Chris is right, however its a bit easier than checking part numbers to 
figure it out.

The 4000/200 is a KA660 and uses a straight Qbus backplane. The front 
consisted of a standard dual thick skunk box bulkhead (identical to the one 
on the Mv3300/3400)

The 4000/300 introduced a new CPU "box" to the design and the backplane had 
the CPU box section on the right handside and the Q-bus slots on the left. 
This has a CPU bulkhead that is a 'door' you open up to get access to a CPU 
slot and the 4 Memory bus slots. Further, on the front of these are two 
DSSI connectors (often with terminators) to give you access to the dual 
DSSI busses available on the KA670 and above.

The KA670 was also the first CPU in that series to have an 'L' number as 
opposed to an 'M' number. (Some digit could probably tell you how modules 
got numbers but it isn't obvious to me :-)

The KA670 uses MS670 memory. Further that memory is ECC and resides on the 
Mbus in the CPU box. The KA675 (4000/400) could use MS670 memory as well. 
However the KA680 (4000/500) needed faster (and wider I believe) memory. 
For a _very_ short time as far as I can tell DEC made MS680 memory modules 
but then nearly immediately went to MS690 memory which can be used on the 
600/700 and 705. The 32MB boards were used with the 500. THe 
500/600/700/705 are all NVAX machines, the 300/400 are Rigel machines I 
believe.

Generally when I attempted to power up a KA680 with MS670 memory it didn't 
work, but it did get past the basic function test (F) in this case and got 
so far as test 30 or so before spewing a bunch of memory errors on the screen.

--Chuck

At 10:06 PM 4/15/01 +0200, you wrote:
>emanuel stiebler wrote:
>
> > Hi,
> > Just tried to upgrade my 4000/400 to a 4000/600.
> >
> > Nu success :-(
> >
> > I guess, it's simply exchanging the CPU boards, right ?
> > Anything else to do ?
>
>Well normally you can't just replace the 400 CPU board with a 600 CPU
>board, since the 600 CPUs aren't compatible to the older 200/300/400
>backplanes. There are some newer systems witch have 300/400 CPUs and
>have the newer backplane witch supports the 600 CPU. Check if your
>system has a H7206-B power controler. If it doesn't you won't be able to
>use the 600 CPU.
>
>Best Regards - Chris