Introduction — continued

Here are some nudies of the C3 to ogle.


It says "fan required," but one isn't, really


The C3's Socket 370-style pinout


Passive cooling: shhhh

A new take on the MHz myth
Unlike AMD and Apple, who would like to remind you that a processor's IPC (instructions per clock) is more important than its clock speed, VIA is happy to play the MHz game. VIA's C3 processor data sheet lays it out in black and white:

Improving clock frequency has higher leverage than improving CPI. The result of advanced computer design approaches over the last few years has been that the improvements in cycles-per-instruction (CPI) often impact MHz improvements, and certainly impact die size. Our belief is that the best way to improve total performance and keep a small low-power die is to improve MHz.

Thus, the VIA C3 Ezra processor family architecture provides improved performance by optimizing MHz via a 12-stage pipeline while maintaining a good CPI. Complex CPI-driven features such as out-of-order instruction execution are not implemented because they (1) impact MHz, (2) require a lot of die area and power, and (3) have little impact on real performance sinceÂ… (the next point)

Memory performance is the limiting CPI performance factor. In modern PCs, the processor bus is slow compared to the internal clock frequency. Thus, off-chip memory-accesses dominate processor CPI as opposed to internal instruction execution performance.

The VIA C3 Ezra processor family addresses this phenomenon by providing many specific features designed to reduce bus activity: large primary caches, large TLBs, aggressive prefetching, an efficient level-2 cache (new to the VIA C3 Ezra processor), and so forth.

The fact that consumers are more easily placated by high MHz values than more complex explanations of IPC helps, too.

VIA's stance is understandable. They're building simple, cheap processors with low power and cooling requirements. For their target markets, they've determined that those factors are more important than performance, and they might be right. Intel was in a slightly similar situation with the introduction of its Pentium 4 processor, whose design was optimized to allow for astronomical clock speeds. Only at around 2GHz did the Pentium 4's performance really get compelling, but the relatively high clock speeds forced AMD to play name games. Since the C3 is only available up to 933MHz, however, VIA hasn't been able to leverage significantly higher clock speeds than the competition.