Twin-charging was just something that several Japanese manufactures played with.
The supercharger negates turbo lag at lower rpm, and the turbo utilizes wasted energy to provide boost, and relieve supercharger power draw at higher rpm.
Toyota also did it on the GX81 Chaser sedan.
And HKS made a kit for the 4AG for twin-charging it.

Both have to be sized correctly for the engine they are going on, and both would make boost by them selves, without the other,
but over all performance would not be as good.

In the end, nobody does it any more. I guess because of the cost and complexity of the systems.

Nissan only built 500 of the super-turbo March cars per year.
I believe it was just to meet production requirements of a class of racing there in Japan.

Actually DD,
the AMR500 is an excellent choice for a 1000cc engine, and even larger.
Any 4-stroke engine only displaces half it's advertised volume per revolution.
A 1000cc engine only takes in 500cc each time the crank turns once.
An AMR500, wich is used on several small displacement Japanese cars,
can be overdriven to make excellent boost on a small 4-cylinder.

If it is driven 1.5 times crank speed, it will produce around 7-8 psi on a 1 liter engine.

And they can be driven way faster than that.
We have tested them up to 18,000 rpm.
So if your engine only revs to 9000, the AMR500 cna be driven twices crank speed,
and produce about 15 psi boost.

I have even seen these applied to 1600cc bug engines, driven twice crank speed,
and make around 4 psi.
Nice compact package, that made a good performance gain.