[dba-Tech] A few hardware/memory questions

Steve Erbach erbachs at gmail.com
Tue May 20 08:40:46 CDT 2008


John,

"What we have here is a failure to commun'cate"

BLAM!

Oh, yeah!

I was curious about what you said here:

» What happens if you install less than 4 gigs (only 2 gigs)?  Windows no
longer has to carve the holes out to map the memory of the video card so
you end with with ALL of that 2 gigs available as memory. «

So, if you have MORE than 2 GB of RAM, Windows will "carve holes" in
RAM but if you have 2 GB or LESS then it doesn't?  Sounds funny.  Is
there a performance boost with the mapped memory if you've got 4 GB
installed?  If so then the reverse is true if you've only got 2 GB win
no mapping?

Steve Erbach
Neenah, WI


On Sat, May 17, 2008 at 9:04 PM, jwcolby <jwcolby at colbyconsulting.com> wrote:
>  > 1.) I'm going to upgrade my pc -- was going to go all the way to 2
> gigs until the recent conversation about Windows XP not being able to
> use more than 1.2, so my question is, why pay for 2 if the system's only
> going to use 1.5?
>
> Uhhh... I think there has been a failure to communicate... (one of my
> favorite movie lines).
>
> Windows XP x32 can use up to 4 gigabytes of RAM.  Windows XP x64 can use
> ... unknown but way more than you can fit in your machine.
>
> The x32 4 gig limitation comes from the fact that using a 32 bit address
> register you can only physically access 2^32 addresses which equals 4
> gigs.  NOW, having said that, any memory that is on perepheral devices
> such as (for example) 128 or 256 megs on a video card have to be
> "mapped" into that same 4 gigs of ram space, so what happens is that
> Windows carves "holes" in that 4 gigs and "maps" the video memory into
> that hole, so that you end up with 4 gigs of memory MINUS the "mapped"
> memory from your video card.  USUALLY you will end up with something
> between 3.25 and 3.6 gigs of RAM if you install 4 gigs of memory in a
> windows x32 machine.
>
> What happens if you install less than 4 gigs (only 2 gigs)?  Windows no
> longer has to carve the holes out to map the memory of the video card so
> you end with with ALL of that 2 gigs available as memory.
>
>  > 2.) Is there a modem/wireless router combo? I'm using cable Internet.
> If I have to buy both, seems like someone would be making a single unit
> that does both by now.
>
> I don't know but the cable company provides whatever they provide.  They
> usually do not give (or at least offer) you a choice.  Most of us just
> go buy a wireless modem of our own choice to place "behind" the cable modem.
>
> John W. Colby
> www.ColbyConsulting.com
>
>
> Susan Harkins wrote:
>> 1.) I'm going to upgrade my pc -- was going to go all the way to 2 gigs until the recent conversation about Windows XP not being able to use more than 1.2, so my question is, why pay for 2 if the system's only going to use 1.5?
>>
>> 2.) Is there a modem/wireless router combo? I'm using cable Internet. If I have to buy both, seems like someone would be making a single unit that does both by now.
>>
>> Susan H.




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