Ok. You have three options.

1. 128ms = write 32 bytes one at a time
2. 1ms = compare 32 bytes and find unchanged.
3. 5ms = compare 32 bytes and write page

The AT89S8253 has 2048 byte of EEPROM. So the 64 pages would be:

1. 8.2 seconds
2. 64 ms
3. 320ms

In practice, you would be comparing some value between 64 and 320ms with the 8192ms.

Yes. There is never anything for free. You can hardly write the whole 2k when you detect a power loss. But a smaller # of bytes could be managed.

David.