Your CPU does not run at full speed when it is idle — that would generate unnecessary heat and waste power. Instead, processors use a hierarchy of sleep states called C-States to progressively power down idle cores. Understanding these states is useful for gaming because deeper sleep states introduce latency when the CPU needs to wake up quickly, and in some workloads that latency is measurable.

What Are CPU C-States?

C-States (C for idle) are defined by the ACPI specification and represent different levels of CPU idle depth. Each deeper state reduces power consumption at the cost of longer wake-up latency:

State	Name	Typical Latency	Power Reduction
C0	Active	0 (running)	None — CPU is executing
C1/C1E	Halt	<1 µs	~10–20% per core
C3	Sleep	~50–150 µs	~40–60% per core
C6	Deep Power Down	~200–400 µs	~85–95% per core
C8	Enhanced Deep Power Down	~400–800 µs	~95%+ per core
C10	Deepest Rest (Intel only)	>1 ms	Near-full shutdown

Not all CPUs implement all states. Intel 13th and 14th generation desktop CPUs typically support through C10 on efficiency cores. AMD Ryzen 7000 series supports through C6 globally and C10 on some configurations.

C1E is a variant of C1 that enables voltage reduction on halted cores — it saves slightly more power than basic C1 but has nearly the same wake latency.

How C-States Affect Gaming Latency

In a running game, cores are rarely perfectly busy 100% of the time. There are brief gaps — waiting for GPU completion, waiting for audio, waiting for network packets — during which the OS may allow a core to enter a low-power state. If the game thread wakes suddenly (a physics event, a game loop tick) and the core is in C6 or C8, the 400–800 µs wake-up penalty adds to frame time variance.

For most games running at 60–144 Hz (frame budget of 7–17 ms), C-State latency is a small fraction of the frame budget. The impact shows up in 0.1% lows and in rare frame time spikes rather than average FPS.

For games with very tight frame budgets — competitive play at 240+ Hz where each frame has a 4.2 ms budget — C-State wake latency becomes a non-trivial fraction of available time.

Disabling C-States via BIOS

The most complete method is to disable deep C-States in the UEFI firmware:

Reboot and enter BIOS (Del, F2, or F12 at POST).
Navigate to Advanced CPU Configuration, CPU Power Management, or similar (varies by manufacturer).
Look for settings labeled C-State Support, Package C State Limit, or CPU C States.
Options vary by board:
- Set Package C State Limit to C2 or C0/C1 to prevent deep sleep states.
- Or disable C-State Support entirely for the most aggressive approach.
Save and exit.

On AMD Ryzen systems, look for Global C-State Control under CBS (Common BIOS Settings) > CPU Common Options. Setting it to Disabled prevents C3 and deeper states system-wide.

BIOS-level disabling prevents C-States entirely regardless of OS power plan settings.

Controlling C-States via powercfg

You can limit C-State depth through Windows’ power management without entering the BIOS. This approach is reversible quickly and does not require a reboot.

To view current power settings:

powercfg /query SCHEME_CURRENT SUB_PROCESSOR

The relevant setting is Processor idle demote threshold and Processor idle promote threshold. More directly, you can set the minimum processor state to prevent the OS from allowing deep idle:

powercfg /setacvalueindex SCHEME_CURRENT SUB_PROCESSOR PROCIDLEDEMOTE 0
powercfg /setacvalueindex SCHEME_CURRENT SUB_PROCESSOR PROCIDLEPROMOTE 0
powercfg /setactive SCHEME_CURRENT

However, the cleaner approach is using the High Performance or Ultimate Performance power plan. Open Settings > System > Power, or use:

powercfg /setactive 8c5e7fda-e8bf-4a96-9a85-a6e23a8c635c

That GUID is the High Performance plan. To enable Ultimate Performance (which disables C-State promotion aggressively):

powercfg /duplicatescheme e9a42b02-d5df-448d-aa00-03f14749eb61

Then set the newly created scheme as active. Ultimate Performance keeps the processor at maximum state more aggressively, effectively reducing deep C-State entry without requiring a BIOS change.

The Power Consumption Trade-Off

Disabling C-States has real power and thermal costs:

A desktop CPU that normally idles at 5–15 W while in C6/C8 will idle at 25–45 W with C-States disabled.
At the system level, expect 30–70 W higher idle power consumption.
CPU temperatures at idle will rise 5–15°C depending on cooling.

For a desktop gaming PC that runs a few hours a day, this is negligible in electricity cost. For an all-day workstation or a laptop, it is a significant trade-off. Never disable deep C-States on a laptop — the thermal and battery impact is substantial.

Practical Recommendation

For desktop gaming PCs, the recommended configuration is:

Use the High Performance power plan as a baseline. This reduces C-State depth significantly compared to Balanced.
Limit Package C-State to C2 in BIOS if your board supports it. This eliminates the deep wake latency while still allowing mild core idle, keeping thermals reasonable.
Leave C1/C1E enabled — the sub-microsecond latency of these shallow states is imperceptible, and they save meaningful power during the short gaps between game loop ticks.

Full C-State disabling is a valid experiment for benchmarking purposes, but for daily use the C2 limit hits the sweet spot between responsiveness and reasonable power draw.