the nintendo 64's central processing unit (cpu) is the nec vr4300, a licensed variant of the 64-bit mips technologies r4300i, itself a cost-reduced derivative of the mips r4200. built by nec on a 350 nm process, the vr4300 is a risc 5-stage scalar in-order execution processor, internal 24 kb direct-mapped l1 cache (16 kb for instructions, 8 kb for data). although a floating-point unit exists as a logical coprocessor, there is no dedicated physical fpu datapath on the vr4300; instead, the integer pipeline is shared for this purpose, meaning that floating-point instructions will stall the pipeline. the 4.6 million transistor cpu is cooled passively by an aluminum heatspreader that makes contact with a steel heat sink above.