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***Edit***Just remembered (don't know how I forgot) I had a Hiper Type R 580w that blew up on me and took a 2 week old DFI motherboard with it. That's the one time reviews and feedback has let me down.
Anything AMD.
5 - 5870 Crossfire. Superb when CF was supported in a game mind, but support was patchy.
4 - Gigabyte Z97X-UD3H-BK motherboard. Wouldn't run ram over 1600 Mhz, constant BSODs, accessing the BIOS was a lottery. Had two of these and both were the same on every BIOS. Replaced with current board = all fine.
3 - I too had a Cyrix MII 300. The floating point unit was so poor that it could either power a USB modem, or play a game - the modem would disconnect the moment the CPU had any other load on it. "Upgraded" to an ISA modem so I could play HLDM and TFC
2 - Athlon XP 4400+. Not that bad, just utterly destroyed a few months later by the much cheaper members of Core 2 Duo family.
1 - The winner by a country mile. nForce 680i motherboard. Ran like a furnace, despite being utterly unable to overclock the CPU at all. Physically burned myself touching the northbridge heatsink to check it was making contact, and that was after the machine was turned off.
I've had my share of badly timed GPU purchases, but am thankful that I've avoided any truly bad cards. I appreciate my 980s but would have snapped up the Ti instead had it been available at the time.