Useful question. I am obviously content at the moment with 26C or 5C above room, which is now 21C of 70F. The lower the better. But my ownly source of measurement at the moment is my motherboard temp -- no thermal sensor on the case panel. It may be closer to 23.
Someone is either having a cold day or has a superb cooling solution at 23C.
The lower the better! At 70F, my idle CPU is in the 80 to 82F range, and at extreme load the CPU temp never goes above 104F -- at the over-clock setting below and the above room value:
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'95 Gateway2000 full-tower mod
P4P800-standard ASUS mobo
P4-C 3.0@3.6
OCZ EL Gold DDR500 -- 2.5, 4, 4, 6 @ DDR480
ASUS V9980 FX5950 Ultra 256
Creative SB Audigy 2 ZS
dual Hitachi 7K250 SATA150 in RAID0
Sony DRU700A burner
ALLIED AL-B500E PSU
ThermalRight XP120 hs with YS-Tech 120x38mm fan and Ultra screen filter