The Ultimate RAM Guide : DDR4 vs DDR5, Recommended Capacity, and How to Choose Speed/Clocks

 RAM (Random Access Memory) is the CPU’s high-speed workbench. Programs load their working data into RAM so the CPU can read/write it quickly. With enough capacity and speed, apps launch faster and multitasking stays smooth.


Photo by Athena Sandrini on Pexels

As DDR generations evolved from DDR1 → DDR5, transfer rates, bandwidth, and power efficiency improved.
Before you buy, double-check your motherboard support, capacity needs, dual-channel setup, clock & timings, and brand/QVL.

What RAM Does (and Why It Matters)

When you launch an app, files on your SSD/HDD are copied into RAM, and the CPU works on that data from there.
If the CPU is the brain, RAM is short-term memory - fast, temporary, and cleared when power is off.

  • Capacity = desk size. A bigger desk lets you keep more “open books” (apps/tabs) at once.

  • Too little RAM → the system borrows swap/virtual memory on the SSD/HDD (much slower) → stutter and freezes.

  • Enough RAM → smooth multitasking (many browser tabs + music + photo editor), fewer forced tab reloads, less in-game hitching.

  • RAM also buffers between a fast CPU and a slower SSD, keeping the CPU busy instead of waiting on storage.

DRAM → SDRAM → DDR: a quick history

  • DRAM stores data as electric charge and must be refreshed periodically (“Dynamic”).

  • SDRAM synchronized RAM that moves in step with the CPU clock → more stable and faster I/O.

  • DDR SDRAM transfers data on both clock edges (Double Data Rate). Today’s modules are DDR4/DDR5 SDRAM.

Generation gains: higher clocks, wider bandwidth, lower voltage, smarter power delivery.

DDR4 vs DDR5 (at a glance)

FeatureDDR4DDR5
Typical voltage~1.2 V~1.1 V (with on-DIMM PMIC)
Base speeds (JEDEC)~2133–3200 MT/s4800 MT/s and up (8000+ MT/s common on OC kits)
Bandwidth per DIMMLowerHigher (per-DIMM bandwidth scales more)
Power managementOn motherboardOn-module PMIC → steadier power delivery
Latency (general)Often lower at like-for-like clocksRaw clocks are higher; effective latency varies by kit
CompatibilityBoards with DDR4 slots onlyBoards with DDR5 slots only

⚠️ Slots differ. You cannot insert DDR5 into a DDR4 board (and vice versa). Always verify your board’s supported generation.

How Much RAM Do You Need?

  • Office / web / media: 8–16 GB

  • Gaming (1080p/1440p): 16 GB (heavy titles or lots of mods: 32 GB)

  • Photo/video editing / streaming / music production: 32 GB+

  • AI / heavy data / VMs: 32–64 GB (or more, as needed)

Balance is key: too little hurts performance; too much beyond your workload brings little real-world gain.

Speed, Timings, and Channels

  • Clock / Data Rate (MT/s): Higher = more bandwidth. Helps games that stream lots of assets, and creator/AI workloads.

  • Timings (e.g., CL36): Lower is better (less waiting per access). Compare at similar data rates.

  • Dual Channel: Install two matched DIMMs to double memory bandwidth vs single-channel.

  • XMP (Intel) / EXPO (AMD): One-click profiles that set rated speed/timings in BIOS/UEFI.

  • QVL (Qualified Vendor List): Check your motherboard’s RAM compatibility list for proven kits.

Brands and Modules

  • IC makers: Samsung, SK hynix, Micron (chips used across many brands).

  • Module brands: G.Skill, Corsair, Kingston/HyperX, Crucial, TeamGroup, etc.

  • General guidance:

    • Prioritize stability/compatibility → mainstream kits from reputable brands; check QVL.

    • For gaming/OC → consider higher-speed kits (e.g., G.Skill Trident Z, Corsair Dominator).

    • RGB is aesthetics only - nice for builds, irrelevant to performance.

Pre-Purchase Checklist

  1. Generation: Is your board DDR4 or DDR5? (They are not cross-compatible.)

  2. Capacity: Match to your workload (see guide above).

  3. Dual Channel: Prefer a 2-DIMM kit (e.g., 2×8 GB, 2×16 GB) rather than a single stick.

  4. Speed & Timings: Balance higher MT/s with reasonable CL. Enable XMP/EXPO after install.

  5. QVL Compatibility: Check your board maker’s list for the exact kit model.

  6. Heatsink Height: Ensure tall heatspreaders won’t collide with your CPU cooler.

  7. Brand/Warranty: Choose reputable brands with solid support and clear warranty terms.

Wrapping Up

RAM isn’t a storage box - it’s the workspace that lets your CPU fly.
Pick the right capacity and a sensible speed/timing for your workload, install in dual channel, and enable XMP/EXPO. You’ll feel the difference in responsiveness, load times, and overall workflow.

Next up: Storage (SSD/HDD) - speed, endurance, interfaces, and what actually matters when you’re buying.


You can view the original Korean blog post at the link below

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Location: 대한민국 서울특별시

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