What is the maximum memory that can be used under os 4.0 classic ?

[Zac67]

Ok i was searching on the internet to find info why the old kv8 max 3 motherboard that has an athlon64 3200+ can handle only 2gigabytes (or 3) of ram while having access to a 64bit processor.Answer was because of the memory controller on the motherboard.

Not really correct. The RAM controller of an Athlon64 system is integrated in the CPU.
But depending of maximum number of DIMMs / ranks and maximum supported chip density, there's a physical maximum (e.g. 3 GB for socket 754) - you don't expect an Athlon64 mobo to support 18 Exabyte, do you?

Now on the amiga i never quite understood the way memory works.There are some solutions that memory could go up to 1 giga of ram or more,and that is for 68k based s accelerators on a4000.Is it a problem of the cyberstorm ppc memory controller ?Maybe a new patch of the mach chips it has could fix it ?

Theoretically possible but will not happen.
The hardware architecture could support up to 4 GB of RAM (or even more with virtual memory), but at least OS 3.x limits this to 2 GB.

[Zac67]

OS4 for CSPPC just accepts CSPPC local memory. Motherboad&Zorro memory modules are completely ignored. Joerg Strohmayer decided that Motherboad&Zorro memory support should be dumped in favour of swap memory (even thought no OS4 classic version with stable swap existed)

Somewhat comprehensible - but it'd be much smarter to use currently ignored RAM for swapping - though slow it's way faster than any HDD.

[Zac67]

No need to 'hack' anything up. You can probably just AddMem unsupported RAM to the memory pool - but it'll be sloooooowwww...

(I assume there's currently no AddMem tool for 4.x but it can't be hard to do, as long as 68k RAM is also visible to PPC. Probably the smartest way would be to use virtual memory and swap to the slow RAM.)