[phenixbb] fem command/memory error

Tim Gruene tg at shelx.uni-ac.gwdg.de
Wed May 14 09:14:19 PDT 2014


Hi Roger,

not quite 16GB:

32 bit gives 2^ 32 / 1024^3 GB = 4 GB
64 bit: 2^64 / 1024^3 = 17179869184 GB = 16 Exa B

Cheers,
Tim

On 05/14/2014 05:13 PM, Roger Rowlett wrote:
> 4 Gb is the limit of addressable memory for 32-bit machines. The amount
> of usable memory (RAM) is anywhere from around 2-3 Gbyte depending on
> hardware configuration. Some hardware (e.g., a graphics card) reserves
> memory space for itself, decreasing the amount available for usable RAM.
> 
> I believe all relatively modern (last 5-10 years?) CPUs are 64-bit
> capable. A 64-bit machine should be able to address 16 Gbyte of memory.
> (Minus hardware deductions for usuable memory space.)
> 
> Cheers,
> 
> _______________________________________
> Roger S. Rowlett
> Gordon & Dorothy Kline Professor
> Department of Chemistry
> Colgate University
> 13 Oak Drive
> Hamilton, NY 13346
> 
> tel: (315)-228-7245
> ofc: (315)-228-7395
> fax: (315)-228-7935
> email: rrowlett at colgate.edu
> 
> On 5/14/2014 11:05 AM, Nathaniel Echols wrote:
>> On Wed, May 14, 2014 at 1:44 AM, Matteo Colombo
>> <Matteo-Maria.Colombo at ibs.fr <mailto:Matteo-Maria.Colombo at ibs.fr>> wrote:
>>
>>     My OS is Ubuntu precise 12.04 LTS, system 32 bit
>>
>>
>> One note of caution: if you are running a 32-bit architecture or OS,
>> upgrading the memory may not help, because it will be limited in how
>> much it can address at once.  (I forget if the limit is 2GB or 4GB; it
>> may be OS-dependent.)  At this point I would recommend using 64-bit
>> for everything if possible, and especially not purchasing any systems
>> that are 32-bit only.  (Are these even sold any more?)
>>
>> -Nat
>>
>>
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> 
> 
> 
> 
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-- 
Dr Tim Gruene
Institut fuer anorganische Chemie
Tammannstr. 4
D-37077 Goettingen

GPG Key ID = A46BEE1A

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