Resizable BAR (ReBAR/SAM) Not Enabled
What is this error?
Resizable BAR (NVIDIA) or Smart Access Memory (AMD) is not enabled, preventing the CPU from accessing the full GPU VRAM at once, costing 5-15% performance in supported games.
Common causes
- BIOS setting 'Above 4G Decoding' and 'Resizable BAR' not enabled
- CSM (Compatibility Support Module) still enabled in BIOS preventing ReBAR
- GPU driver or VBIOS does not support ReBAR
- older motherboard BIOS without ReBAR support
How to fix it
- Enable Above 4G Decoding and Resizable BAR in BIOS
- disable CSM
- verify with GPU-Z
Too many steps? Crashless can diagnose this automatically — checks your drivers, temps, VRAM, and 400+ known error patterns.
Get free AI diagnosis Detailed analysis
Resizable BAR (ReBAR) gives your CPU direct access to your entire GPU VRAM instead of accessing it in small 256MB chunks. In supported games, this is a free 5-15% FPS boost. To check if it is enabled: open GPU-Z and look for 'Resizable BAR' in the main window — it should say 'Enabled'. If it says 'Disabled', you are leaving performance on the table. Enabling it requires two BIOS settings and one condition. First, go into BIOS and find 'Above 4G Decoding' (sometimes under Advanced > PCI Subsystem or Boot). Enable it. Second, find 'Resizable BAR' or 'Re-Size BAR Support' and enable it. The critical third step: CSM (Compatibility Support Module) must be DISABLED. CSM is a legacy boot mode and it blocks ReBAR. Find CSM in BIOS (usually under Boot) and set it to Disabled. Your Windows install must be UEFI with GPT partition (not legacy MBR) for this to work — if your system does not boot after disabling CSM, your Windows was installed in legacy mode and you will need to convert it first using mbr2gpt. After enabling ReBAR, reboot into Windows, open GPU-Z, and confirm it says Enabled. Then test your games — titles like Cyberpunk 2077, Fortnite, Assassin's Creed, and many others show measurable gains.
When to seek help
If this error keeps happening after trying the fixes above, it may point to a deeper hardware or system issue. Consider professional help if:
- The crash occurs across multiple games or applications
- You see the same error after a clean Windows install
- Your PC is less than a year old (could be a warranty issue)
- You smell burning or hear unusual sounds from your PC
Or let Crashless do the deep analysis for you -- our AI checks drivers, temps, event logs, and 400+ known patterns automatically.
Chat with AI about Resizable BAR (ReBAR/SAM) Not Enabled
Describe your setup and get a personalized diagnosis in seconds. Free, no signup needed.
Get AI diagnosis Chat with AI about this error
Describe your setup and what you were doing when the crash happened. Our AI checks against 400+ known crash patterns — free, no download needed.
Let Crashless handle it
The desktop app scans your drivers, temps, VRAM, event logs, and 400+ known patterns — then walks you through the fix step by step.
