Intel Pentium Overdrive 83
The Pentium Overdrive is a chip to turn a socket 3-based system (486) into a Pentium. Of course it isn't really possible to get Pentium-like performance and the Pentium Overdrive didn't. It featured twice as much L1 cache (32KB over 16KB) compared to the 'real' Pentium but had to work on the slower 486 33MHz-bus with 32-bit memory access. At last the Pentium Overdrive wasn't supported on every socket 3 motherboard so upgrading to this, expensive, chip wasn't always possible at all.

