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 |
| Date released | 1989 |
| Architecture | 32 bits |
| 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 |
| FSB | 16-50 MHz |
| FPU | On chip |
| SIMD | No |
| Fabrication process | 1,000–800 nm |
| Number of transistors | 1,185,000 |
| Power consumption | N/A |
| Voltage | 5 V–3.3 V |
| Die surface area | 81 - 67 mm² |
| Connector | 168 pins |
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).
