Sources close to Advanced Micro Device (AMD) said that the firm's up-and-coming Spitfire range of microprocessors are forcing the firm's hand on its integrated cache Thunderbird chips. Thunderbirds are versions of the Athlon microprocessor with large level two caches, which come in Slot A configurations. Caches for the T'birds are likely greater than for the Spitfires. The Spitfire chips, which will use a plug in packaging AMD calls Socket A, are unlikely to get themselves a new spiffy name, such as the K7 did when it became the Athlon, but instead are likely to be branded either Athlon Performance or Athlon Enhanced Cache. However, the same sources tell The Register that the line is performing so well in its sampling that they are actually, in many cases, outperforming their elder brothers, the existing Athlon range of microprocessors. Spitfires also have on-die cache, and although AMD is keeping details close to its corporate chest, the amount of cache will be less than Thunderbirds. The speed that Spitfires are performing means their release, slated for mid- to late-May, will be delayed for a while, probably just a few days, the same sources said. AMD is now likely to release its Thunderbirds -- Athlons with larger integrated caches -- at the same time. That will help avoid the possible embarrassment of junior doing better than senior. Problems like this Chipzilla should have. AMD's share price rose to $78 1/8 as Wall Street opened. It delivers its quarterly financial results on the 12th of April next. ®