Installing Intel DX/4 and Pentium Overdrive Processors in Apricot Products

THIS BULLETIN SUPERSEDES IPB 4148 DATED 15 JUNE 1995

INTRODUCTION

The first 486 produced by Intel was the 486DX-25. It was a PGA (Pin Grid Array) device which plugged into a socket on the motherboard, a 33MHz PGA variant soon followed.

A low cost device, the 486SX was introduced. Available in two packages, PGA & QFP (Quad Flat Pack). The QFP variant was a surface mount device which was soldered to the motherboard.

The other main difference between the 486SX and 486DX processors was that the 486SX processor did not have a floating point (487) unit in the processor.

The next 486 to be introduced was the 486DX/2, this was a PGA device that internally ran at twice the external clock speed. The two main variants are 486DX/2-50 (25MHz external, 50MHz internal) and 486DX/2-66 (33MHz external, 66MHz internal).

DX/4 processors run at THREE times the external clock frequency. The two variants are the 486DX/4-75 (25MHz external, 75MHz internal) and the 486DX/4-100 (33MHz external, 100MHz internal).

Overdrive Processors are supplied with installation instructions, tools and diagnostic software.

There are two types of Overdrive ODP and ODPR. ODP devices are designed for machines that have a processor socket and an Overdrive/487 socket, upon installation in the Overdrive/487 socket the Overdrive disables the existing processor. ODPR devices replace (hence the R in ODPR) the existing processor.

NOTE: At the time of writing Apricot Computers do not sell Intel Overdrive upgrades. These must be purchased from an authorised Intel Distributor.

PROCESSOR SOCKETS

There are 5 main types of Processor sockets used in Intel based 486 and Pentium machines, it is important that Overdrive processors are installed in the correct sockets, otherwise damage may occur to either the board or the processor.

SOCKET TYPES
Socket 1 - 169 pin socket which operates at 5V. It takes DX/2 & DX/4 Overdrives but not the Pentium Overdrive.
Socket 2 - 237 pin socket operating at 5V. Will take DX/2, DX/4 & Pentium Overdrives.
Socket 3 - 237 Pin socket operating at 5V. Will take DX/2, DX/4 & Pentium Overdrives.
Socket 4 - 5V socket for Pentium 60 and 66 Processors.
Socket 5 - 3.3V socket for Pentium 75, 90 & 100 Processors.

Apricot 486 based desktop products use the following socket types;
Socket 2 - XEN-LS II, XEN-PC (SA/SD/SF), XEN-PC, XEN-PCm, XEN-PCls (SH/SJ)
Socket 3 - XEN-PC, XEN-PCm, XEN-PCls (RC/RD), LS-Pro (BP)

Sockets 1 and 2 are LIF (Low Insertion Force) sockets which require a tool to remove the processor whilst sockets 3, 4 and 5 are ZIF (Zero Insertion Force) sockets which allow the insertion and removal of the processor via a lever.

486 BASED INTEL OVERDRIVE PROCESSORS

The information listed below gives an indication as to which of Apricot's recent and current 486 desktop products are able to accommodate DX/4 Overdrive Processors.

PENTIUM OVERDRIVES

Intel have now extended the Overdrive family with Pentium Overdrives, these processors are designed to give Pentium type performance to 486 based machines.

Currently there are two variants of Pentium Overdrive available the PODP5V63 and the PODP5V83. PODP stands for Pentium OverDrive Processor, 5V means that the upgrade is for 5Volt processor sockets 63 and 83 is the internal clock speed. The Pentium Overdrive processors internally multiply the external clock frequency by 2.5. Therefore the 63MHz Overdrive is for 25MHz systems and the 83MHz OverDrive is for 33MHz systems.

INSTALLATION

It is IMPORTANT that before commencing the Overdrive installation that the following actions are taken;

1. The following documents are read; Intel Overdrive Processor Installation Manual. Motherboard Jumper/Dip switch settings in either user guide or Apricot Insight.
2. Ensure that you are working in a static safe environment.

Installation is as follows;

1. Power down the machine.
2. Remove All external cables and the top cover from the machine.
3. Locate the processor socket & remove the processor according to the instructions in the Overdrive Processor Installation Manual.
4. Remove the Overdrive Processor from its packaging, check that there is no obvious external damage to the device, install the processor taking note of its orientation in the processor socket.
5. Put the original processor in the overdrive processor packaging.
6. Set the requisite jumpers and/or switches on the motherboard.
7. Refit the top cover and reconnect all external cables.
8. Power up the machine, in most cases the machine will automatically enter the setup/configuration program. All that is needed to be done in this situation is to save and exit.
9. Once the machine is up and running, it is important that the supplied Intel diagnostics are run so that the Overdrive processor can be tested.

If the machine does not boot, gives an error on boot or fails the Intel diagnostics then check the seating of the Overdrive processor and the jumper/switch settings.

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