I found on ebay someone selling Nec Z80.I bought 2 of them because i have bought 3 spectrum machines recently,and for spares and repairs i would want to use those z80 from nec(i really hope i never have to use them!).

However i have my 2 beloved msx machines,a philips msx2 vg 8235,and a philips nms 8280.Both are in great shape.But in the unlikely event that i would ever have to change the z80 of msx would the nec z80 be able to replace the zilog z80?

In theory nec is a compatible clone of zilog.However i would want to know more.

I found this information regarding the nec z80
http://www.cpu-world.com/CPUs/Z80/NEC-D780C-2.html

Thank you

I wouldn't worry about the Z80 that much. You can still get "new old stock" ones from several places (Futurlec sell them for $2). So if you want spares, just buy new ones. No need to bother with the NEC chips from the Sinclair. If you want to worry about parts, worry about the dedicated Yamaha chips that are in the MSX. Those will be hard to get and even harder to replace.

There's no difference between a NEC or Zilog Z80. I doubt that all MSX computers use Zilog chips, since the Z80 was available from a lot of second sources, and NEC was one of the early ones.

I have at least one MSX computer with a processor from Sharp. Also, I have a Spectrum with a real Zilog. So even Sinclair used both.