Hi! I've doing some speed tests with 16F84 , XT and HS oscillators. I've found that the chip shows slight random failures @ 15Mhz (XT) which are not present @ 16Mhz (someone pointed this already on the list). For my test application (proprietary asynchronous protocol implementation using 3 pins and external interrupts, no peripheral use, such as EEPROM or WATCHDOG) the chip worked fine @ 18Mhz (light-processor-use app, so YMMV) and failed completely @ 20 and 24Mhz (XT always). But guess what...processor stabilizes @ 27Mhz (XT) and works for me! Of course this cannot be considered a though test (I will be doing something more serious when I get the ideal test code and try several other oscillators types) but I could increase the protocol speed of master/emitter devices (PIC is slave/receiver) to almost 7 times! Remember that PIC is not heavily used, but...so far so good! ------------------------------------ netQ http://virtuaweb.com/picprog "Home of amateur PIC programmers..." -----BEGIN PGP PUBLIC KEY BLOCK----- Version: 2.6.2 mQCNAzV38BkAAAEEALfWv9j3f+tZ+z2IW+2o9Ebx4bUGnHjHPqIe0a6yVKawaeV/ Y4I6L2/A0ddbVMG8+qJ0MvHNkr3DzYkpW+hTl9zAzXkKBdZ3GA5bbvot7entl/O2 YDtRWUV730koxBo5iFFUbJH5kbmkox+h3znj34zPnZNWzNaqOAwol3wABfBNAAUT tBxOZXRRIDxuZXRxdWFrZUBpbm5vY2VudC5jb20+ =0bVU -----END PGP PUBLIC KEY BLOCK-----