I AM looking for a new PC and want to know the difference between a 486DX4 computer running at 100 megahertz and a Pentium running at 60 MHz. Is the 486 a faster processor because it runs at 100 MHz, and if so why should I spend more money on a Pentium machine? If not, what is the advantage of the Pentium? ROGER CHEUNG Stanley To answer your question very simply, the Pentium 60 will leave the 486DX/4 standing still. According to tests, the Pentium is about one and a half times faster than the 486DX4/100, or about twice as fast as Intel's 486DX2 model and five times as fast as its 486SX. A lot of people get confused by trying to compare megahertz, which is a measurement of the frequency at which the microprocessor operates. While megahertz is one component of overall processor performance, it is not, by itself, a good measurement of processor speed. So says Intel itself. 'Megahertz can be compared to revolutions per minute (rpm) in a car's engine,' the company adds. 'When comparing engines, horsepower is a better indicator of performance than rpm. This is because a small engine might operate at high rpm but have much less power and performance than a bigger engine. In the same way, faster frequencies do not always translate into faster microprocessors.' DOES a triple-speed CD-ROM drive have any huge advantage over a double-speed drive? I want to buy one but am not sure if I should buy one of the cheaper double-speed drives freely available today or wait till the prices of triple-and quadruple-speed drives drop - as they are bound to - and buy one of them. BEN MACDONALD Tsim Sha Tsui Some people I know will definitely criticise me for saying this, but unless you plan to use your CD-ROM drive for high-end work, a double-speed drive is all you need for now. Double speed drives are the ones most commonly sold with most computers in Hong Kong today and as such are a current standard. This means all of todays's commonly available software products will be compatible with double-speed drives. On the other hand, triple-and especially quadruple-speed drives are thought of as being state of the art. This means you pay a lot of money for them. If you are a high-end user and every second of access time counts for you, a higher-speed drive will be of use to you. If not, just get a double-speed drive for now and upgrade to a faster one when it becomes obsolete. I NEED to create an index for an instruction book I am writing. Is there any software out there that will automatically create an index along with page numbers. My word processor will create a table of contents, but I have to do most of the work. NAME AND ADDRESS SUPPLIED WordPerfect 6.0 for Windows provides you with a fully automatic index generating feature. FrameMaker version four from Frame Technology in the US (telephone  433-3311) also provides a similar feature. The problem is that these are fully featured packages and cost several thousand dollars. Rather a lot to spend for just one feature, especially if you already use another word processor and page layout application. If you use Quark Xpress, you can get extensions that perform indexing functions. Your best bet would be to get onto the CompuServe on-line information service and post your question on its Desktop Publishing Forum. There may well be shareware applications on CompuServe you could use. As another alternative, consider a program called Indexicon. This is one I read about recently on the Knight-Ridder wire service. It is supposed to search your document, select what it sees as important words and even complete phrases in your text. It is supposed to be able to distinguish semantic and syntactic differences, as well. Take a word such as 'lead', for example. From the context of how the word is used, the program knows if you are referring leading a group of followers or instead discussing the metal. It then creates a back-of-the-book index. For more information, telephone Iconovex, the program's vendor, on (612) 943-0292 Send your questions to Tech Talk, Technology Post, G. P. O. Box 47, Hong Kong, or fax them to 2811-1278.