Our application was using MySql version 4.0.24 for a long time. We are trying to migrate it to version 5.6.27. 
But, on testing the performance on 5.6.27, even the simple selects and updates are 30-40% slower when we are doing load testing. The CPU and IO speeds are much better than the older server. The storage engine of the tables is MyIsam in both versions. There's only one connection to the database. We tried the following options:

1. Changing storage engine to InnoDb - this reduce the performance drastically (70% slower)
2. Changing the innodb log size and buffer size - didn't help much
3. Increasing key buffer size with MyIsam storage engine for tables. - It made no difference

We tried modifying other parameters like query cache, tmp\_table\_size, heap\_table\_size. But, none of them made any difference.

Can you please let me know if there's any other option that we can try?

Here's a copy of my.cnf:

```
lower-case-table-names=1
myisam-recover=FORCE
key_buffer_size=2000M

```