Turbo 7 MHz is coming again
Hehe, wouldn't that be nice? But no, to my knowledge, you'd still miss some important parts; the S1990 (with the Z80 built-in), different memory structure, so I suggest you'd go for some eBay auction 
What is this Turbo 7 mhz ? A kit to double the clock frequency or an expansion board containing a different processor ? Excuse me if this is a trivial question, but I am not very familiar with the upgrades an expansions post 1990.
I have schematics of a 6 MHz board that are from 1989, so that should be old enough for you to be familiar with It's probably similar to that. My guess is that 6 MHz was as fast as any Z80B would go in 1989.
By the way, that only contains three easily obtainable 74LSxx chips that shouldn't take months to source ($0.84 for the three from Futurlec).
I have schematics of a 6 MHz board that are from 1989, so that should be old enough for you to be familiar with It's probably similar to that. My guess is that 6 MHz was as fast as any Z80B would go in 1989.
By the way, that only contains three easily obtainable 74LSxx chips that shouldn't take months to source ($0.84 for the three from Futurlec).
Could you post the schematics somewhere?
Maybe send them to Hansotten.
Ah very nice! I just ordered one by e-mail 
But I have another question... is it possible for you to build it into a Sony hb-f700p which is upgraded to a MSX2+?
I've got about a hundred Z80B CPUs here. Anyone interested in the whole lot? I'd like to trade them instead of selling them. Anyone's welcome, but I'm not going to sell them one by one. It's all or nothing 