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The Grumpy Editor goes 64-bit

The Grumpy Editor goes 64-bit

Posted Apr 15, 2004 2:20 UTC (Thu) by corbet (editor, #1)
In reply to: The Grumpy Editor goes 64-bit by tjc
Parent article: The Grumpy Editor goes 64-bit

"It seems that 32-bit processors with 36 or 40-bit address buses could prolong the life of 32-bit (instruction) processors for some time."

That, of course, is exactly what modern Pentium processors are. You can put 64GB of memory into such a thing, but that road leads to all the high memory hassles that the kernel hackers have been having so much fun dealing with. Addressing more physical memory can be (and is) done; the real problem is that you need larger virtual addresses. And that really forces a larger word size or your pointer arithmetic slows to a crawl.

Unless, of course, you want to get back into multiple memory models and "near" and "far" addresses. Personally, I don't miss those days at all.


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The Grumpy Editor goes 64-bit

Posted Apr 15, 2004 2:38 UTC (Thu) by tjc (guest, #137) [Link]

Unless, of course, you want to get back into multiple memory models and "near" and "far" addresses. Personally, I don't miss those days at all.

Nor do I, and to be honest, I'm not really "up" on the details of memory management in Linux. But it seems to me that going to a 64-bit address space isn't free either. For one thing, if you use hierarchial paging, either the page table is going to be huge, or else you're going to end up with about 6 levels of indirection, which has got to be slow too. My best guess is that they hash the page table somehow?

Anyway, I'll let you see how it goes, and I'll move to 64-bit when it's safe - say in 3 or 4 years. :-)

The Grumpy Editor goes 64-bit

Posted Apr 15, 2004 4:07 UTC (Thu) by smoogen (subscriber, #97) [Link]

Its not really the memory management of the Linux box as much as the memory management of the PC architecture itself. There are limits to where a PCI bus, BIOS, and other things can be 'hacked' to working and each time more memory is extended it gets more hackish than a 'clean-minimalist fix'


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