It is not known how many Intel chips with doctored speed markings are presently in the SAR market. Counterfeiters stamp new speed markings on the processors higher than the original clock rating. They also sometimes 'overclock' the chips, or alter them to make them actually run faster, though this invalidates Intel's warranty and puts the chips at a higher risk of failure. They then are commonly sold in grey (unauthorised) markets to PC manufacturers and consumers throughout Asia. Some shops at Hong Kong's infamous computer malls sell processors obtained through the grey market. 'I always advise consumers to go to the [authorised] agents. Don't go to the side street to buy the famous brand-name products,' the head of the Customs and Excise Department's intellectual property bureau, Calvin Leung Ho, said. Top-name vendors reportedly turn to the grey market when they need chips on short notice. One industry analyst said such instances would be rare however, because top PC makers received supplies from chip-makers on a preferential basis. 'They have the infrastructure to do quality control,' the analyst said. An IBM China/Hong Kong spokesman said: 'We wouldn't buy from the grey market. We only source [Pentium chips] from Intel and if shipments come a bit short, we wait.' Buying from unauthorised sources would contravene the firm's contract with Intel, and warranties on the grey-market chips would be questionable, the spokesman said. The most commonly reported cases of Intel chip doctoring involve 266 MHz Pentium IIs dressed up as 300 MHz models. So how can you tell if the speed of your Pentium II chip is genuine? A close inspection of the chip's shiny black plastic casing may reveal slightly washed-out letters or matt surface areas that reflect light unevenly due to the acid used to remove the original speed marking. The original lettering also may be visible under ultraviolet light. If the chip was put in a fake case, the 'Pentium II' lettering may appear off-centre and/or smaller than on an authentic chip. German computer magazine c't has posted an article on its Web site that features photos of doctored Pentium II chips, compared with the genuine product (www. heise.de/ct/english/98/07/018/). The magazine also has a downloadable test program ( www.heise.de/ct/p2info ) it claims can determine whether a 300 MHz Pentium II chip is genuine. If you suspect your chip has been tampered with, return it - otherwise, your warranty may be invalid if the chip fails. Intel did not reply to Technology Post queries.