krupski:
For AVR devices that have the "low power / full swing" crystal drive option (low fuse, bit 0 (CKSEL0)) the low fuse, bit 0 should be programmed (that is LFUSE should be 0xF7 instead of 0xFF) - this sets the crystal oscillator to full swing which makes the board a lot more stable (runs fine at lower voltages, doesn't flake out if you hold the board and accidentally touch near the crystal, etc..).Why the Arduino default is 0xFF (low power oscillator) is beyond me. The Icc difference is only a milliamp or so......
Thankyou for your reply, Is it simple to said, using LFuse: F7 better than FF, but both of them are work fine for external 8MHz.