Yes you're right ,they are modular. The change christensen refers to is the shift from companies that built whole computers, like IBM - to the IBM pc , which w

Yes you're right ,they are modular. The change christensen refers to is the shift from companies that built whole computers, like IBM - to the IBM pc , which was an assembly of parts from different companies. My guess is that at that time , the pc-XT came with memory chips that weren't soldered , but in sockets. At that context that didn't mean much loss of performance. That habit of pluggable memory stuck. I'm not sure you lose much performance due to it. And if we're talking about integrated memory - intel does have caches. Probably those are the best ways to deeply integrate memory. And regarding CPU and board: it would be quite hard to integrate chips and board. There's was one attempt i know but it failed as far as i know. It's complex and not economical, but it does offer great performance.