Apart from nice added features, improved stability and increased speed, there are two major factors that impact on your system setup:
1. 64 bit
2. Mercury Playback Engine
64 Bit only
This means a couple of things:
You need a 64 bit OS, you need 64 bit plug-ins and you can use much more memory than the 4 GB limitation that applied to 32 bit OS'es (with effective memory in the 2 - 3 GB range, depending on the Boot.ini switch).
In practice, to benefit from the move from 32 bit to 64 bit, the recommended memory needs to be around 8 or 12 GB, depending on your mobo and chipset and the number of DIMM slots available. With current prices (May 2010) it is not yet economical to opt for 4 GB sticks.
If you have a dual socket board with 12 or more DIMM slots, 24 GB is optimal.
Mercury Playback Engine
This is where it gets interesting.
In the past, up to and including CS4 4.2.1, performance was largely impacted by:
1. CPU
2. Memory
3. Disk setup
4. OS & Tuning
5. ...
and finally by the video card. It did not really matter what video card you had installed. There never was any discernable performance gain from expensive video cards.
The tables have turned.
With CS5, installing a CUDA enabled video card has a large impact on performance and lessens the burden on the CPU. The GPU does a lot of the work.
However, since the CPU gets a lot more breathing space, the CPU will no longer be the primary bottelneck, as was often the case in the past. And since all DIMM slots in the average machine will be occupied, it is a costly exercise to exchange the DIMM sticks with larger capacity ones. People who have only 3 slots in use on a X58 motherboard can directly benefit from adding three more sticks, but this does not happen very often.
So with the CPU running with a relatively low load and memory more or less a given, the only thing that may be a bottleneck to be improved upon is the disk setup. This can be seen easily by scrubbing fast through the time line with the popular AVCHD material. Due to the MPEG nature, while scrubbing one needs to look backwards and forwards to create the image under the CTI and that means a lot of disk activity. CPU is not a bottleneck, memory is not a bottleneck and the GPU is not the bottleneck, it is the disk setup.
Do not be fooled by the claims that SATA2 or SATA3 have enough bandwidth to support the data rate of AVCHD or other MPEG streams. Tests have shown that significant performance gains can be achieved by using a large number of disks, preferably in a raid. This is especially true when one has multiple tracks.
SSD's are not yet an economical alternative for conventional hard disks, with prices that are a factor 30 - 50 higher per gigabyte than conventional disks.
Conclusion
To fully benefit from the performance gains that CS5 allows, it may be that using a MPE supported card will lead to the disk setup being the new bottleneck. Be aware of that fact.
