Always verify the MD5 hash of your firmware files to ensure they aren't corrupted before installing.
Since you are on 4.89, you cannot simply install a 4.88 update file over it; the PS3 will block it as an "older version." You must exploit the system memory (Flash) to allow the installation of older or custom software.
The PlayStation 3 modding scene remains active, but Sony’s 4.89 firmware update introduced specific hurdles for those looking to revert to older versions or install Custom Firmware (CFW). If you are looking to downgrade from 4.89 to 4.88, the process is not as simple as clicking "undo." It requires specific hardware compatibility and software exploits. Can You Downgrade Any PS3? No. Before starting, you must identify your console type. Most are downgradeable. how to downgrade ps3 firmware 4.89 to 4.88
These are generally compatible with downgrading and CFW.
The PS3 cannot read USB drives formatted to NTFS or exFAT. Always verify the MD5 hash of your firmware
Follow the prompts to patch your NOR/NAND Flash memory. This "tricks" the console into accepting firmware that isn't digitally signed by Sony for that specific version. Step 3: Installing 4.88 Custom Firmware (CFW)
Doing this removes your ability to run homebrew apps. ⚠️ Essential Safety Tips If you are looking to downgrade from 4
If your goal was to get back to a "clean" 4.88 Official Firmware (OFW): Install the 4.88 CFW first using the steps above. Once on CFW, the system restrictions are gone.
Place the PS3UPDAT.PUP file on a FAT32 formatted USB drive in the folder path: USB -> PS3 -> UPDATE .