Forinfinite analysis or long Time Control matches you should use the largest hash possible - typically about half of the total RAM memory of your computer. For example, on a system with 4 GB of memory you can use up to 2048 MB hash size, on a 12 GB RAM system you can use up to 8192 MB.

 

For shorter games, e.g. 3 to 5 minute games, it’s better to use 256 MB or 512 MB as this will provide the best performance. For 16 min games 1024 or 2048 MB hash size should be fine.

 

If you know the average move time T (in seconds) and the average node speed of your hardware S (in kN/s), you can compute the optimal hash size with the formula: (T x S / 100) MB.

 

For example if you use a Time Control of 10 minutes for 40 moves repeating, the average move time T = 15 seconds. On hardware that produces about 2,000 kN/s the optimal hash size would then be approximately (15 x 2,000 / 100) = 300 MB, in other words 256 MB or 512 MB would be the recommended values.