Re: Using >1GB RAM
Albert D. Cahalan (acahalan@cs.uml.edu)
Tue, 13 Jan 1998 15:19:16 -0500 (EST)
>> Perhaps a new architecture, p6big. Mostly it would have symbolic
>> links into the i386 code. The page tables would use the weird
>> 36-bit Pentium Pro features (64 GB physical memory). Segments
>> would be used everywhere. All the old segment registers get used
>> as originally intended, but to go past 4 GB in 1998.
>>
>> For really big processes, gcc needs to learn about 48-bit far pointers.
>
> no, the PPro 'bigphys' feature extends physical memory space to 64G
> (actually extends it to 64 bits, but i guess the CPU itself is 64G
> limited), but logical address space will stay pure 32 bits.
The Pentium Pro feature extends physical memory, while the old
segmentation hack extends virtual memory to 48 bits.
The only 32-bit limits would be the stack, the code, and the
size of individual data objects. Total data can be huge.
> hm, is such 'above 4G' memory PCI DMA-able? it's pretty much
> useless if it doesnt integrate well into PCI.
That needs to be solved for the Alpha anyway.
It is just like the 16 MB ISA limit, which is already solved.
History repeats itself again.