The CPU is an important choice in any PVR. It's not difficult to find a CPU that is up to the task of encoding, decoding and tons of I/O, but the way in which that power is obtained can make all the difference in your budget, power and heat dissipation requirements. In the master plan, I stated that I wanted a dual-core or SMT (Symmetric Multi-Threaded) chip to allow for decoding and streaming display activities to be performed in parallel. The new AMD Dual-Core chips are great performers and fit this spec well, but at $371
, the cost of this chip would blow more than 1/3 of the budget allocated. Nice thought, but maybe I'll get an upgrade in a few years when the cost is lower.
So now that we have decided on an AMD 64, there are a few obvious options that make the selection process easier. 64 bit extensions are an in-expensive way to boost performance a bit and prepare for any software considerations for these extensions in the future. The 64 bit extensions don't add much to the cost of the CPU either. The next obvious choice is Socket 939. Most future desktop level AMD chips will be based on this socket interface for the foreseeable future. The 939 replaces 754 socket interface.
Now, I head over to the AMD Athlon Chip Reference
guide to pick up the part numbers for the frequencies and power consumption I'm looking for. I have not purchased CPU's for some time (6-7) years, and I don't want to do it again any time soon, so I start looking at the fastest clockspeed and smallest fab tech I can find. Hmmm... a 90nm San Diego chip includes a 1Ghz frontside bus, that'll be great for massive disk, memory and TV card I/O. $1100
! Maybe not. Ok, that was a harsh introduction into the world of CPUs in 2005. Ok, I'm willing to sacrifice the blazingly fast FSB for a discount, but I want a high clock-rate to enable the PVR to keep up with all the encoding and decoding. Here is a San Deigo chip with twice the L1 cache as the Venice chips and the full 2.4Ghz available in the standard Athlon 64. $500
! Still half of my total budget and way too much. Let's try to cut that in 1/2 again. A quick comparison
of the San Diego and Venice chips reveal that there is not much real-world advantage to the extra on-chip cache. Venice is it. Let's try the 3500+... $218
AMD Athlon 64 3500+ 2.2GHz Venice Core, 512KB L2 Cache, 90nm ...
$218.49 - xPCgear.com: 4.1 / 5
AMD Athlon 64 3500+ 2.2GHz Venice Core, 512KB L2 Cache, 90nm, Socket 939 CPU Processor, ADA3500BPBOX/ ADA3500BWBOX (Retail with Fan and Heatsink, 3-Year AMD .