PC makers with plans to offer low-cost desktops using Intel Corp.'s Pentium III chip will need to go back to the drawing board lest their machines hang. An erratum that affects the Pentium III's SSE or Streaming SIMD multimedia instruction set is keeping Intel's new 810 chip set from working with the chip. The erratum, called MaskMovQ, is a Pentium III glitch. And while Intel has created a workaround for it, the 810 doesn't support it, making it incompatible with the Pentium III. Intel isn't supporting the workaround in the chip set because the 810 was not designed or validated to work with the Pentium III, said Intel spokesman Dan Fancisco. "If the two are put together, it could result in a system hang," he said. The 810, which ships this month, was designed as a low-cost chip set for Intel's Celeron processor. It integrates a 3D graphics engine and supports modem and audio functions in software to help reduce cost. While the Pentium III and the 810 do not work together, forthcoming Intel 800 series chip sets will work with the chip. Intel has not yet publicly acknowledged the chip sets' names, but according to sources they are the 820, code-named Camino, for high-end Pentium III-based machines; the 840, for Pentium III Xeon workstations and servers; and the 810E, also for Pentium III. Intel would not comment on the existence of the 810E, but sources said it is likely to be a lower-cost alternative to the 820. The long-awaited 820 chip set will offer a 133MHz system bus, 4X accelerated graphics port and support for Rambus Dynamic RAM. The 810E and 820 will be announced in September along with a 600MHz Pentium III chip, sources said. The 840 is also slated for a September launch, they said. In the meantime, those looking for desktop PCs based on the 810 will find them combined with chips such as the 466MHz Celeron or a 500MHz version of the chip that's due in August, sources said. Take me to the Pentium III Special.