* It appears the RAM exists under the Disc Wizard ROM when it's enabled. The code assumes it can use the stack to store the current register settings at the point the NMI is triggered, and this may be located under the Disc Wizard ROM.
* It appears that when the CPC is reset, the Disc Wizard ROM is disabled.
Now, thanks to Jose Leandro, the hardware specialist of the spectrum, with his famous page :
http://trastero.speccy.org/cosas/JL/JL.htm
We can know more about this hardware.
== Pictures ==