In fact it is A80486DX2-50 for upgrade A80486SX 16-25 and A80486DX 25. CPU has 487SX pinout (169pins) and is intended for OverDrive socket. One extra pin assigned to disable the Intel i80486SX CPU. Original CPU can be removed.
Manufacturer: Intel Type: Microprocessor Introduced: June 1993 Name (codename): 486DX2 OverDrive Processor (P23T) Code (Copyright): DX2ODP50 BOXed (Intel 1989 1992) Specification number: SZ902 Core speed: 32MHz(16MHz BUS), 40MHz(20MHz BUS) or 50MHz(25MHz BUS) BUS: 16MHz – 25MHz, 32-bit Transistors (Die size): 1 200 000 (81mm square) Technology: 0.8-micron L1/L2 cache: 8kB / to 512kB (external, BUS speed) Can address: 4 GB of physical and 64 TB of virtual memory FPU: Integrated Whetstone FPU: ?MFLOPS Drystone ALU: ?MIPS V core (typical/max.): 5V – 6.5V Power dissipation (typical/max.): 3.75W – 4.75W (at 50MHz) Operating temperature (min./max.): 0 – 95°C Package (Socket): Ceramic PGA-169pin (Socket 2,3) Dimensions: 44.5 x 44.5 x 13mm