does anybody know what the main difference between the Pix 525 and 535 is? Cisco's documentation says that the 525 has a 600Mhz PIII CPU and the 535 a 1Ghz PIII CPU. The 400Mhz speed bump doesn't really explain the numbers below:
Pix 525(V+) Pix 535 (V+)
Max Throughput 330 Mbps 1.7 GBps
Max Throughput (AES-128) 135 Mbps 495 Mbps
The Pix 535 is over 5 times faster with clear text and over 3 times faster with AES-128. The 525 has a single 32-bit, 33-MHz PCI slot but that can't be the limiting factor.
I don't know that there is a good way to answer this question. The PIX 535 and the PIX 525 have a completely different hardware design which allows for the higher values. The 2 differences you point out in your original post are directly related to the bus speeds on each PIX. The PIX 525 has a single 32bit/33MHz PCI bus and 3 slots. The PIX 535 has 2 64bit/66MHz buses with 2 slots each as well as
a 5 slot 32bit/33MHz bus. The PIX 535 is able to take advantage of faster cards which allow more packet throughput as well as faster hardware acceleration for encrypted traffic.
Faster CPU and more memory also help some with the throughput but these factors are used mostly to allow for more concurrent connections.