Linked by Thom Holwerda on Fri 30th Oct 2009 12:07 UTC
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Edit:Sorry, I was wrong. Only the Z and N don't have 64bit.
But with less than 4GB 64bit is toally pointless. You waste a lot of CPU cache for nothing. The system will be way slower.
But with less than 4GB 64bit is toally pointless. You waste a lot of CPU cache for nothing. The system will be way slower.
Strictly speaking, don't the kernel tradeoffs begin above around 800MB? Bounce buffers and such? And don't forget all the extra registers that come with X86_64.
Personally, I think that 64 bit kernel with 32 bit user space, with individual 64 bit apps deployed strategically, is really optimum for many situations. The kernel has all the memory management advantages of 64 bit. But without the memory hit of 64 bit user space pointers, except where 64 bit can really help. As it *which* 64 bit apps to strategically deploy, if any... I'm not certain. And, of course, it depends upon the exact situation.
Yes, you are right. 64bit kernel and 32 bit apps would be optimal in most cases.
AFAIK modern CPUs get their speed from running stuff in cpu cache and 64bit pointers etc take way more cache memory.
I don't know that much about CPU design, but I think the current design of X86 and AMD64 has a lot of limitations because of backwards compatibility.
Maybe when FOSS gets more popular AMD or Intel will introduce an "X86 unleashed" mode where you have can 16 64bit registers and 32 bit pointers and GCC and go wild with its optimizations. Might be just a brainfart, though.






Member since:
2006-01-04
Err, the Atom is a low end-chip. So no AMD64.
That is market segmentation for you.
Edit:Sorry, I was wrong. Only the Z and N don't have 64bit.
But with less than 4GB 64bit is toally pointless. You waste a lot of CPU cache for nothing. The system will be way slower.
Edited 2009-10-30 16:59 UTC