Great news for all 030 speed demons:
I have just successfully clock chipped my 50 MHz Daystar Universal PowerCache with FPU to 55 MHz!
Speedometer 4.0.2 shows that all processor-related functions are now operating 10% faster than before modifying the Daystar card.
The mod was achieved by substituting a 55 MHz oscillator in place of the 50 MHz unit on the PowerCache.
I have not been able to find any reference to clock chipping a Daystar Universal PowerCache, and believe that I am the first to report it.
I currently have this card running in a IIsi and it seems to be stable (System Software 7.1). For an additional boost, I have upclocked the IIsi's data bus to 25 MHz (up from the stock 20 MHz).
I am going to continue testing the card with progressively faster oscillators to see what the maximum usable frequency is before it becomes unreliable. I'll have to attach a heat sink to both the 030 processor and the 68882 FPU on the PowerCache, as these already run hot enough to burn one's fingers even at the stock 50 MHz clock speed. I am hopeful that proper cooling will allow this card to tolerate 60 MHz or even higher.
As for the data bus on the IIsi, it will be interesting to see what effect raising its frequency will have on the ability to boot the Daystar card. Is there a frequency above which the PDS slot in the IIsi becomes unusable? The only info I've found so far about maxing out the IIsi's bus speed is from Marc Schrier's page; he states that the IIsi's floppy drive controller can become unstable when the data bus is pushed above 28.3 MHz on some units.
I am delighted to find that this worked and welcome feedback and suggestions from the Listas!