OverDrive processors

Phil Storrs PC Hardware book

The Intel OverDrive processor

During early 1993 some System Board manufacturers supplied Pentium upgradable System Boards. Intel announced the Pentium OverDrive processor in 1993 but it took nearly two years to deliver a Pentium OverDrive processor. Some System Boards have been advertised as having a Pentium OverDrive socket fitted but unfortunately some of these were released before Intel had finalised the Pin-out of it's Pentium OverDrive Processor.

To make the situation even more confusing Intel, in an attempt to make up for the delay in the release of the 64 bit +Pentium OverDrive chip, did release a 32 bit OverDrive processor called the 486 OverDrive. Intel produced a range of Overdrive chips in order to supply upgrade paths for most of the 486 hardware. 486 System Boards could have an 486 OverDrive chip fitted so long as they had :-

a special socket designed for an OverDrive chip
a 169-pin Intel 486SX or 487 socket
a 168-pin Intel 486DX socket used for your current CPU.

The type numbers of the common 486 OverDrive processors were:

Clock speed	Processor speed	Replaces a 486SX	Replaces 486DX
20	40	DX20DP50
25	50	DX20DP50	DX20DPR50
33	66	DX20DP66	DX20DPR66

The above chips feature: Internal maths co-processor
Internal clock speed is 2 times the external clock speed

Clock speed Processor speed Replaces a 486SX Replaces 486DX

20 60 DX40DP75

25 75 DX40DP75 DX40DPR75

33 100 DX40DP100 DX40DPR100

Clock speed	Processor speed	Replaces a 486SX	Replaces 486DX
20	60	DX40DP75
25	75	DX40DP75	DX40DPR75
33	100	DX40DP100	DX40DPR100

The above chips feature: Enhanced on-chip cache
Enhanced internal maths co-processor, Internal clock speed is 3 times the external clock speed

The Pentium OverDrive

The Pentium OverDrive chip requires a 237 or 238 pin PGA processor socket. When the Pentium OverDrive chip finally arrived it was discovered not all the System Boards manufactured with a Pentium OverDrive socket would actually work with the chip.

The Pentium OverDrive chips have a fan built into a heatsink on top of the chip but the 486 OverDrive chips only have the heatsink and do not require a fan on the processor chip.

The Pentium OverDrive chips

Clock speed	Processor speed	Replaces 486SX	Replaces 486DX
20	50	P0DP5V73
25	63	P0DP5V63	P0DP5V63
33	83	P0DP5V83	P0DP5V83
25	63	P0DP5V63	P0DP5V63
33	83	P0DP5V83	P0DP5V83

The features of these processors are, Superscalar Architecture, Enhanced On-Chip Cache
Faster Maths Coprocessor, Internal clock speed is 2.5 times the external clock speed.

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