!
I agree with that. What VR should i use? Is it in a direct function of ohms law, so when i measure it (where) i could calculate it.
Does VR goes in a same place as pencil mod, or somewhere else?
General rule = 10 times more than curcuit resistance. That will get good precision and safe range for change. so check resistance on points 1 2 and put 10 more. For example you measure 4.7kOhm - put 47k.
Does VR goes in a same place as pencil mod, or somewhere else?
Why it need to go another place? Think about principle more, and you get it ;)
Misko78
11-26-2009, 04:40 PM
I managed to destroy original 2,55KΩ 1% resistor while i was soldering. I replaced it with 2,2KΩ which i took from dead SB Live! but i don't if it has 1% tolerance. When i measured vdroop it was around 0,4V so i decided to add a VR anyway. I took 40KΩ one and soldered it in parallel connection (R1xR2)/(R1+R2). Thus reducing resistance to 2,08KΩ. I got 0,2V fixed Vdroop at 1,51KΩ resistance and i think it is good that way. Do i need to lower it more? Is it safe to use resistors with higher tolerance?
http://img40.imagefra.me/img/img40/1/11/26/misko78/t_ust5bwgsm_5b30abd.jpg (http://imagefra.me/view.php?img=/1/11/26/misko78/f_ust5bwgsm_5b30abd.jpg&srv=img40)
Thank you TiN_EOF for guidance ;) :wave:
Misurica
You welcome, I like helping you, you got things correct, without dumb questions "what is resistance, and how to measure it :D".
It's not very neccessary to have 1% there. So you are safe, you can try to tune it little more. 0.2V is quite big droop still, i'd suggest 0.05 ok ;)
Be careful not to short VR to the end.
Misko78
11-27-2009, 05:31 AM
Well thanks for kind words. :up: I've managed to completely remove Vdroop at 605Ω, unfortunately trimmer I've bought is crappy so fine tuning is not possible. With just very very small shift to right i get 9Ω and when i screw it to left i get near 1KΩ. I can't stop asking myself why did I superglued it before everything was measured and set.
Is it dangerous to completely eliminate vdroop on Kentsfield CPU?
EDIT: I made tenfold mistake in previous posts, was talking about 0,02V vdroop not 0,2V.:dammit:
celemine1Gig
12-04-2009, 04:08 AM
Keep in mind that the circuits were designed with droop in mind. So without further modifications, you should leave a little droop.Don't eliminate it completely. It's generally safer for your CPU that way.
Misko78
12-11-2009, 06:36 PM
Keep in mind that the circuits were designed with droop in mind. So without further modifications, you should leave a little droop.Don't eliminate it completely. It's generally safer for your CPU that way.
Finaly i've changed this micro trimmer for >20 turn one. I've stayed with small droop giving me max 24/7 stable OC 3,5GHz@1,45V :( i haven't got much better than previous maximum which was 3,3GHZ@1,32.
Anyway TiN_EOF & celemine1Gig thanks again. Now i have more guts to try to vmod two 3850 cards i have. (http://www.xtremesystems.org/forums/showpost.php?p=4122630&postcount=987)
celemine1Gig
12-12-2009, 05:21 AM
Finaly i've changed this micro trimmer for >20 turn one. I've stayed with small droop giving me max 24/7 stable OC 3,5GHz@1,45V :( i haven't got much better than previous maximum which was 3,3GHZ@1,32.
Anyway TiN_EOF & celemine1Gig thanks again. Now i have more guts to try to vmod two 3850 cards i have. (http://www.xtremesystems.org/forums/showpost.php?p=4122630&postcount=987)
Good to hear that it worked out for you and also good to hear that you exchanged that trimmer. It's easy to kill hardware when slipping, i.e. changing resistance to a very low level by accident, with one of these 1 turn trimmers. The 20 turn trimmers are much more suitable for vmods. You just have better control over the output voltage that way. You could also think about adding a series resistance to keep you safe from short circuiting the feedback circuit. But as long as you are careful with the trimming, you should be alright. Just food for thought.
And 3.5GHz doesn't sound that bad to me. I don't know what chip it is exactly, but not all CPUs can clock to 4GHz easily. If you have a stable 3.5GHz, be happy about that. Just think about what you really need the extra speed for. Normally 3.5GHz should be enough for nearly everything, except for benchmark results. ;)
Misko78
12-12-2009, 06:34 AM
Good to hear that it worked out for you and also good to hear that you exchanged that trimmer. It's easy to kill hardware when slipping, i.e. changing resistance to a very low level by accident, with one of these 1 turn trimmers. The 20 turn trimmers are much more suitable for vmods. You just have better control over the output voltage that way. You could also think about adding a series resistance to keep you safe from short circuiting the feedback circuit. But as long as you are careful with the trimming, you should be alright. Just food for thought.
And 3.5GHz doesn't sound that bad to me. I don't know what chip it is exactly, but not all CPUs can clock to 4GHz easily. If you have a stable 3.5GHz, be happy about that. Just think about what you really need the extra speed for. Normally 3.5GHz should be enough for nearly everything, except for benchmark results. ;)
Well i wasn't trimming while system was up, i measured it with DMM as i lowered resistance by 100Ω 'til i found sweet spot.
Chip is Q6700 G0 so i hoped to get around 3,7 and maybe 3,8. Anyway i'm satisfied with this 200MHz bump, all this was a great experience and very addictive one. ;) I'm modding my 3850s but problem is that i can't find BS-9M EOM datasheet anywhere. :(