By john 
System information shows “8.00 GB (5.88 GB usable)” or a similar gap. When Windows 10 usable RAM less than installed appears, it looks as though some memory has YY PAUS vanished.
Some difference is normal. Integrated graphics borrow part of the system memory, and certain hardware reserves small amounts.
A large gap, however, usually points to a setting, an incompatible module, or an operating system limit.
The gap is easy to spot under Settings > System > About, where Windows lists installed RAM and, in brackets, the amount it can actually use.
Possible Causes
Memory is reported as unusable for these reasons:
- Integrated graphics reserve part of the RAM.
- The maximum memory option is set in msconfig.
- A 32-bit version of Windows is installed, which can use about 4 GB at most.
- A memory module is not seated correctly or is incompatible.
Checking the system type quickly rules the 32-bit limit in or out.
Quick Fixes to Try First
Confirm the basics.
- Open Settings > System > About and check the system type. If it says 32-bit, Windows cannot use much more than 4 GB.
- Press Windows + R, type msconfig, and open the Boot tab.
- Select Advanced options and untick “Maximum memory” if it is ticked.
- Select OK and restart.
- Check the usable memory again.
The msconfig setting is often changed by mistake through online “speed-up” guides.
As a rough guide, a difference of a few hundred megabytes up to around 2 GB on a PC with integrated graphics is normal. A larger gap, or exactly half the memory missing, suggests a configuration or hardware problem.
Advanced Steps for Stubborn Cases
Check hardware and firmware.
- Enter the BIOS and see how much memory it detects.
- If the BIOS shows less than installed, switch off, unplug the PC, and reseat the memory modules.
- Test each module separately to find one that is not detected.
- Check the BIOS for integrated graphics memory settings, sometimes called UMA frame buffer size, and reduce it if set very high.
- Update the BIOS if the manufacturer lists memory compatibility fixes.
If the PC has 32-bit Windows installed on 64-bit hardware, moving to 64-bit requires a clean installation of Windows.
Before You Go Further: Keep Your Files Safe
Turn off and unplug the PC before touching memory modules, and discharge static by touching metal. A clean installation erases data, so back up before switching to 64-bit Windows. Buy memory that matches the manufacturer’s specifications.
Conclusion
Some memory reservation is normal, but large gaps usually have a clear cause. Check for 32-bit Windows, remove the msconfig limit, and make sure every module is detected.
When the full amount is finally reported, open Task Manager’s Performance tab and check the memory section, which also shows how many slots are in use and the speed at which the memory is running.