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3.25 gb limit, even with 64-bit OS, why?

post #1 of 17
6/5/08 at 2:11am
Thread Starter 
I just installed my 4 gb of RAM in my Inspiron 9400, fully aware and knowing in advance that I won't be able to use more than 3.25 of it with my Vista Ultimate 64-bit OS...

My question is: WHY? Is it because the Bios can't address the memory in 64-bit? Just for curiosity, is there a way to make the OS bypass the BIOS (If it's the cause) and fully use the 4 GB?

Thanks for satisfying my curiosity...
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post #2 of 17
6/5/08 at 2:25am
I believe the 945 only has an addressable space of 4 GB, so you won't be able to access the reserved part.

(To address the "full" 4 GB, chipsets usually remap the reserved space to above the 4 GB space, so if the chipset can't do the mapping, it won't be able to access the "full" memory space.)
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post #3 of 17
6/5/08 at 3:17am
Thread Starter 
Quote:
Originally Posted by Revenent View Post
I believe the 945 only has an addressable space of 4 GB, so you won't be able to access the reserved part.

(To address the "full" 4 GB, chipsets usually remap the reserved space to above the 4 GB space, so if the chipset can't do the mapping, it won't be able to access the "full" memory space.)

Of course!!!!! You're right.... Why didn't I though of that....lol

Thanks a lot!
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post #4 of 17
6/6/08 at 5:28am
The 945 chipset in order to support Core Duo and Core Solo CPUs (which are 32bit only) had to have memory address space limited to 4GB. The newer chipsets, designed for 64bit CPUs only, don't have this issue.
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post #5 of 17
6/9/08 at 1:24pm
I also own a Inspiron 9400 and I would love to upgrade to 4GB.
But know u are telling me i cant use the last 0,75GB, NEVER??
That is SO sad.

Would this memory work (besides the size)?
Kingston DDR2 HyperX SO-DIMM PC5300 4GB, KIT of 2x2GB, CL4-4-4-12, 200pin
Unbuffered and NO ECC, 1.8v
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post #6 of 17
6/9/08 at 1:26pm
Yeah, that'd work.
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post #7 of 17
6/9/08 at 3:24pm
Is there any point (except for the 0.25gb increase) in having 2+2gb instead of 2+1gb? Dual Channel?
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post #8 of 17
6/9/08 at 3:33pm
Considering the price of memory is so cheap, IMO the Dual channle 4 GB Kit is the way to go.
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post #9 of 17
6/9/08 at 4:05pm
There's not going to be a HUGE difference between single-channel 3GB (2GB+1GB) over dual-channel (2GB+2GB) but there is a slight difference. It's not much to write home about (about a 1-3% real-world difference) but, like Dave said, considering how cheap memory is, there's really no reason to go the single-channel route.
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post #10 of 17
6/9/08 at 5:05pm
Quote:
Originally Posted by MuRRe_C View Post
I also own a Inspiron 9400 and I would love to upgrade to 4GB.
But know u are telling me i cant use the last 0,75GB, NEVER??
That is SO sad.
True and untrue. While I don't think at all that the system uses the whole 0.75 GB (or even close to it) memory it reserves, it does use a decent fraction of it for your hardware. So, while the memory is not available to you at user-level, its definitely a requirement machine-level. That is unless you think you can function without a keyboard, lcd, etc.
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post #11 of 17
6/9/08 at 5:28pm
Like i said before im thinking about buying

Kingston DDR2 HyperX SO-DIMM PC5300 4GB, KIT of 2x2GB, CL4-4-4-12, 200pin

Is there any other memory that is MUCH better than this or will this be good? (I will pay around 183 dollars, i live in Sweden so thats why)
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post #12 of 17
6/9/08 at 6:02pm
Quote:
Originally Posted by Fenuxx View Post
Yeah, that'd work.
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post #13 of 17
6/9/08 at 6:28pm
Quote:
Originally Posted by Fenuxx View Post
Yeah, but is it a good choice or is there any other that is better for the same price or is it marginal?
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post #14 of 17
6/9/08 at 7:37pm
It's all virtually the same. The only real difference of choice is getting a brand you like. Getting "extreme" memory won't offer any benefits. You can't overclock the FSB/RAM, so there's really no difference.
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post #15 of 17
7/1/08 at 2:01pm
Actually after installing Vista Ultimate 32bit it's reporting 4GB of ram.
Is something wrong????

HELP
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post #16 of 17
7/1/08 at 2:48pm
Quote:
Originally Posted by MuRRe_C View Post
Actually after installing Vista Ultimate 32bit it's reporting 4GB of ram.
Is something wrong????

HELP
Vista SP1 is now reporting actual installed values rather than visible values.

Previously, different components would report different values (System Information would return different values from Task Manager, etc, etc.), and people decided that a consistent value would be less confusing to users.

I'm not sure, but Task Manager may still report the "true" in-use/remaining physical memory values.
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post #17 of 17
7/1/08 at 7:31pm
Thread Starter 
Since Vista's Service Pack 1, the OS report the quantity of memory Installed, instead of reporting the amount of "usable" memory. If you're having SP1 and you take the OS number, it's normal!
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