How does mysql order rows with the same value?

In my database I have some records where I am sorting by a column that contains identical values:

| col1 | timestamp              |
| row1 | 2011-07-01 00:00:00    |
| row2 | 2011-07-01 00:00:00    |
| row3 | 2011-07-01 00:00:00    |

SELECT ... ORDER BY timestamp

It looks like the result is in random order. Is the random order consistent? I have these data in two mysql servers can I expect the same result？