- AsRock PG-1600G PSU (ATX 3.1)
- came with dedicated 12VHPWR cable, which I used for the GPU
- I also connected the motherboard’s supplemental PCIe_PWR to the PSU
- MSI X870E Carbon Wifi (latest 1A8 bios)
- 9800X3D
- Asus TUF RTX 5090
- GSkill Z5 6000 CL28 EXPO Ram
- Samsung 9100 Pro M.2
The steps to undervolt the GPU are simple, but require a bit of context:
1. At Stock settings, run MSFS with HWInfo open
With MSFS under full swing, jot down the GPU Max Voltage, and Max Effective Clock values. Then do the same for any benchmark software you want. For me the max values were roughly 1.1 V, and 2950 MHz, sometimes as high as 3000 MHz. This is the speed your card runs at under full load:
2. Shift the GPU's VF curve
Since my card is Asus, I use Asus GPU Tweak III (but I think MSI Afterburner is similar).
First pick the point on GPU VF curve for your Max voltage, Minus 5 or 10%. Example, with my Max 1.1V or 1100 mV, I would cap at 1000mV, a 10% reduction. I pick the point on the curve at 1000mV and flatten everything to the right, down to the same frequency. In my case the selectable point was at 1010 mV but that’s fine, I might even adjust to 1020 to have a bit more power available…
(online videos show capping at 900 mV but that’s just maximizing undervolt, and you would loose performance in MSFS - the goal is just shaving off just that top edge of heat and power draw, but not too much. You don’t want to starve the GPU of voltage when it needs to boost for spikes MSFS)
Then you select the “Active VF range” - which is basically everything from 820 mV to the right. You shift that line up by about 150 or 200 MHz, ideally so your 1V is just above the Max MHz from step 1. In my case, I moved the curve up 225 MHz, so 1V = 2992 MHz. This means for each frequency, you’ve reduced voltage by about 10%.
Save, and test. The reason for not shifting the whole curve is that you don’t want the idle frequencies higher, that creates new issues with no benefit.
3. Memory Clock (data rate)
In both GPU Tweak and MSI Afterburner, there is the ability to increase the Memory Speed, which I think is better described as “data rate”.
The numbers can be a bit confusing, you may see 7000, 14000, or 28000, all basically indicating data rates of the DDR7 (double data rate) memory. I ran GPU Tweak’s built in OC Scanner, which finds the safe / recommended value, which for me was to add 400 to the default of 28002, resulting in 28402 MHz. I believe this is the same as adding 200 to 14000, or 100 to 7000 … but this is where MSI Afterburner and GPU Tweak settings may not be 1 to 1 equivalents, so I’m not sure what works in MSI Afterburner). I found MSFS didn’t like anything more than what I added, but is stable at 28402.
4. Enhance Overclocking Range OFF
A lot of people recommend increasing voltage sliders, or in GPU Tweak there is an option to “Enhance Overclocking Range”. As soon as I tried that, MSFS was unstable. I don’t think there is any need or benefit, and I’m not really sure what it does, so I keep it at stock.
Results...
Here are 2 screenshots from MSFS, at stock, and after tuning, in the A330 over NYC, on a single screen, 4K, DLAA with Ultra settings, “Few Clouds” preset (because clouds have a big impact, I included them). The resulting voltage is about 10% lower, and the “Max Rail” power is also lower (this is the spikes). The improved frametimes etc are mostly about motherboard RAM, the GPU undervolting is really about power saving and room for boost spikes. Note: even with the 1V cap, it will actually go a bit higher when it wants, it must have a “PBO-like” NVIDIA algo that understands basically what you want, but it knows its safe to go a bit further when it wants.
It seems the normal power draw is quite reasonable, so an increase from 364W to 454W isn’t my concern - the benefit (for me) comes from the Max Rail power no longer spiking to 800+ Watts.
The tests were with 1 screen, no max frames or frame gen. In practice I’m flying with 3 screens. Although TAA still looks better to me in the cockpit, DLAA looks way better on scenery details like light poles, thin trees, etc, so I’m using that for now. The 2 side screens are at 2K as I am keeping my TLOD higher. That’s my current compromise.
(That will leave the rest of us in his dust!)
