Check RAM Slots Speed and Part Number Before Buying More Memory
The most returned part in any computer shop is a RAM stick that did not match the machine. Total memory alone is not enough to buy a partner for your existing RAM — you need the type, the slots, the speed and the part number. All four take five minutes to check.
✍️ Technical Anshu🪟 Windows 10 / 11⏱️ The complete RAM picture in about 5 minutes
🎥 Watch the full video — the Memory and SPD tabs of CPU-Z read live, step by step
Ask a shop for "16 GB RAM" and you will be sold something. Whether it fits, matches and runs beside your current memory is a different question — answered by the checks in this page, all of which appear in the video's RAM section. Task Manager counts your slots, the SPD tab of CPU-Z reads each stick's own label data, and one PowerShell command lists everything as text. Do these first and a RAM upgrade becomes the safest purchase in computing.
CPU-Z — SPD tab, Slot #2
Module type / sizeDDR4 — 8 GBytes
Max BandwidthDDR4-3200 (1600 MHz)
ManufacturerExample brand (read yours here)
Part NumberCopy this before you buy
The SPD tab reads the specification chip on each RAM stick — including the part number that makes buying a matching stick foolproof. Panel shows example values.
1
Count Your Slots and See Which Are Free
Open Task Manager (Ctrl + Shift + Esc) and go to Performance → Memory
Read Slots used — for example "2 of 4" means two free slots waiting; "2 of 2" means any upgrade replaces existing sticks
Form factor tells you the physical size: DIMM for desktops, SODIMM (smaller) for laptops — they are not interchangeable
The same page shows the Speed your memory is running at right now and how much is Hardware reserved
One honest caution: some thin laptops have memory soldered to the board. If slots are reported but the sticks turn out to be onboard, no upgrade is possible — the next two checks will make that clear before you spend anything.
2
Read Each Stick in the CPU-Z SPD Tab
SPD is the small chip on every RAM stick that stores its own specification. CPU-Z reads it directly — this is the heart of the video's RAM section:
Open CPU-Z and go to the SPD tab
Change the Memory Slot Selection dropdown — each slot in turn. Empty slots say so
For every filled slot, note four things: Module Size, Max Bandwidth (the rated speed, like DDR4-3200), Manufacturer and Part Number
The Memory tab complements this with the total size, the DDR generation and whether the sticks run in Single or Dual channel
That part number is your shopping list. A second stick with the same part number is the lowest-risk upgrade in all of PC hardware.
3
Check the Speed Your RAM Is Actually Running
Rated speed and running speed are two different facts. On the CPU-Z Memory tab, DRAM Frequency shows the live rate — remember to double it (DDR transfers twice per cycle), so about 1600 MHz means 3200 MT/s effective.
If the doubled figure is lower than your sticks' rating, the memory profile is usually not enabled in BIOS (XMP on Intel boards, EXPO or DOCP on AMD boards). That is a BIOS setting, one careful change — but confirm the numbers here first, because many PCs are already running at full rating and need nothing.
4
List Every Stick with One PowerShell Command
Prefer a text answer you can copy? Open PowerShell and run:
One row appears per stick, with its slot name, speed, maker and part number
Capacity is shown in bytes — divide by 1073741824 to get GB. The value 8589934592 is exactly 8 GB; do not let the long number alarm you
Copy the whole table into a note or message — it is the complete RAM truth of the machine in four columns
5
The Buying Rule — Type First, Then Speed, Then Size ⭐
With the facts in hand, the purchase becomes simple:
Type is non-negotiable. DDR4 and DDR5 sticks are physically keyed differently and a board accepts only its own generation
Match the speed of what you have, or accept that mixed sticks generally run at the slower stick's speed
Use your free slots first; if none are free, replace the pair with a larger matched pair rather than one big stick beside one small one
Prefer the same part number you found in the SPD tab — it removes every compatibility doubt in one stroke
🔍 You rarely need to open the machine to identify RAM. SPD literally means the stick carries its own specification chip — CPU-Z reads that chip through software. Open the cabinet when you are ready to fit the new stick, not just to find out what to buy.
🎥 Watch the Memory and SPD Tabs in the Video
Total RAM, channel mode, per-slot part numbers — the video reads them live in CPU-Z so you can copy the method exactly.
Task Manager says Slots used 2 of 2. Can I still add more RAM?
You can upgrade, but by replacing rather than adding: swap the two existing sticks for a larger matched pair, such as going from 2 x 8 GB to 2 x 16 GB, staying within your motherboard's maximum. First confirm in CPU-Z's SPD tab that both slots report removable sticks — a few very thin laptops solder the memory, and those cannot be upgraded at all.
Why does PowerShell show my RAM capacity as a huge number like 8589934592?
Because that command reports capacity in bytes, not gigabytes. Divide by 1073741824 (the number of bytes in a gigabyte): 8589934592 bytes is exactly 8 GB, and 17179869184 is 16 GB. The figure is precise — it just needs the one division to read like the number on the box.
Can I mix an 8 GB stick with a 16 GB stick?
In most desktop boards it works and gives you 24 GB in total, with part of the memory running in dual-channel (often called flex mode). It is a reasonable budget move. The safer recommendation remains a matched pair of the same part number and speed, which guarantees dual-channel across the whole capacity and removes timing mismatches from the equation.
This guide follows the PC configuration check shown in the Technical Anshu video above • Stuck on a step? Ask in the video comments and the community will help 🙏