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The Grumpy Editor goes 64-bit

The Grumpy Editor goes 64-bit

Posted Apr 15, 2004 2:15 UTC (Thu) by tjc (guest, #137)
Parent article: The Grumpy Editor goes 64-bit

The fact is, 32 bits suffice for almost every quantity we need to manipulate with computers. The exception, increasingly, is memory. We have hit the point where we are running out of address space.

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. When it comes to computers, I'm always an advocate of doing things in a minimalist sort of way. :-)


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The Grumpy Editor goes 64-bit

Posted Apr 15, 2004 2:20 UTC (Thu) by corbet (editor, #1) [Link]

"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.

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'

The Grumpy Editor goes 64-bit

Posted Apr 15, 2004 2:28 UTC (Thu) by dlang (subscriber, #313) [Link]

the Opteron 64 bit approach is actually simpler to use for both new and legacy software then the 36 or 40 bit memory extentions that Intel is providing, and it performs better as well.

whose who have been around long enough to remember EMS memory on the 8088 machines will find the Intel PAE memory concept very familiar, and there is a GOOD reason why nobody uses EMS memory anymore


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