it means I'm totally the wrong dude to ask

So yeah, Westmere sounds just about right. I think the key aspect is "integrated memory controller" or "no Front Side Bus" as we think that this is why the older 8-core doesn't perform well. This is just based on intelligent guessing though, because it's the best answer we got for its poor multicore scaling with Diva.

A quick stroll on Wikipedia says we're using Gulftowns in our faster machines and Harpertown on the loser.

Great info, helps me whittle things down a bit. There's so many refurbished mac 1,1 and 3,1 models on ebay it's a quite taxing process for someone like me who's only semi-literate when it comes to building computers. especially when you're trying to be as future-proof as possible.

Apologies for the minor derail - back to scheduled programming