What is power draw like with such a shunt mod? I would be afraid to fry my motherboard... I've also seen people solder a cable to the shunt and then attach a PCIe 6 pin that way. I assume that then evenly spreads the load between the motherboard slot and the extra cable? (i.e. if you are drawing 80 watts it will be 40 from the slot and 40 from the extra cable)
RTX A2000-X3 | a cool&quiet tripple fan mod for the A2000
- Thread starter REVOCCASES
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Hey @REVOCCASES you posted the video earlier of the guy that added 12v to the back.. im guessing thats without a shuntmodright? just injecting 12v?
No, for maximum powaaaa you need to do the shunt mod on the front and the back of the PCB. The additional +12V cable shall just prevent that you fry your PCIe slot / motherboard
I spent quite some time searching for information online about shunt modding but... it's hard to get some real conclusive answers and fully understand the consequences. Some people add a 5 mOhm resistor only to the top shunt, others do it on both. Other people claim that is "too much" and in stead replace the existing shunt with a 4 mOhm one (also either on only one shunt or on both...) Even with adequate cooling and a beefy motherboard... doesn't the 3 phase VRM of the GPU become an issue? I can't imagine that's designed for 100W+ of power...
I also really don't get the 12V cable mod... sure, in theory now the GPU draws half the power through that cable, but what about ground? Your only ground connection is still via the PCIe slot... And if ground is irrelevant in that case, why do 6 and 8 pin PCIe power connectors contain so many ground pins?
BTW: don't be sad about your 3DMark GPU score... I can't get mine above 6000 no matter what I try...
I also really don't get the 12V cable mod... sure, in theory now the GPU draws half the power through that cable, but what about ground? Your only ground connection is still via the PCIe slot... And if ground is irrelevant in that case, why do 6 and 8 pin PCIe power connectors contain so many ground pins?
BTW: don't be sad about your 3DMark GPU score... I can't get mine above 6000 no matter what I try...
most miners add one 5mOhm resistor in parallel / on top of the front one, AFAIK this is considered to be the "safest" mod that won't fry your GPU and motherboard (this is the mod I did and my card wouldn't draw more than 76W peak during benchmark)
with the other mod which adds 5mOhm resistors on both sides, plus the +12V cable, the A2000 could draw up to 140W and I agree this certainly isn't working well for the VRMs long time... IMHO this is more for overclockers who want to beat @SFFMunkee 's Timespy score, not so much for everyday usage
concerning the +12V cable: you don't need an additional GND cable because the PCIe slot has far more GND pins than +12V
how's your voltage / clock curve looking?
with the other mod which adds 5mOhm resistors on both sides, plus the +12V cable, the A2000 could draw up to 140W and I agree this certainly isn't working well for the VRMs long time... IMHO this is more for overclockers who want to beat @SFFMunkee 's Timespy score, not so much for everyday usage
concerning the +12V cable: you don't need an additional GND cable because the PCIe slot has far more GND pins than +12V
how's your voltage / clock curve looking?
For what it's worth, I've shunt-modded my A2000 (front and back additional 0R005 AKA 5milliOhm) and I'm still using slot-power (albeit from a separately powered riser). I do NOT recommend running this at full tilt (or from slot-power) 24/7 as you'll risk cooking the power circuitry or frying the PCIe slot on your motherboard.
If you haven't shunt-modded, you'll want to keep your frequency/voltage curve fairly conservative (I had max 750mV at 1590MHz) as the power limit is pretty restrictive.
You can always try doing a single 5mOhm shuntmod first, then add the second if you're not happy with the results. Remember that with the mod, and thus higher power limit, it opens up the higher voltages so you can get MUCH higher clock speeds.
As a reference, here's a quick 'n' dirty comparison based purely on my online TimeSpy results:
1650MHz - Average 1505MHz STOCK
1792MHz - Average 1776MHz 1xSHUNTMOD (front 0R005 in parallel)
2145MHz - Average 1961MHz 2xSHUNTMOD (front AND rear 0R005 in parallel)
From memory, I had 750mV on stock, about 975mV 1xSHUNT and 1025mV or something for 2xSHUNT.
If you haven't shunt-modded, you'll want to keep your frequency/voltage curve fairly conservative (I had max 750mV at 1590MHz) as the power limit is pretty restrictive.
You can always try doing a single 5mOhm shuntmod first, then add the second if you're not happy with the results. Remember that with the mod, and thus higher power limit, it opens up the higher voltages so you can get MUCH higher clock speeds.
As a reference, here's a quick 'n' dirty comparison based purely on my online TimeSpy results:
1650MHz - Average 1505MHz STOCK
1792MHz - Average 1776MHz 1xSHUNTMOD (front 0R005 in parallel)
2145MHz - Average 1961MHz 2xSHUNTMOD (front AND rear 0R005 in parallel)
From memory, I had 750mV on stock, about 975mV 1xSHUNT and 1025mV or something for 2xSHUNT.
You can use this handy utility to calculate the difference in power limit. https://github.com/bmgjet/ShutMod-Calculator (please note: this is not mine, and I take no responsibility and make no guarantees to the code/executable provided).
But theoretically, if you halve the resistance on the shunt then you effectively double the limit. Likewise double the value shown in HWInfo or GPU-Z to get the 'true' (still estimated) power usage.
5mOhm (stock) + 5mOhm (mod) = 2.5 mOhm --> 140W (power readings x2)
5mOhm (stock) + 4mOhm (mod) = 2.22mOhm --> 157.5W (power readings x2.25)
My assumption is that the circuitry uses both the front and rear shunt resistor, and averages them (or something similar), hence modding only a single resistor is less effective than doing both.
If you wanted to be more cautious, you could use a slightly higher value resistor (6-10mOhm). I stuck with the 5mOhm as it made it a nice round, easy to calculate number and also was tested and proven.
::EDIT:: I hadn't realised quite how few 12V pins there were compared to GND.
A PCIe x16 slot has only FIVE 12V pins, but SIXTY-EIGHT GND pins! (x8 slots have 37, x4 slots have 21, x1 have 9)
75W / 5 = 15W per pin = 1.25A per pin
140W / 5 = 28W per pin = 2.34A per pin
Interesting.
But theoretically, if you halve the resistance on the shunt then you effectively double the limit. Likewise double the value shown in HWInfo or GPU-Z to get the 'true' (still estimated) power usage.
5mOhm (stock) + 5mOhm (mod) = 2.5 mOhm --> 140W (power readings x2)
5mOhm (stock) + 4mOhm (mod) = 2.22mOhm --> 157.5W (power readings x2.25)
My assumption is that the circuitry uses both the front and rear shunt resistor, and averages them (or something similar), hence modding only a single resistor is less effective than doing both.
If you wanted to be more cautious, you could use a slightly higher value resistor (6-10mOhm). I stuck with the 5mOhm as it made it a nice round, easy to calculate number and also was tested and proven.
::EDIT:: I hadn't realised quite how few 12V pins there were compared to GND.
A PCIe x16 slot has only FIVE 12V pins, but SIXTY-EIGHT GND pins! (x8 slots have 37, x4 slots have 21, x1 have 9)
75W / 5 = 15W per pin = 1.25A per pin
140W / 5 = 28W per pin = 2.34A per pin
Interesting.
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Very interesting information, thanks!
My curve currently looks like this
But during the benchmark it never exceeds 1250 MHz or so... keep in mind I am running with a 97% power limit because my PSU is still causing occasional shutdowns at 100% (a beefier one is on the way from China...)
However Afterburner also never shows the current mV, is this normal?
I assume my B550 Aorus is strong enough to handle the "light" shuntmod without extra 12V cable. Speaking of the 12V cable, I also feel like it's a bit weird to just directly pipe an unfiltered 12V line from your PSU in parallel to 12V from the motherboard that traveled through a bunch of other components and probably has a very different looking ripple profile... I assume GPUs with proper PCIe power connectors don't do this the same way but also apply some filtering before combining all the 12V lines... but I am making assumptions based on electronics 101 courses I took 15 years ago...
Either way I want to first make sure that I don't have a lemon so order of priorites is:
- Get a better PSU
- Apply best possible OC/UV with 100% power limit on GPU
- Install the n3rdware copper cooler
- Hope that the sheer cooler operation temps alone unlock a tiny bit more performance (NVidia often boosts higher at lower temps)
- Then see what's next.
The nice thing about the n3rdware cooler is that it might even allow VRM cooling with some thermal pads... I'll definitely look into that.
My curve currently looks like this
But during the benchmark it never exceeds 1250 MHz or so... keep in mind I am running with a 97% power limit because my PSU is still causing occasional shutdowns at 100% (a beefier one is on the way from China...)
However Afterburner also never shows the current mV, is this normal?
I assume my B550 Aorus is strong enough to handle the "light" shuntmod without extra 12V cable. Speaking of the 12V cable, I also feel like it's a bit weird to just directly pipe an unfiltered 12V line from your PSU in parallel to 12V from the motherboard that traveled through a bunch of other components and probably has a very different looking ripple profile... I assume GPUs with proper PCIe power connectors don't do this the same way but also apply some filtering before combining all the 12V lines... but I am making assumptions based on electronics 101 courses I took 15 years ago...
Either way I want to first make sure that I don't have a lemon so order of priorites is:
- Get a better PSU
- Apply best possible OC/UV with 100% power limit on GPU
- Install the n3rdware copper cooler
- Hope that the sheer cooler operation temps alone unlock a tiny bit more performance (NVidia often boosts higher at lower temps)
- Then see what's next.
The nice thing about the n3rdware cooler is that it might even allow VRM cooling with some thermal pads... I'll definitely look into that.
Very interesting information, thanks!
My curve currently looks like this
But during the benchmark it never exceeds 1250 MHz or so... keep in mind I am running with a 97% power limit because my PSU is still causing occasional shutdowns at 100% (a beefier one is on the way from China...)
your curve looks fine to me, normally you should score about 6200 points setting it to 1600Mhz @ 0,750V (without shunt mod) so I assume your power limit is the culprit...
the motherboard doesn't filter any ripple off the 12V PCIe rail, even if "properly" connected... on the GPU side, the additional 12V cable sits right at the shunt resistor, all other components/circuits come later... the only issue I see with this mod is the stress on the VRMs that are certainly not designed to handle 140W long term, at least not without additional cooling...
Yeah actually after typing that response I realized what my issue was... I had both fan curve and thermal limit at stock... and apparently even if you come within 15C of thermal limit, the card already starts throttling just in case...
My best score with stock fan curve and case closed: 5997
Fan pegged at 100%, top of case removed: 6252
100% power limit (seemed to be fine in 3DMark at least): 6292
And then I got another idea... what if the memory is eating too much of the power budget? My VRAM is stable at +1500 (Matching the RTX 3060) but is this really needed considering the other limitations of this chip?
Reduce Memory OC from +1500 to +1250: 6328
Reduced Mem OC to +1000: 6330
Reduced Mem OC to +500: 6378
Important lesson learned: at these low TDPs, don't exaggerate on the memory OC. Memory also "steals" power budget! I assume this effect is even bigger on a 12GB A2000 like mine.
I still don't really understand why the GPU keeps downclocking during the run though... I would expect it to stay pegged at 1560MHz or so but by the end of Graphics Test 2 it is hovering around 1200 MHz.
Even better news: Also Superposition doesn't trip the PSU anymore at 100% power limit (and my score is up from 3300 ish to 3719). I assume the issue was transient spikes, and the flat freq/voltage curve completely irons those out (the chip can simply not go above 750mV anymore, ever.)
My best score with stock fan curve and case closed: 5997
Fan pegged at 100%, top of case removed: 6252
100% power limit (seemed to be fine in 3DMark at least): 6292
And then I got another idea... what if the memory is eating too much of the power budget? My VRAM is stable at +1500 (Matching the RTX 3060) but is this really needed considering the other limitations of this chip?
Reduce Memory OC from +1500 to +1250: 6328
Reduced Mem OC to +1000: 6330
Reduced Mem OC to +500: 6378
Important lesson learned: at these low TDPs, don't exaggerate on the memory OC. Memory also "steals" power budget! I assume this effect is even bigger on a 12GB A2000 like mine.
I still don't really understand why the GPU keeps downclocking during the run though... I would expect it to stay pegged at 1560MHz or so but by the end of Graphics Test 2 it is hovering around 1200 MHz.
Even better news: Also Superposition doesn't trip the PSU anymore at 100% power limit (and my score is up from 3300 ish to 3719). I assume the issue was transient spikes, and the flat freq/voltage curve completely irons those out (the chip can simply not go above 750mV anymore, ever.)
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