rigvelaNot all RAM detected: checks in BIOS and Windows
Quick answer
If the BIOS total is already too low, start with modules, slots and configuration support. If BIOS sees the full amount, identify what Windows is showing: installed RAM, memory available now, or a graphics-memory limit.
Compare capacity, DDR type and slot count →Installed two modules but only one module’s capacity appears? Compare the BIOS total with Windows first. Then establish whether installed capacity is missing or you are looking at memory currently available. The next step depends on that distinction; do not buy another kit yet.
Checklist as text
You can select and copy this text manually. The list does not mark any checks as completed.
On this page
Identify where capacity is missing
Record the expected total from the module part numbers: for example, 2 × 16 GB means 32 GB. Separately record the BIOS total and installed RAM in Windows. This is more useful than one unlabelled number.
| What you found | What to check |
|---|---|
| BIOS shows less than expected | Check configuration and seating, then compare modules individually.Go to this check → |
| BIOS sees all RAM, Windows shows less | Check installed capacity, OS architecture and edition, then system-specific settings.Go to this check → |
| Installed capacity is correct; available memory is lower | Do not confuse memory available now with installed capacity.Go to this check → |
| No display at all after fitting RAM | Follow startup troubleshooting, rather than comparing free memory in Windows.Go to this check → |
Separate installed, available and graphics memory
In Windows, open Settings → System → About and find installed RAM. Alternatively, run msinfo32 from Win + R and locate installed physical memory. Record the label along with the number. Memory available now changes as applications run; it is not a count of installed modules.
Also check that the number is not from GPU-memory information. Intel explains that Shared System Memory is a graphics-use limit, rather than a permanent reservation. Do not subtract that limit from RAM and conclude that half the memory is missing.
If BIOS detects less RAM
Check exact part numbers, DDR type, supported capacity per module and CPU/board population rules. Your model’s manual determines the slot pair. Do not treat another board’s A2/B2 example as a universal layout.
Shut down and unplug mains power before reseating RAM. If you are comfortable doing this, check seating against the manual and compare modules individually in its recommended slot. Record the BIOS total each time. Disconnect power between changes.
Quick checklist
- Module A alone: slot and BIOS capacity recorded.
- Module B alone: checked in the same recommended slot.
- Both together: installed using this board’s population layout.
- One condition changed at a time, without voltage tuning.
If BIOS sees all RAM but Windows does not
First confirm that you are comparing installed RAM rather than memory available now. Record System type and Windows edition under About, then check Microsoft’s OS limits. For example, the listed 32-bit Windows 10 editions have a 4 GB limit; 64-bit editions have different limits.
Hardware reservations and graphics settings are system-specific. Check the PC or board documentation; there is no single normal reserved amount for every computer. Avoid arbitrary registry, boot-limit or BIOS changes. Moving from a 32-bit to a 64-bit OS requires a separate installation and data-protection plan.
Use the results to choose the next step
If one module repeatedly fails detection in the same checked setup, send those results to support; they are not a final diagnosis. If both are detected separately but not together, provide the slot layout, part numbers and BIOS version. The brand name alone does not identify the cause, and another kit is not an automatic fix.
If reseating leaves the PC with no display, follow the separate RAM-startup guide. The calculator below compares DDR, capacity and module count with board limits; it does not test the condition of a slot, memory controller or module.
Compare capacity and slots with your board
The calculator compares DDR type, total capacity and module count with the board limits you enter. It does not test the condition of RAM, slots or the memory controller; use the BIOS and Windows checks in this guide.
Documentation & sources
These are the documents used in this guide. Check your exact model’s specifications on its support page.
- Microsoft — Windows device information ↗
- ASUS — Installed and maximum memory capacity ↗
- ASUS — DRAM installation and BIOS verification ↗
- Kingston — Desktop and notebook memory support ↗
- Microsoft Learn — Memory limits for Windows ↗
- Intel — Graphics memory on Windows 10 and 11 ↗
- Microsoft — 32-bit and 64-bit Windows FAQ ↗