The biggest disappointment is spending hours assembling a new PC and not getting the performance you see in online benchmarks. The reason is that every PC is configured differently, and you have to set up each component to perform at its best before you get the advertised performance.
Unfortunately, some of these changes can be hard to find. Sometimes, they live in the firmware or require manual configuration, making you wonder why your PC isn’t performing as it should, which is exactly why I make these four changes to every PC.
Turn on XMP or EXPO
Without it, your kit runs at a safe default instead of the speed you paid for
Installing RAM isn’t a mere plug-and-play operation. By default, memory runs at JEDEC baseline speeds, which are well below the kit’s rated speed. To get the advertised speeds, you will need to enable XMP/EXPO, depending on your CPU, and the usual rundown looks like this:
- Open BIOS by pressing F2/Delete (or the key applicable for your motherboard).
- Go to Advanced Mode.
- Look for memory-related menus and choose XMP for Intel CPUs or EXPO for AMD CPUs.
- Now, enable XMP 1/EXPO 1 to get the actual intended clock speeds from your RAM.
Depending on your motherboard, XMP/EXPO profiles may differ and aren’t interchangeable. Profile 1 is the rated profile, whereas Profile 2 is an alternative, and everything else is experimental and may vary by motherboard.
Also, if your motherboard has four DIMM slots, populate only two, because filling all four can cut speeds by 36% on certain CPUs. This is because it crowds out the dual-channel configuration: two RAM sticks would have to share one channel, and the other two would share the second.
For a two-DIMM-slot motherboard, sticking two RAM sticks in either slot works fine. For four-slot boards, check the manual before installing RAM randomly, but the usual recommendation is to populate the second and fourth slots for a dual-channel configuration.
Enable Resizable BAR
The CPU can reach all of your GPU’s VRAM instead of 256MB at a time
A CPU usually accesses VRAM in small chunks, 256MB to be precise. Resizable BAR removes this limit, lifting the restriction on how VRAM flows to and from the CPU. This significantly improves gaming performance, allowing assets and textures to stream faster.
On some modern systems, Resizable BAR may be enabled by default, but another setting also affects VRAM bandwidth: Above 4G Decoding, and Resizable BAR is an extension of this BIOS setting. To turn on Above 4G Decoding and check Resizable BAR, follow these steps:
- Open BIOS at startup.
- Go to PCI Subsystem Settings.
- Find Above 4G Decoding and enable it.
On some motherboards, Resizable BAR may only appear after you enable Above 4G Decoding, so when it does, enable that setting.
To verify whether Resizable BAR is enabled, open GPU-Z → Advanced Tab → PCIe Resizable BAR, then check if the setting has been turned on.
Use the M.2 slot wired to the CPU
Chipset-routed slots share bandwidth with USB, SATA, and everything else on the chipset
Inside your PC, communication pathways called lanes let your CPU or motherboard talk to components. Some lanes connect directly to the CPU, while others route through the motherboard’s chipset.
The motherboard’s chipset can be congested, and if you’re using a high-speed component routed through it, you may experience slower speeds.
For NVMe SSDs, pick the slot closest to your CPU on the motherboard (check your motherboard’s manual, since layouts may differ across models); it is usually connected directly to the CPU, while the rest are routed through the chipset.
The direct M.2-to-CPU slot has only x4 lanes, while the chipset-connected slot shares x4 lanes among the NVMe, other small connections like add-in cards, and the USB ports.
In a PassMark benchmark, a Samsung 970 EVO running at PCIe 3.0 showed a 25.2% loss (79.96 MB/s vs. 106.83 MB/s) when using the chipset-routed M.2 slot instead of the CPU-routed M.2 slot under 4K random QD1.
Populating the CPU-linked M.2 might disable SATA ports or drop the GPU slot to x8 in some configurations with many components installed.
Check your GPU’s PCIe link
A card can fall back to x8 or x4 without any warning
Sometimes, your GPU might not perform at its intended speed even if the software side is fine. This rare issue usually happens when the GPU’s link speed drops.
If your GPU isn’t working like it’s supposed to, download GPU-Z and check the Bus Interface section to see its rated link speed and the one it’s currently at.
Under there, you’ll see something like PCIe x16 4.0 @ x4 4.0. The part before @ is the maximum link your GPU supports, and the part after is what it’s running right now.
If your GPU is running at a lower link speed than it should, move it to the first slot if you have two, since the first runs at x16 and the second at x4. Otherwise, the link speed reduction is due to extra add-in and M.2 cards, so try removing them to see if the link speed returns to x16.
In other cases where you have upgraded a GPU, you might need to run DDU to wipe out previous settings before going in with the new card or cleaning the port.
Some GPUs might lower their link speed when idle, so wake them up by running a benchmark or playing a video game before opening the reading.
Motherboard defaults are tuned to boot reliably, not to perform at their peak
As someone who’s been into PC building since childhood, I’ve noticed that your motherboard will always prioritize compatibility over performance, which is why the PC doesn’t run at its maximum capabilities right out of the box.
Some of these settings aren’t talked about much and come from personal experience — problems I’ve run into when assembling a PC for myself, a friend, or someone from my family. They take a few minutes to configure, and the performance upgrades are double-digit for any sort of demanding workload.