clock timing on 68030 processors

[Karlos]

As far as I know, 68030's were sold at 16, 20(?), 25, 33, 40 and 50MHz.

There wasn't a lot of overclocking room, some folks have got 50MHz parts to run at 60MHz I think. Trying to run a 25MHz 030 at 50MHz is not going to end well.

[Karlos]

Other than the possible glue logic / memory speed issues mentioned above there's also the package type to consider. Slower 68030 tended to be PLCC, whereas the faster ones were usually PGA.

[Karlos]

So...moral of the story is do homework on an expansion card before purchase and if you want speed, spend the extra up front.

Something like that, though I am sure there is room for improvement if you had say a 25MHz card and a same-package 33MHz part and corresponding crystal. Unless the card had very sensitive timing, you should be able to replace it. That said, a lot of the slower 030's were also surface mounted, which might make replacement fiddly unless you are experienced with SMD.