Overclocking the Warp Engine

The Warp Engine is a 68040 accelerator which was made in two versions - for the A4000 and the A3000. The A4000 version has four SIMM sockets for a total of 128MB of RAM. The A3000 version has two sockets for a total of 64MB of RAM. It is also available in three speeds - 28MHz, 33MHz and 40MHz. The 28MHz version is often supplied without a 68040 chip so that the user can use his 68040 from his old A3640 board. It is this version which I have overclocked.

I have overclocked my Warp Engine with two different CPUs - both were 25MHz 68040s originally from old Commodore A3640 boards. One 68040 has worked reliably at 40MHz on the Warp Engine for 3 years, the other had FPU problems when running at 40MHz, however this chip worked fine at 33MHz. Due to the fact that the Warp Engine is designed to operate at up to 40 MHZ, the only issue that 28MHz and 33MHz users need consider is how their CPU reacts to overclocking.

The Warp Engine uses a PLL (Phase Locked Loop) to generate the Processor Clock (Pclock) signal for the 68040. This is twice the frequency of the oscillator. Increasing the frequency too much past its maximum rating of 40 MHz can result in incorrect operation of the PLL, and a poor Pclock signal. Several users have tried overclocking their 40MHz Warp Engines and have found it is usually good up to about 44-45 MHz. One user did obtain erratic operation past 48MHz with several chips on the Warp Drive starting to overheat. This means that the suggested maximum speed of a Warp Engine should be about 44MHz.

A separate 50MHz oscillator module drives a divider to generate 25MHz for the SCSI controller and motherboard timing. This means that overclocking the processor will not have an adverse effect on the SCSI controller. As an experiment I tried overclocking this by replacing the 50MHz oscillator with a 66MHz version, giving a clock of 33MHz. My system worked reliably this way for 3 years with a modest improvement of several MB/sec for Zorro III data transfer speed. Another user tried this as well, however he did not get correct SCSI operation and had to change back to a 50MHz oscillator.

The Warp Engine is easy to overclock. The two oscillators are located in the corner opposite the 68040. The oscillator controlling the CPU is already socketed, so it is easy to identify and change it. The SCSI crystal is a 50MHz version which is soldered in place. Don't forget to note the correct orientation of the oscillator before changing it. Putting an oscillator in the wrong way will destroy it. Oscillators used are standard 8-pin DIL form factor (the small square type).

It is possible to convert the Warp Engine to operate with a 68060, although I haven't tried it. This is achieved by the use of a special adaptor which is placed in the 68040 socket and then plugging the 68060 into the adaptor.RS Components sells such an adaptor, however it costs about $800 in Australia, without the 060! Might be cheaper to get a proper 68060 card! I guess the adaptor is intended for Mac users who are used to expensive hardware. If anyone can find a cheap source for these, let me know. I'll post the details here.

Clock division ratios:

68040 CLOCK=oscillator clock x 1 and oscillator clock x 2

SCSI AND MOTHERBOARD CLOCK=oscillator clock / 2

Points to watch:

* Pay attention to correct crystal orientation. Getting it wrong will destroy the crystal.

* Keep the CPU cool. The 68040 will generate a lot of heat. Use a heatsink & fan, especially in a desktop A4000 or A3000.

* Make sure the 200 pin CPU connector and SIMM sockets are clean and making good contact. I once had a fault caused by a bad contact in a SIMM.

* Absolute maximum recommended speed for the Warp Engine is 44-45 MHz.

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Introduced 30th July 1998. Updated 30th July 1998. Version 1.0