The 486: An FPU And Multipliers Too
The 486 is emblematic of a certain generation who were first discovering computers. In fact, the very famous 486 DX2/66 was long considered the minimum configuration for gamers. This processor, released in 1989, ushered in several interesting new features, like an on-chip FPU, data cache, and the first clock multiplier. The former consisted of an x87 coprocessor built into the 486 DX (not SX) series. An 8 KB Level 1 cache was built into the processor (write-through type, then write-back with slightly better performance). There was also the possibility of a Level 2 cache on the motherboard (at the bus frequency).
The second generation of 486s had a CPU multiplier, since the processor operated faster than the FSB, with DX2 (2x multiplier) and DX4 (3x multiplier) versions. Another anecdote: the “487SX” sold as an FPU for the 486SX was actually a full 486DX that disabled and took the place of the first processor.
|Code name||P4, P24, P24C|
|Data bus||32 bits|
|Address bus||32 bits|
|Maximum memory||4096 MB|
|L1 cache||8 KB|
|L2 cache||Motherboard (FSB frequency)|
|Clock frequency||16-100 MHz|
|Fabrication process||1,000–800 nm|
|Number of transistors||1,185,000|
|Voltage||5 V–3.3 V|
|Die surface area||81 - 67 mm²|
The DX4 had a 16 KB cache and a few more transistors: 1.6 million. This processor, using a 600 nm process and measuring 76 mm², consumed less power than the original 486 (at a voltage of 3.3 V).