In <Pine.LNX.4.10.10005031706140.1928-100000@localhost.localdomain> Mark Zealey (kernel@itsolve.co.uk) wrote:
> On Wed, 3 May 2000, Jamie Lokier wrote:
>> When AMD releases their IA32 processors with 64 bit extensions, perhaps
>> that will support more than 4GB per process too.
>>
>> You can of course _access_ much more than that per process. And the
>> total RAM shared between all processes is not subject to the 4GB
>> limitation. On Pentium Pros you can use 64GB total RAM.
> Can't you get 4TB on i386's? using page gran. That's what it says in 'the
> indespensable PC hardware book'.
No. You are mixing things. There are few different types of memory:
1. physical RAM - up to 4GiB on i386-Pentium, up to 64GiB on PPro
(limiting factor is address bus size).
2. virtual RAM for process without usage of segments - up to 4GiB
but if you'll define kernel as separate process then EACH syscall
will be VERY expensive - not an option, so: 3GiB for process,
1GiB for kernel
3. virtual RAM for process with usage of segments - up to 4TiB but
so unmanageable that it not useful for anything apart of Intel
press-releases :-)
P.S. And total virtual RAM for ALL processes can easily exceed 4GiB, 64GiB
(in theory; on practice Linux supports "just" up to 8 swap partitions 2GiB
each) and even 4TiB - it's not hardware limitation but rather OS design
limitation...
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