Overclocking the GVP Combo 030 - Single oscillator version.

This popular A2000 accelerator card was made by GVP and contained a 33MHz surface mount 68030, a SCSI controller and a RAM expansion, using custom 64 pin "GVP SIMMs". It appears to be a cost reduced version of the other GVP Combo seen elsewhere on this site. It may also be of more recent design. This version has both the CPU & FPU running from the same clock. There is no facility to clock the FPU separately, nor is it easily possible to replace the CPU with a faster version.

This board has a standard 33MHz 14-pin oscillator module soldered in as can be seen in the top left of the above picture. There are no holes to allow use of the 8-pin size. This oscillator was carefully removed and a modified 14 pin IC socket fitted with all pins removed except pins 1,7,8,14. The new oscillator was then plugged into the socket, taking careful note of the orientation. Pin 1, marked as a dot, is pointing towards the memory as can be seen in the above picture. As always, incorrect orientation of the oscillator will result in destruction of the oscillator.

At first I tried a 40MHz oscillator, but the system would not boot at all. A 39MHz oscillator also gave no results. The next frequency I had was 36Mhz, and this worked perfectly. The system has been running at this speed for about a month now, with no complaints from the owner. It is quite possible a slightly higher frequency may still work, such as 37MHz. Note that the 68882 FPU will also be overclocked by a similar amount to the 68030.

The surface mount 68030 runs fairly warm, However, I don't believe a heatsink is really necessary due to the modest amount of overclocking available.