TECH TIPS FROM FRED…

By Fred Henning 7.98

Speed…Today I would like to talk about what makes a PC fast and just what fast should mean. First; I’ll discuss the 400 Mega Hertz (MHZ) Pentium PC ads on TV. Other than the "male thing'" about "he who has more power or biggest toys) wins" logic, I can't see why anyone needs a 400MHZ PC for home use. You can't type any faster, you can't play solitaire any faster and you certainly can't make the Internet any faster just because you have a 400MHZ PC. I even have a hard time believing that those that play 3D CD-ROM games can tell the difference between a 200MHZ and 400MHZ machine.

The clock speed of the PC doesn't equate 1:1 to performance. A 400MHZ machine is NOT twice as fast as a 200MHZ machine - regardless of what a salesperson says! In a data intensive environment, where the speed of the machine can make a difference, doubling the speed improves the processing by perhaps 25 - 30%. The same types of performance improvements are associated with other items the salesperson wants you to buy. If the system comes with 16 Meg of RAM then won't 32 Meg be better? Tests show that for any given set of programs running on a Windows 95 PC there is a point of no return. 24 - 32 Meg has been the point for most sets of applications on a home or small business system. If you create or edit graphics using a high end application then both speed and memory are critical but not if you are using Power Point or Print Shop.

One of the biggest sources for performance improvement is very often misunderstood and over looked. There is something called L1 and L2 Cache. This is memory that is physically on the same piece of silicon as the CPU or is on the same sub-system as the CPU. This memory stores the next instructions that will be processed and allows some very fancy programming to look ahead at the coming instructions to see if the CPU can do one or more other instructions while waiting for another to finish. The same is true about bringing data that will probably be used next in the processing out of RAM and into the very fast Cache memory. Even though this is where performance improvement is best, Intel has chosen to supply Pentium chips without it just so retailers like Best Buy, Circuit City, etc. can advertise low cost machines and say they have Intel Pentiums.

I sometimes joke about the fact that we are using Intel Pentium 200 based machines, running UNIX, here in the Data Center. Aren't they just PCs? Our machines are made by Data General and are designed to get the best possible performance. The data path to the hard drive on your PC can transfer data at 10 Megabits per second. Our systems transfer data at 40 or 80 Megabits per second. The information between the various inputs and outputs on your PC may run on a 32 bit PCI BUS at a rate up to 130 megabits/sec. The DG systems have a 64 bit wide bus that moves the data around at 533 Megabits/second. The L2 cache is at least 512KB not 16KB or 64KB that you find on a retail machine. The home PC may have 32 Meg of RAM and we have 512 Meg, but we have 250 users at a time not just 1. I guess they are not just expensive PCs!