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what could ruin dual-channel?

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March 10, 2008 9:26:11 PM

I'm using xp-pro, with 2gb DDR3.
But xp can only "see" up to 4gb max (32bit), I have got a 3870X2 with 1gb memory. So is it true that if I insert 4gb of memory only 3gb will be used (because of the 1gb of the Graphicscard)?

second question, if I use 3 modules of 1gb, will I have Dual-channel? or is 3gb non-dual-channel better the 2gb dual-channel anyway? (In other words, does the last module of memory destroys the dual-channel effect of the first 2 modules)

More about : ruin dual channel

March 10, 2008 10:46:02 PM

robertdv said:
I'm using xp-pro, with 2gb DDR3.
But xp can only "see" up to 4gb max (32bit), I have got a 3870X2 with 1gb memory. So is it true that if I insert 4gb of memory only 3gb will be used (because of the 1gb of the Graphicscard)?

second question, if I use 3 modules of 1gb, will I have Dual-channel? or is 3gb non-dual-channel better the 2gb dual-channel anyway? (In other words, does the last module of memory destroys the dual-channel effect of the first 2 modules)



Wow, where to start on this? Ok, here goes:

Regarding the amount of memory that your 32-bit operating system can see (Windows XP-Pro 32-bit), it has nothing to do with the amount of memory on your graphics card. In 32-bit, there is only enough memory address space for exactly 4GB, and a certain portion of that is taken up by the operating system itself. So, in a 32-bit OS, you'll only be able to 'see' between 3-3.5GB of memory, depending on how the operating system is configured (again, we're talking about system memory here, graphics memory has nothing to do with it). A lot of people go ahead and install 4GB memory (in dual channel) in their system even when using 32-bit OS and just live with the 3-3.5GB that they are able to utilize. Personally, my choice is to go with 2GB of memory for now, and to later buy another 2GB of memory and a 64-bit OS at the same time.

Now, for the dual channel question. If you're going to go for 3GB of memory, all you have to do is have 2x1GB for the first 2GB of memory, and 2x512mb for the 3rd GB. So you have 2 sticks of 1GB in dual channel mode, and 2 sticks of 512MB in dual channel mode, for a total of 3GB all in dual channel.

Hope this clears things up.
March 10, 2008 11:41:58 PM

I agree with what mtyermom said but if you want to save money 2 gigs is still enough for most games or applications unless you have a lot of stuff running in the background or are editing a lot of video etc.
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March 11, 2008 1:30:31 AM

mtyermom said:

Regarding the amount of memory that your 32-bit operating system can see (Windows XP-Pro 32-bit), it has nothing to do with the amount of memory on your graphics card.

That is actually wrong. I could go into a lengthy description regarding the hows and whys but others already did so. Here is an excerpt from an official HP paper regarding the 32bit limitations (source).

"The PCI memory addresses starting down from 4 GB are used for things like the BIOS, IO cards, networking, PCI hubs, bus bridges, PCI-Express, and video/graphics cards. The BIOS takes up about 512 KB starting from the very top address. Then each of the other items mentioned are allocated address ranges below the BIOS range. The largest block of addresses is allocated for today’s high performance graphics cards which need addresses for at least the amount of memory on the graphics card. The net result is that a high performance x86-based computer may allocate 512 MB to more than 1 GB for the PCI memory address range before any RAM (physical user memory) addresses are allocated."

PAE (Physical Address Extension) can be used to address more than 4GB while using a 32bit operating system. The drawback is, that applications have to be programmed specifically to make use of that added address space and most aren't.

mtyermom said:

So, in a 32-bit OS, you'll only be able to 'see' between 3-3.5GB of memory, depending on how the operating system is configured (again, we're talking about system memory here, graphics memory has nothing to do with it).


See above.

mtyermom said:

A lot of people go ahead and install 4GB memory (in dual channel) in their system even when using 32-bit OS and just live with the 3-3.5GB that they are able to utilize. Personally, my choice is to go with 2GB of memory for now, and to later buy another 2GB of memory and a 64-bit OS at the same time.

That is an interesting proposal, but let me make sure everyone understands the facts this proposal is based on.
Depending on the amount of PCI/USB/PCIe/etc. devices the amount of memory addressable will be reduced from 4GB down. Depending on those factors the usable amount tends to be between 3.5 GB and, in extreme cases, barely above 2GB.
A 64bit operating system has a higher address range, but devices will still take away address space from the top, which is roughly (according to Microsoft) 128GB. Since 128GB is vastly more than the amount supported by chipsets or available as DDR2 modules there will not be any overlap and the installed memory will not be reduced.
A 64 bit OS has a drawback though. All applications need more RAM since all their addresses, variables, etc. are twice as long. Based on that a computer that had just enough memory for its applications with 32 bit, will not have enough memory for 64 bit applications.
Depending on the amount of installed devices, a computer with physically installed 4GB and only 3.2 GB available to a 32 bit system, might have effectively more memory than a computer on 64 bit utilizing the full 4GB.

mtyermom said:

Now, for the dual channel question. If you're going to go for 3GB of memory, all you have to do is have 2x1GB for the first 2GB of memory, and 2x512mb for the 3rd GB. So you have 2 sticks of 1GB in dual channel mode, and 2 sticks of 512MB in dual channel mode, for a total of 3GB all in dual channel.

A solid statement, but given the current memory prices, i would suggest going for another pair of 1GB sticks. While a little of them may be wasted, they will still run in dual channel. Upgrading to a 64 system is not necessary as the benefits are mostly cosmetic in nature.

My opinion:
If you can get the upgrade to 64bit cheaply then i would suggest doing it, otherwise save the money. 64 bit might be the future but 32 bit will still be around for a long time.

March 11, 2008 3:21:48 AM

Also one other thing, some ram, regardless if you get the same brand, manufacturer, etc. will not let you mix and match diffrent ram sizes. Sometimes they just dont want to mix and match for whatever reason. Going with 3 or even 4 one gig sticks also stresses your front side bus more then if you get 2x 2gig sticks, and you will have to possibly kick up votages and other various things like mess with timings and such. Microsoft also "suggests" you keep your sticks matched as to not run into compatiblity issues. With the prices these days, id say go with 4 gigs, sure your going to loose half a gig, but with the prices its definetly a option, unless your a super cheap skate.
March 11, 2008 8:42:36 AM

Quote:
Now, for the dual channel question. If you're going to go for 3GB of memory, all you have to do is have 2x1GB for the first 2GB of memory, and 2x512mb for the 3rd GB. So you have 2 sticks of 1GB in dual channel mode, and 2 sticks of 512MB in dual channel mode, for a total of 3GB all in dual channel.

Quote:
A solid statement, but given the current memory prices, i would suggest going for another pair of 1GB sticks. While a little of them may be wasted, they will still run in dual channel. Upgrading to a 64 system is not necessary as the benefits are mostly cosmetic in nature.

Well the point is that my memory doesn't exist in 512-modules, so I need to have 4gb (or 3gb with 3 modules)

So actually you are all saying that going for 4gb isn't a problem, only that 3gb will be used.

don't forget I have got a 1gb-GC so I will loose a whole gig
March 11, 2008 10:20:31 AM

robertdv said:
Quote:
Now, for the dual channel question. If you're going to go for 3GB of memory, all you have to do is have 2x1GB for the first 2GB of memory, and 2x512mb for the 3rd GB. So you have 2 sticks of 1GB in dual channel mode, and 2 sticks of 512MB in dual channel mode, for a total of 3GB all in dual channel.

Quote:
A solid statement, but given the current memory prices, i would suggest going for another pair of 1GB sticks. While a little of them may be wasted, they will still run in dual channel. Upgrading to a 64 system is not necessary as the benefits are mostly cosmetic in nature.

Well the point is that my memory doesn't exist in 512-modules, so I need to have 4gb (or 3gb with 3 modules)

So actually you are all saying that going for 4gb isn't a problem, only that 3gb will be used.

don't forget I have got a 1gb-GC so I will loose a whole gig


512's are a joke these days even if you could get them.

go the full 4gb and who cares if you loose a gig or so, its there when you upgrade to an x64 operating system, and yes the video cards memory is apart of that pool, my 512mb video card pushed my ram down from 4096mb to 3008mb.

on an odd note when i left the remap feature in the bios on which limited me to 2gb the system still actually felt faster with twice the memory, even tho vista could only see (or use?) 2gb as before.......
March 11, 2008 10:21:28 AM

robertdv said:

So actually you are all saying that going for 4gb isn't a problem, only that 3gb will be used.

don't forget I have got a 1gb-GC so I will loose a whole gig


You will lose more than that GB then. Now that you have all the facts, you can make an educated decision yourself.

The options you have a pretty clear but the solutions all have their respective drawbacks. You could buy 2x2GB and move to a 64bit OS (with 6GB) or use just the new 2x2GB with your 32 bit OS(which would be less than 3GB). More sticks, as has been pointed out by blacksci, can be a hassle. No one can tell you what to do better than yourself. You know your budget, you know how much memory you need, you know how long it will last you and if it will be worth it.
March 11, 2008 1:01:54 PM

The difference between single and dual channel is tiny. I went from 4x512 to a single 2gb stick and my 3dmark06 score went down about 50 pts.
You could get a single 2gb stick now and add a second later, although they are soooo cheap, you could probably afford 2 now.
http://shop4.outpost.com/product/5 [...] IN_RSLT_PG

not for me, ddr3 you know...
March 11, 2008 1:04:37 PM

Thanks to you all, it was very informative!

I'm going for 2*1gb (which I have now), I'm goin to add one module of 2gb, so later I can add a module of 2gb again. (6gb in total) When the day arrives when I have 6gb I'm goin to a 64bit OS, for now I will stick with 32bit.
March 12, 2008 11:07:02 PM

robertdv said:
I'm using xp-pro, with 2gb DDR3.
But xp can only "see" up to 4gb max (32bit), I have got a 3870X2 with 1gb memory. So is it true that if I insert 4gb of memory only 3gb will be used (because of the 1gb of the Graphicscard)?

second question, if I use 3 modules of 1gb, will I have Dual-channel? or is 3gb non-dual-channel better the 2gb dual-channel anyway? (In other words, does the last module of memory destroys the dual-channel effect of the first 2 modules)



Adding the third will break your dual channel. It did for me when I added a 1GB module to a pair of 2x512MB modules. That said, as far as I know the dual channel barely makes a difference, and, correct me if I'm wrong, the difference can be from 3% to 8%. So it may be still worth it to go for single channel anyway.
March 19, 2008 9:08:48 AM

doomsdaydave11 said:
Adding the third will break your dual channel. It did for me when I added a 1GB module to a pair of 2x512MB modules. That said, as far as I know the dual channel barely makes a difference, and, correct me if I'm wrong, the difference can be from 3% to 8%. So it may be still worth it to go for single channel anyway.


Depends on the apps you run, but adding the extra stick will cut the memory bandwidth in half, with modern systems and performance it all adds up, that dual channel memory, that cpu with the extra cache, NCQ and SATA2 hdd's, that extra 200mhz cpu clock etc - each adds to create an overall fast system, if you have dual channel, USE IT.
March 19, 2008 9:19:10 AM

Agree with apache :)  And IMO if you can afford 3GB modules, I think you should be able to get 4 modules.

Ah, wait, you are on DDR3, that makes the price flying up to the ceiling ... Well, anyway, go with dual channels.
!