I have been trying to understand a bit more about this new chip. From what I can see, some people say that it's not real 64bit. (and allow a much more generous amount of RAM). Is that understanding correct?
I do expect better performance overall though as I can see that overall, Intel has added faster bus, bigger I/O pipe, use of DDR2 RAM etc.
But what I am after is: if you strip away all the marketing hype, is it simply a 32bit Xeon CPU 'hacked' to run 64bit applications and to support more RAM?
Last edited by sprintserve; 05-03-2005 at 04:43 AM.
You are on the point. The Xeon EM64T does not even support more ram than old xeon or p4. It can only do 36 bit physical address, which means 64GB of ram maximum, the same as old Xeon with PAE. It did add 64 bit registers and support 64 bit virtual address, it's a copy of the AMD64 instructItion set.
But AMD64 is a whole new architecture designed from begining to support
1) true 64 bit computing
2) multi-core --- the opterons, even single core ones has a crossbar builtin for multiple cores.
3) direct connect architecture: eliminate the front bus, and direct connect cpu to memory, cpu to I/O and CPU to CPU. it is called hypertransport and cache coherent hypertransport.
4) builtin data execution prvention, so buffer overflows are protected
5) support for virtualization, run multiple OSes the same time
INTEL had maintained that 64 bit was not needed when AMD released opteron, INTEL also said they had 5 teams studying how to make x86 to be 64 bit and concluded that it was impossible. But AMD made it happen, now INTEL is playing catch up.