Running out of storage while keeping your favorite PS2 games on NetherSX2? Choosing between CHD and ISO formats can decide how many games you store and how smoothly they run. This guide explains both formats in plain language so you can pick the one that works best for your device.
What Is the ISO Format?
An ISO is a 1:1 copy of a PlayStation 2 game disc. It contains all the original data exactly as it was on the DVD.
Key Points:
- Structure — Uncompressed, full-size game image.
- Average Size — Between 1GB and 4.5GB per game, depending on the disc’s original size.
- Data Integrity — Perfectly preserves all files, including unused or blank data sectors.
Advantages of ISO:
- Guaranteed compatibility with every version of NetherSX2.
- No additional processing is needed before playing.
- Works well for archival purposes.
Disadvantages of ISO:
- Larger file size means fewer games fit on your device.
- Takes longer to transfer between storage devices.
What Is the CHD Format?
CHD stands for Compressed Hunks of Data. Originally used for arcade game storage, it’s now widely adopted in console emulation for its lossless compression capabilities.
Key Points:
- Structure — Compresses the game’s data blocks without removing any essential content.
- Average Size — 30%–50% smaller than the same game in ISO format.
- Data Integrity — Maintains full accuracy of original files, so gameplay is unaffected.
Advantages of CHD:
- Saves significant storage space.
- Faster loading from slower storage media in some cases.
- Ideal for building large game libraries on Android devices.
Disadvantages of CHD:
- Requires conversion before use if your game is in ISO format.
- Slightly higher CPU load when decompressing in real time.
Why Format Choice Matters in NetherSX2
The NetherSX2 emulator can run both ISO and CHD formats, but the choice affects:
- Storage Efficiency — CHD can store more games in the same space.
- Performance — ISO requires no decompression; CHD uses minimal extra processing.
- Organization — Smaller CHD files make backups easier.
On mid to high-end Android devices, CHD often delivers identical performance to ISO while saving gigabytes of storage.
File Size Comparison — CHD vs ISO
Here’s an example from typical PS2 titles:
| Game Title | ISO Size | CHD Size | Space Saved |
|---|---|---|---|
| Gran Turismo 4 | 4.2GB | 2.9GB | ~31% |
| Shadow of the Colossus | 3.6GB | 2.4GB | ~33% |
| Final Fantasy X | 4.0GB | 2.6GB | ~35% |
Observation: Converting 20 average PS2 games from ISO to CHD can save over 25GB of storage.
Performance Differences on Android Devices
Loading Speed
- ISO — Slightly faster on older devices without strong CPUs.
- CHD — Equal speed or faster on modern phones with efficient decompression.
In-Game Performance
Both formats deliver the same frame rates and visual quality on devices meeting NetherSX2’s recommended specs.
Battery Usage
Decompression in CHD uses a small amount of CPU power, but the impact on battery life is minimal on Snapdragon 845 or newer.
6. Compatibility with NetherSX2
- ISO — Works on all NetherSX2 builds without extra steps.
- CHD — Fully supported, but requires the latest stable or beta build to avoid rare bugs in older versions.
If you’re running a current release, both formats are equally compatible.
How to Convert ISO to CHD
If you want to save space, you can convert your ISO files to CHD format using CHDMAN (Command-line tool included with MAME).
Basic Steps:
- Download CHDMAN for your platform.
- Place the ISO file in the same folder as CHDMAN.
- Run the command:
chdman createcd -i game.iso -o game.chd- Wait for the conversion to complete.
After conversion, replace the old ISO with the new CHD in your game folder for NetherSX2 to detect.
When to Use ISO Instead of CHD
Choose ISO if:
- You are testing a game for the first time and want guaranteed compatibility.
- You plan to modify or patch the game, as some tools work better with ISO.
- You have abundant storage space and prefer direct, uncompressed reads.
When to Use CHD Instead of ISO
Choose CHD if:
- You want to fit the maximum number of games on limited storage.
- You maintain a large library and need easier backups.
- Your device has a modern CPU capable of real-time decompression without slowdowns.
Storage Planning for NetherSX2 Users
Example Scenario:
- 64GB phone with 20GB reserved for system and apps.
- Remaining 44GB for games.
With ISO:
- Average 3.8GB per game → ~11 games.
With CHD:
- Average 2.5GB per game → ~17 games.
Result: CHD adds roughly 6 extra playable titles without expanding storage.
Myths About CHD vs ISO
Myth 1: CHD reduces game quality.
- Fact: CHD uses lossless compression; graphics, audio, and gameplay remain identical.
Myth 2: CHD always loads slower.
- Fact: On modern Android CPUs, loading speed is usually equal or faster due to smaller file size.
Myth 3: CHD can cause crashes.
- Fact: Crashes are usually due to outdated emulator builds, not the format itself.
Backup and Archiving Considerations
For long-term storage:
- Keep an archive of either ISO or CHD on a PC or external drive.
- If you plan to share with other emulators, check their format support.
Recommended Approach for Most Users
- Convert your main library to CHD for space savings.
- Keep original ISOs archived in case you need them for patching or other emulators.
- Use NetherSX2’s game list rescan after adding new CHDs.
Final Thoughts
Choosing between CHD and ISO in NetherSX2 comes down to storage needs and device capability. ISO offers raw, unchanged data for maximum compatibility, while CHD provides the same experience in a smaller package. For most Android users, CHD is the smart choice, keeping libraries compact without sacrificing performance or quality.