What are the functions of these three DIP8 IC?

There is only one 8-pin DIP, EN25T80, which is made by EON Company, with 8 megabytes (1 megabyte) flash memory and working voltage of 2.7~3.6V, 100MHz clock for data storage and encryption.

Another big one is very common, Hynix's DRAM (Dynamic Random Access Memory), which is used for buffering.

Search the midline HY57… on the Internet … and there will be a PDF data manual.