4gb address space limitation for i386

[Garrett Cooper]

User Bobby wrote:
> Ok thank you all for your replies.
>
> I'm thinking I can't use amd64 on a PIII, right?
>
> So, given that I'm stuck with this particular piece of hardware, my 
> only real option is to begin down the long and scary road of PAE.  Yes?
>
> Bob
>
> On Thu, 30 Aug 2007, youshi10 at u.washington.edu wrote:
>
>> On Thu, 30 Aug 2007, User Bobby wrote:
>>
>>> I have an IBM xSeries 350 4xPIII with 5.5gb of RAM, and see that 
>>> only about 3.5gb is being used under the i386 port.  I've been 
>>> looking through the
>>> archives to try and figure out what the root of the problem is and I 
>>> amn't
>>> quite sure I know which part of the situation is the real problem.
>>>
>>> Is it a limitation of the i386 port?  That is to say, if there were 
>>> a specific PIII (i686?) port, would this problem be overcome?  Or is 
>>> it a hardware limitation?  Is it necessary to use a not-clean method 
>>> to access the extra address space (is this what PAE is?), and 
>>> there's no clean
>>> way around it, regardless of the port?
>>>
>>> I was looking at building a PAE kernel, but was discouraged by the 
>>> lack of usb and certain SCSI support, both of which I'd really like 
>>> to have (in the case of SCSI, need to have).  Is this lack of 
>>> support because of an inherent difficulty in the hardware, or could 
>>> it be overcome in a stable way with modification of the device 
>>> driver code?
>>>
>>> My basic (and very hypothetical) question - if I had unlimited time 
>>> and knowledge (I have limited both), what direction would I take to 
>>> get access to all 5.5gb of RAM on this particular computer?
>>>
>>> Thank you,
>>> Bob
>>
>> It's a limitation of the basic i386 architecture; you have to use 
>> i386 with PAE, or better yet use amd64, because those architectures 
>> support memory address sizes beyond 32-bits.
>>
>> Cheers,
>> -Garrett
Correct.
-Garrett