We examine how PCs have evolved since PC Authority began, and put a vintage machine through its paces by feeding it the application tasks of today.
Looking back over the past decade, you can see the rough-and-ready interpretation of processor speeds as indicated by FLOPS. This is only a basic indication, based on maximum theoretical floating-point operations per second. It’s a purely theoretical number based on the notion that the floating-point units can complete a certain number of operations per clock cycle. For early processor designs, this was simply one operation per clock, hence a 333MHz Pentium II could, in theory, manage 333MFLOPS (a MFLOPS is one million FLOPS).
Real performance benchmarks, on the other hand, are based on hundreds of other factors. You’ll notice that the theoretical MFLOPS performance didn’t alter between our average Labs-test PCs in a two month period, because both had 3GHz Pentium 4 processors. The maximum theoretical floating-point performance of any Pentium 4 is simply the maximum number of floating-point operations per clock, multiplied by its clock frequency; the 128-bit SSE registers in a Pentium 4 allow four floating-point operations in a single clock cycle in the ideal case, making for a maximum FLOPS rating of 12,000MFLOPS (or 12GFLOPS). But in fact the Pentium 4 variant in our later tests was a superior part for real-world applications, having more cache memory and Intel’s HyperThreading system, which presented the system with a second virtual processor constructed from idle resources. In practice, of course, real-world performance is about the complete PC, which is what PC Authority’s application-based benchmarks have always been about.
Application benchmarks are the only way to really measure true performance, especially today. Most architectural enhancements in processors – such as branch prediction, out-of-order execution and speculative instruction fetch – rely on the typical non-linear nature of applications. Feeding them synthetic tasks that simply repeat the same tight loop over and over again doesn’t simulate that.
Second, of course, the processor is only one of half a dozen or so key components that affect performance. The speed of ancillary components is more important in the real world for many apps – hard disk speed chief among them – and the bandwidth of internal buses and interconnects is a major bottleneck when it comes to shuffling data from processor to memory and graphics card. With that in mind, how does a machine from several years ago fare against one of today?
In context
Back in 1994, the PCI bus was the height of new technology. Running at 33MHz with a 32-bit bus width to the ageing ISA bus’ lowly 8MHz at 16 bits, it could push around 125MB/s between a graphics card and main memory. The (now obsolete) AGP port wouldn’t be invented for another three years, and the idea of a serial interface for anything that needed seriously fast transfer rates was pure fantasy; parallel buses were clearly superior, since you could push a couple of bytes per clock down the pipe as opposed to just one measly bit. 1994 hard disks were connected with an early version of the IDE (integrated drive electronics) interface. With a bandwidth of 33MB/s, it was more than sufficient, since only the fastest hard disks could approach10MB/sec transfer rates. Incidentally, hard disks were all formatted with the FAT16 filing system, meaning you couldn’t have a single partition larger than 2GB. This wasn’t a terrible burden, as the largest hard disks were only around 540MB anyway.
These days, the serial-transfer paradigm has sensibly taken over from the old parallel way of doing things, and bandwidth is frighteningly high. Issues of cross-talk and clock-skew meant that parallel interfaces had hit the buffers and extremely high-speed serial interfaces are now the way forward. Hence, we have SATA and PCI Express, both based on the same fundamental high-speed serial transfer technology. Where the PCI bus of 1994 could transfer 33MB/s, the PCI Express interface of today can push 8GB of data from north bridge to graphics card every second.
And where the PATA-based IDE hard disk interface of 1994 topped out at 33MB/s, SATA can now shove 300MB/s down the pipe. This is just as well, since a single high-end hard disk such as Seagate’s 15K Cheetah can now achieve almost 100MB/s, and formerly stupendously expensive RAID multidisk capabilities are routinely built into motherboards costing $80. Just hook up a few consumer-level drives costing $150 or so and you’ve got 100MB/s, no problem.