Regular key-length is usually 1k, but highly secure environments, like banks, may be forced to use 4k.
Knowing that a key with 4k has about 64 times the need for processing power than a 1k key does, it makes sense that RSA4096 operations are approx. 64 times slower than RSA1024 operations.
In order to complete 30 RSA4096 transactions per second, the HSM needs to be able to do 1920 RSA1024 transactions per second. Thales HSMs always carry the speed index for the cards in the product name, and they mean RSA1024 operations per second.
So: At a speed index of 500 RSA1024 operations per second, you will get a maximum of 7,8 RSA4096 operations per second. At a speed index of 6000, you’ll get around 93,75 RSA4096 operations. Think about that before “sizing” your environment.