I'd go with the AMD, as you can see from below it will be roughly twice as fast as the Pentium in Poser (your results will vary in other apps). Both the systems you mentioned are already pretty obsolete, though, if they were using new componets I'd try for something better. Biggest disadvantage of the AMD CPUs is the noisy cooling fans they require, incidently, they run a lot hotter than the Pentiums, the newer ones are better then the 1.4 Thunderbirds, though. The results, as reported by various members of the Renderosity forum: CPU, Speed, Amount of RAM, Operating System, time AMD 2000XP 1G RAM Win 2K 024 seconds AMD 1800 Mhz 1GB Ram Win XP 035 seconds AMD 1800+ Athlon 512 Mb RAM Win XP Home 037 seconds AMD XP 1800+, 1GB DDR RAM, WinXP 044 seconds AMD 1.4 Ghz Athlon, 768 Mb RAM, Win 2000K - 044 seconds. AMD 1.4 Ghz Athlon 768 Mb RAM, Win 98 048 seconds AMD 1.3 GHz 256meg RAM Win 98 048 seconds Pentium 4 1.7Ghz 384RDRAM WinME 063 seconds Pentium 4 1.9 Ghz 1Gb RAM Win XP 057 seconds Pentium 4 1.7 GHz, 256 MB RAM, 067 seconds AMD XP 1800+ 1 GB DDR Windows 2000 Pro 068 seconds Pentium 3 1 Ghz 256Mb Ram, Win 98, 070 seconds. AMD 1700+ (Dual) 1Gb DDR Win XP Pro 073 seconds Pentium 3 850 Ghz 512 Mb RAM Win 98se 081 seconds Pentium 3 1GHz, 512 MB RAM, Windows XP Home 081 seconds. AMD 800 Mhz Athlon 768Mb Ram Win XP Pro 085 seconds Pentium 4 1.0 Ghz ? ? 090 seconds Pentium Celeron 600 Mhz 256 Mb RAM Win 2000 Pro 095 seconds Celeron 700mhz 128 MB RAM Win XP 105 seconds AMD 1.0 Ghz Athlon 768Mb RAM Win XP Pro 106 seconds AMD 1..0 Ghz Athelon 512 MB RAM Win98SE 107 seconds AMD 1Gb Athlon, 256Mb Ram, Win 98. 108 seconds Pentium 4 1.8 Ghz 512 Mb RAM 113 seconds AMD ? K6 146 Mb RAM 115 seconds Pentium 3 800MHz, 128MB RAM, Win98 134 seconds Pentium III 500Mhz, 384mb RAM, Win98SE 165 seconds Pentium 3- 525Mhz 256 Mb RAM, Win 98 178 seconds Mac G3-500 Mhz 768 Mb RAM ? 215 seconds Mac G3-400 Mhz 256 Mb RAM O.S. 9.0.4, 343 seconds Mac G4 500 Mhz 832 Mb RAM O,S. 9.2.2 476 seconds Mac 7500 / G4 300 Mhz 240M RAM ? 476 seconds iMac G3 233Mhz/ 160mb RAM OS9.2 615 seconds