Inconsistent input feel and lagometer spikes (green+yellow) - day-by-day variation with no reproducible cause

CoD4x CoD4x | Client Support
1

SYSTEM SPECIFICATIONS

OS: Windows 11 Home 25H2 (Build 26200.8524)
CPU: AMD Ryzen 5 5500
GPU: NVIDIA GeForce RTX 3050 6GB (Driver 566.36)
RAM: 16GB DDR4 3200MHz
Motherboard: MSI A520M-A PRO
Monitor: BenQ EX240N 165Hz (HDMI)
Mouse: Logitech G203 250Hz polling
COD4x: Client 21.3 / Server 21.3

GAME SETTINGS

com_maxfps: 125 or 250
r_fullscreen: 1
r_displayRefresh: 165 Hz
cl_maxpackets: 125 or 100
snaps: 30 or 20
rate: 100000 or 25000
sv_fps: 20 (server-side, seems always fixed)

PROBLEM DESCRIPTION

For over 6 months, I have been experiencing day-by-day variation in input feel that I cannot reproduce or resolve consistently and concurrent green and yellow spikes (red spikes some times, but not as usual as yellow/green ones) in lagometer (please see attached picture. I was trying to post more pictures but it is not allowed as I am a new user).

   ![Screenshot 2026-06-08 224749|141x157](upload://irD23NA7leDTQHWRossILzHYV6h.png)

On good days:

  • Mouse input and character movement feel perfectly synchronized (“smooth”)
  • Feewer green or yellow spikes
  • I can react to enemies normally and have competitive performance

On bad days:

  • There is a noticeable delay (per my subjective personal feeling, I have not been able to quantify this) between mouse input and character movement
  • Enemies appear and kill me instantly before I can react (this is very obvious when I play on Shipment or Killhouse: on good days there is a bit moment before I respawn and move. On bad days, I get killed immediately I respawn without a chance to move. On same servers)
  • Many (10-20) yellow and green spikes on a single game

This occurs across multiple servers (NVTS, EBC Promod, and others), ruling out a single server as the cause. Tested on two different PCs and two different ISPs - same symptom. Only common factors I can think of are (1) both PC are Windows 11, (2) with the same mouse and (3) in the same region (20km distance).

LAGOMETER OBSERVATIONS

On bad days, the lagometer shows frequent simultaneous green and yellow spikes.

  • Green spike alone: occurs on both good and bad days
  • Green + yellow simultaneous: occurs predominantly on bad days
  • Yellow spike alone: never observed

Yellow/green spikse appear to happen often for the following cases, but not exclusive (can happen randomly as well)

  • when I shoot an enemy
  • when I encoutner an enemy
  • when I throow a flag or flash
  • when I get killed by killstreak

WHAT HAS BEEN INVESTIGATED AND RULED OUT IN MY OPINION

The following have been tested and confirmed to have no consistent effect:

Hardware & drivers:

  • Two different PCs
  • Two different ISPs
  • Multiple mouse polling rates (125Hz / 250Hz / 1000Hz)
  • NVIDIA driver versions (multiple tested)
  • HDMI vs configuration changes

Windows & system:

  • Timer resolution (confirmed 1.000ms during COD4, normal behavior)
  • GlobalTimerResolutionRequests registry setting
  • Dynamic Thread Priority Boost (disabled via registry)
  • Windows Defender real-time monitoring (disabled via PowerShell)
  • BIOS: Global C-State disabled, ASPM disabled
  • Process priority: iw3mp.exe set to High via Process Lasso
  • CPU affinity: nvlddmkm.sys DPC pinned to CPU11 via registry

Game settings:

  • Various com_maxfps values (125, 250, 333, 0)
  • Various cl_maxpackets values (30, 60, 90, 100, 125)
  • Various rate values (10000, 25000, 100000)
  • Various snaps values (20, 30, 40)
  • DXVK / d3d9.dll
  • Fullscreen optimization disabled
  • r_fullscreen 1

Frame timing (measured via PresentMon):

  • On good days: avg 8.000ms, std dev ~0.928ms, hard stalls ~0.05/min
  • On bad days: avg 8.000ms, std dev ~1.099ms, hard stalls ~0.62/min
  • The average frametime is identical; only consistency varies
  • Hard stall frequency correlates with subjective feel
  • RTSS framerate limiter worsened hard stalls (1.47/min) - abandoned

System diagnostics:

  • LatencyMon: nvlddmkm.sys highest DPC 311-357μs, 0-8 events >500μs
  • No TDR events (Event ID 4101) in Windows Event Log
  • No NVIDIA driver errors in Event Log
  • WHEA errors: 0
  • PCIe error counters: Recovery Count 6 (stable, non-fatal)

KEY REMAINING OBSERVATIONS

  1. Local server (127.0.0.1) always feels smooth - rules out PC hardware
  2. Green+yellow simultaneous spikes suggest snapshot loss, not pure frame drops
  3. The problem is non-reproducible: same settings produce good and bad sessions
  4. No measurable difference in PC-side metrics between good and bad days
    that fully explains the subjective experience
  5. COD4x version 21.3 on both client and server (21.2 showed same symptoms)

QUESTIONS FOR THE COMMUNITY / DEVELOPERS

  1. Is there a known issue in COD4x 21.3 that could cause intermittent
    snapshot delivery failures or client-server synchronization problems?

  2. Could the combination of sv_fps 20 / cl_maxpackets 125 / com_maxfps 125
    cause periodic packet handling issues in the COD4x client?
    (Recommended optimal values for sv_fps 20 servers would be appreciated.)

  3. Is there any COD4x-specific logging or diagnostic tool that could capture
    the exact state during a bad session beyond what PresentMon and LatencyMon
    provide?

  4. Has anyone else reported day-by-day variation in input feel that cannot
    be explained by standard PC or network diagnostics?

I have done all thins I can think of with help from AIs (GEMINI and Claude), but I have a lay-man for PC or PC gaming. Any insight from the COD4x development team or experienced community members would be greatly appreciated. I am happy to provide additional data, logs,
or test specific configurations on request.

Thank you.