Can Conroe support 8Gb RAM and on what MB?

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mikek753

Senior member
Dec 21, 2005
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Hello,

Does Conroe have 64 bit memory bus? or just 32 bit with memory extender?
Can it use more then 4 Gb RAM like a 16 Gb in 64 bit mode?

What MB to use for that?
I think that there are 8 slots only, so to get 16 Gb it needs 8 by 2Gb RAM.

thanks.
 
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Lord Banshee

Golden Member
Sep 8, 2004
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If i am not mistaken is purely OS and motherboard that limits the Conroe and A64 or any CPU for the matter. CPUs are limited by the address bits which is usually the register size bit size ie 32-bit or 64-bit)

32-bit = 2^32 = 4GB
64-Bit = 2^64 ~ 18,000,000,000 GB (not sure what this would be called other than more than anyone in the next 10 years will ever use or afford)
 
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dexvx

Diamond Member
Feb 2, 2000
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Couple corrections:

Bus width has nothing to do with address size. Netburst bus width is already 64bits for the first Willamette to Conroe (64bits * 100Mhz * QDR = 3.2GB/sec for 400 FSB systems).

Second, physical memory address size is 40 bits for the x86-64 definition. It is limited by OS (Windows XP can only assign 2GB per thread) and motherboard. I don't think any consumer grade board can do 8GB. You'd have to go with workstation or server boards with Woodcrest chips.
 
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Lord Banshee

Golden Member
Sep 8, 2004
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Ahh, Didn't know how many bits the x86-64 used for address..

Thanks for clearing that up. so thats about 1TB.

Dexvx, do you know if that address bit size is a standard or is it just what AMD and Intel are using for the time being... well i guess they almost make the standard as they are the only key players in x86.
 
DeathReborn

DeathReborn

Platinum Member
Oct 11, 2005
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Originally posted by: Lord Banshee
Ahh, Didn't know how many bits the x86-64 used for address..

Thanks for clearing that up. so thats about 1TB.

Dexvx, do you know if that address bit size is a standard or is it just what AMD and Intel are using for the time being... well i guess they almost make the standard as they are the only key players in x86.
Click to expand...

I'm not 100% sure but I think that 18,000,000,000GB is 18 Exabytes.

As for the AMD64/EMT64 they are both not fully 64bit as far as Max Memory goes.

Originally EM64T hardware allowed access only to 2^36 bytes of memory, while AMD64 systems can handle up to 2^40 (planned expansion to 2^56) bytes. However, as of recent publications, EM64T now provides 2^40 bytes of memory access.
Click to expand...
 
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Bladen

Member
Aug 19, 2004
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Originally posted by: dexvx
Couple corrections:

Bus width has nothing to do with address size. Netburst bus width is already 64bits for the first Willamette to Conroe (64bits * 100Mhz * QDR = 3.2GB/sec for 400 FSB systems).

Second, physical memory address size is 40 bits for the x86-64 definition. It is limited by OS (Windows XP can only assign 2GB per thread) and motherboard. I don't think any consumer grade board can do 8GB. You'd have to go with workstation or server boards with Woodcrest chips.
Click to expand...

AFAIK most mobos that have 4 RAM slots and handle 64 bit processors have a max limit of 8GB of RAM.

Not just Conroe and AM2 systems...

 
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dexvx

Diamond Member
Feb 2, 2000
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Duvie

Elite Member
Feb 5, 2001
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Originally posted by: dexvx
Couple corrections:

Bus width has nothing to do with address size. Netburst bus width is already 64bits for the first Willamette to Conroe (64bits * 100Mhz * QDR = 3.2GB/sec for 400 FSB systems).

Second, physical memory address size is 40 bits for the x86-64 definition. It is limited by OS (Windows XP can only assign 2GB per thread) and motherboard. I don't think any consumer grade board can do 8GB. You'd have to go with workstation or server boards with Woodcrest chips.
Click to expand...

Dude....I linked the 975x (consumer grade) that specifically states

<<Intel 975X Express Chipset enables key performance-optimized capabilities such as support for multiple 2x8 graphics cards, Intel® Memory Pipeline Technology (Intel® MPT), 8GB memory addressability to enable 64-bit computing, and ECC memory support.>>

Plus the newest board by Gigabyte @ newegg...it is a 965p chipset...

http://www.newegg.com/Product/Product.asp?Item=N82E16813127235

 
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TanisHalfElven

Diamond Member
Jun 29, 2001
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Originally posted by: Lord Banshee
If i am not mistaken is purely OS and motherboard that limits the Conroe and A64 or any CPU for the matter. CPUs are limited by the address bits which is usually the register size bit size ie 32-bit or 64-bit)

32-bit = 2^32 = 4GB
64-Bit = 2^64 ~ 18,000,000,000 GB (not sure what this would be called other than more than anyone in the next 10 years will ever use or afford)
Click to expand...


who will ever need more than 656 kb ram. :p
don't forget the succeor to vista that will need that much just to boot up.
and don't mention battlefield 3.

sorry i just had to type this.
 
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Vee

Senior member
Jun 18, 2004
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You will typically first be memory limited by the program model (2GB for each process in Windows32), then OS ability to map to RAM (4GB for standard WindowsXP, you can use more memory but it will be in swap, not on physical RAM), then Mainboard (typically 2GB-8GB).
CPUs addressing limits is a different thing though they strongly influence OS and the program model. And that is why we should move to 64-bit as soon as possible.


Corrections to a number of above posts:

1: The current generation of AMD64 cpus is limited to addressing 1 TB physical RAM. This is just a limitation of early hardware implementation. Not a limitation in AMD86-64.


2: 32-bit X86 can per definition address 64GB.

But the largest linear space to map some of those 64GB to is only 4GB.

This affects a number of decisions regarding the design and function of OS and program model. In practice this means that the Windows32 program model only allows for using a 2GB space per process. This translates into ~1.5-1.7 GB max memory for a program.


3: AMD86-64 can per definition extend addressing to 4PB (1 PetaByte = 1024 TeraBytes)

But the linear space to map those 4PB is 16EB (1 ExaByte = 1024 Petabytes)

Note that in this case the space is larger than addressable memory! By magnitudes. In practice this means that 64-bit applications are unlimited in a wide range of cases where 32-bit applications today are confined and crippled.
You will however be limited by whatever limits Microsoft see fit to provide you with in their 64-bit OSes.
 
V

Vee

Senior member
Jun 18, 2004
689
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0
Originally posted by: Lord Banshee
Ahh, Didn't know how many bits the x86-64 used for address..

Thanks for clearing that up. so thats about 1TB.

Dexvx, do you know if that address bit size is a standard or is it just what AMD and Intel are using for the time being... well i guess they almost make the standard as they are the only key players in x86.
Click to expand...

No that's all wrong. The "address bit size" for AMD86-64 aka EM64T aka x86-64 is 64 bits in 64-bit mode. Nothing else! 64-bit code is required to generate 64-bit addresses.

But people do not seem to understand how this works. You're wrong to assume that this then gives the addressable memory. Addressable memory is ultimately 4 PB for AMD86-64. And currently available AMD64 processors are limited to 1 TB.

(BTW, 2^64 = 16 ExaByte)
(1 EB = 1024 PetaByte)
(1 PB = 1024 TeraByte)
(1 TB = 1024 GigaByte)
 
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