Author Topic: Why do I only have 3gb ram and not 4gb?  (Read 20429 times)

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Offline RejZoR

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Re: Why do I only have 3gb ram and not 4gb?
« Reply #30 on: July 22, 2009, 03:51:04 PM »
So why is it that A lot of people have trouble running 32bit programs on 64bit OS =o?

Bollocks. You'll only have problems with really ancient stuff that was designed with early 32bit in mind or even 16bit (mostly games).
But other than that i have yet to find "stuff" that "many users" have problems with. Because i'm on 64bit for the second yer and i never had any problems.
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Re: Why do I only have 3gb ram and not 4gb?
« Reply #31 on: July 23, 2009, 01:36:15 PM »
Back to RAM.  I saw this website(http://www.mydigitallife.info/2008/06/04/differences-and-advantages-between-32-bit-x86-vs-64-bit-x64-windows-vista/) comparing 32 and 64 bit and they said " All 32-bit versions of Windows Vista can access up to 4 GB of RAM."
Is this true only of Vista systems? 
RoRo

Offline Lisandro

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Re: Why do I only have 3gb ram and not 4gb?
« Reply #32 on: July 23, 2009, 02:11:53 PM »
Back to RAM.  I saw this website(http://www.mydigitallife.info/2008/06/04/differences-and-advantages-between-32-bit-x86-vs-64-bit-x64-windows-vista/) comparing 32 and 64 bit and they said " All 32-bit versions of Windows Vista can access up to 4 GB of RAM."
Is this true only of Vista systems? 
No, for all 32bits systems (XP, etc.).
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Re: Why do I only have 3gb ram and not 4gb?
« Reply #33 on: July 23, 2009, 02:33:08 PM »
Then why do some 32 bit systems says they can only use 3 GB RAM? 

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Offline DavidR

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Re: Why do I only have 3gb ram and not 4gb?
« Reply #34 on: July 23, 2009, 03:08:06 PM »
I wouldn't even worry about this, if you have 4GB of RAM the 32 bit OS will use as much as it can handle.

Here is an extract from an article in the Windows Secrets newsletter by Scott Dunn who is vastly more experienced than I in this matter.

Quote
Here's the full story behind how much RAM a given system can handle.

First, there's hardware. Each system has a fundamental physical limit on the amount of memory it can accommodate. Most PCs and laptops sold today have a 32-bit internal architecture.

That means that the computer can generate distinct, internal memory addresses that start at zero and go up to a binary number (ones and zeros) that's 32 digits long. Mathematically, that's 2 to the 32nd power — or about 4.2 billion memory addresses to play with. This translates to about 4GB.

The 32-bit limit is fundamental and real: a 32-bit PC cannot generate an internal 33-bit address, so once all 4.2 billion addresses are in use, you're done. About 4GB is all you get for RAM in a 32-bit PC, period.

Why "about" 4GB? Why isn't it an exact number? That's because the PC uses its total memory space not just for RAM but also for such housekeeping chores as remembering your hardware and maintaining internal scratchpads and "stacks."

Any memory addresses remaining unused after the housekeeping requirements are met will be available for use as general-purpose memory. This represents the amount of RAM you can actually use.

It's not unusual for a PC to need almost a full gigabyte of addresses for internal use, so putting 4GB of RAM into a standard 32-bit system usually nets around 3.2GB of usable RAM. The rest of the 4GB of RAM is there, but the system has no way of accessing the memory because your PC has run out of internal addresses.

There's a further complication: many current systems — especially laptops — don't even try to allow the absolute theoretical maximum RAM due to such design considerations as cost, heat, power consumption, and size.
<snip>
That's the hardware side of things, but standard 32-bit software also shares the same mathematical ceiling that 32-bit hardware has and is likewise limited to recognizing no more than 4GB of address space.

That's all the RAM that standard 32-bit XP or Vista (or 32-bit Linux or Macs, for that matter) will ever "see" on standard 32-bit hardware. No matter how you slice it, 2 to the 32nd equals 4GB. That's all there is.

Note that some server-oriented 32-bit systems can use "address extensions" to perform a sleight-of-hand that tricks the operating system into thinking it's working within the normal 4GB address space when the system is actually tap-dancing madly behind the scenes to allow access to somewhat more.

Scott Dunn covered some of these techniques in his excellent column in the Dec. 18, 2008, newsletter titled "Access more memory, even on a 32-bit system." But even though the techniques Scott describes let you partially sidestep current memory constraints, they don't change the fundamental 4GB cap for 32-bit architectures.

The real answer for more memory space is to move to 64-bit hardware and software. The mathematical ceiling for 64-bit hardware is an astonishing 16EB (exabytes) of memory space — 16 quintillion bytes. That's a whopping 16 million terabytes, or 16 billion gigabytes. That ought to accommodate your MP3 collection.
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Re: Why do I only have 3gb ram and not 4gb?
« Reply #35 on: July 23, 2009, 03:15:22 PM »
Isn't it an UAC problem?
I don't think so. 

It is a registry item permission problem.

I tried to navigate to the item in the registry using regedit.exe Run as administrator and take ownership and grant Full access but I was denied permission.

could still be a UAC issue. Some programs just don't run fine at all if you installed them with UAC on. Granting them admin privilege afterward doesn't help. You must install them with UAC off (probably because they don't support virtualization). You can always turn UAC back on once the install's done. That's what I had to do for a couple (few) of programs.

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Re: Why do I only have 3gb ram and not 4gb?
« Reply #36 on: July 23, 2009, 03:18:42 PM »
Back to RAM.  I saw this website(http://www.mydigitallife.info/2008/06/04/differences-and-advantages-between-32-bit-x86-vs-64-bit-x64-windows-vista/) comparing 32 and 64 bit and they said " All 32-bit versions of Windows Vista can access up to 4 GB of RAM."
Is this true only of Vista systems? 
RoRo


any 32 bit version of Windows will be able to detect up to 4GB of RAM, but won't be able to use more than 3. As to "many people complaining about 32 bit software issues on 64 bit OS", that's bs  ;)

roro

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Re: Why do I only have 3gb ram and not 4gb?
« Reply #37 on: July 24, 2009, 10:58:11 AM »
Thank you Logos and DavidR.
So, if I had only 3 GB of RAM, my computer would run the same, because although it can access 4 GB, it can only use 3 GB.  Tt is interesting that they will sell 4 GB without telling you this at Dell.  If I am using shared RAM for Video does that decrease the 3 GB usable for the rest of the system, or will that be taken for the 4 GB that I have accessible?

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Re: Why do I only have 3gb ram and not 4gb?
« Reply #38 on: July 24, 2009, 11:18:06 AM »
if the video memory is shared, that will of course decrease the 3GB usable limit (on board video memory, ie RAM that physically belongs to your video card, is fully usable on top of that, whatever OS you run, 32 or 64 bit).

roro

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Re: Why do I only have 3gb ram and not 4gb?
« Reply #39 on: July 24, 2009, 12:14:51 PM »
Thanks Logos,
I now understand better the availability and uses of RAM.  This forum is such a great place to learn.

RoRo

Offline DavidR

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Re: Why do I only have 3gb ram and not 4gb?
« Reply #40 on: July 24, 2009, 03:33:28 PM »
Thank you Logos and DavidR.
So, if I had only 3 GB of RAM, my computer would run the same, because although it can access 4 GB, it can only use 3 GB.  Tt is interesting that they will sell 4 GB without telling you this at Dell.  If I am using shared RAM for Video does that decrease the 3 GB usable for the rest of the system, or will that be taken for the 4 GB that I have accessible?

Technically no (outside of the video shared memory requirement), because of what was said an element of that RAM is used by the OS for its housekeeping which further reduces the RAM available to programs.

Quote from: Extract of previous quote
Why "about" 4GB? Why isn't it an exact number? That's because the PC uses its total memory space not just for RAM but also for such housekeeping chores as remembering your hardware and maintaining internal scratchpads and "stacks."

Any memory addresses remaining unused after the housekeeping requirements are met will be available for use as general-purpose memory. This represents the amount of RAM you can actually use.

It's not unusual for a PC to need almost a full gigabyte of addresses for internal use, so putting 4GB of RAM into a standard 32-bit system usually nets around 3.2GB of usable RAM. The rest of the 4GB of RAM is there, but the system has no way of accessing the memory because your PC has run out of internal addresses.

So starting with 4GB rather than starting with 3GB would leave you more after the housekeeping and shared video requirements are taken into account.
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