[BALU] 64 bit systems

jim jgoodguy at charter.net
Fri Jun 8 00:41:42 CDT 2007

Is not the address space only 48 bits, 256 terabytes
<http://en.wikipedia.org/wiki/Tebibyte>.    (I am looking foward to
buying 1 terabyte[1000 gigabytes] surplus memory). 
and the actual Ram only 40 bit addressing or just 1 terabyte of RA.  

But the registers and data width are 64 bits are they not. 

I think the 40 and 48 restrictions are only for memory ops. 

For the most part, and I go back to 8 bit procs(8080, Z80), the big
advantages of the new generation of whatever(16,32,64) are pushing more
data around, 8 bytes instead of 4 at one chunk in the 64 bit case.  
Actual arithmetic ops are secondary in consideration. 

In addition, with the 64 AMD procs, memory control is now on chip,
better memory management.  Not related to 64 bit but a goodie as part of
the technology upgrade. 

Of course, software has to catch up, and folks that remember 8 to 16, 16
to 32 know that software will take time. 

But if you get a new chip, it is likely to be a 64 bit one going forward.


Thomas Stover wrote:
> We are running several 64bit linux servers, and only one or two 32 bit
> ones. From the server / developer point of view the big issue with 64
> bit was the limited choice of distros for a while. We even switched to
> 64bit bsd on one box for a while out of frustration. Now with options
> like centos thats really no problem. Don't expect any huge wow factor
> just from moving to 64 bit. As a developer getting to play with a new
> technology it's cool. As a nerd getting the rush from having your very
> own 64bit super computer it's cool. Other than that it's going to be a
> long while before most programs see benefits. We did have a problems
> with a raid card driver, a dual head video card, and a usb 2.0
> controller card over the years. Several closed source applications do
> not yet support 64 bit, and although they should be able to run fine
> in a 64&32bit capable linux, some don't.
> Briefly here is the skinny on 64bit:
> -first its really a lie - x86_64 is only 48 hardware bits! (so 50%
> more data can be transfered in and out of the core each clock cycle)
> -native 64bit operations (this means that for example when redesigned,
> certain kinds of complex computational algorithms could be orders of
> magnitude faster)
> -goodies like native 128bit floating point operations (this means a
> program could do some crazy dsp or something way faster) (these
> operations actually take more than one clock cycle to complete)
> -fix to the 32bit unix time problem
> -my personal favorite: mmap() files into a 64bit address space - oh yeah!
> Just get Mark to give a presentation about it. :) I spent 40+ minutes
> geeking out to his questions about it.
> Jason Sandlin wrote:
>>  How many are running a 64 bit system now. I did a while back but
>> still had issues. I was just thinking about trying ti again. Are ther
>> still many issues with running a 64bit system? Does if truly have a
>> lot of benefits?
>> -- 
>> Jason Sandlin
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