Athlon 64 - Max memory 4GB?

[Pat]

Hello all,

I'm planning to replace my 3 year old pentium system, and was looking at
some athlon 64 PCs as possible options. I'd like to get something that can
handle more that 4GB of memory, if not too expensive (I do FEA work
occasionally which can use LOTs of ram) which is why I was looking at the
Athlon. I assumed since it was 64bit cpu it could handle more than 4GB.
However, all of the athlon systems I looked at only supported 4GB (same as a
standard 32 bit system). Although I found some Opteron systems that could
handle more, they were quite a bit more expensive.

Being new to AMD processors (obviously) I was wondering if the 4GB limit was
due to how these particularly computers were designed (to reduce cost) or
how the Athlon 64 is designed? The later would surprise me though, as I
thought the main advantage of a 64 bit cpu was larger memory addressing.

Thanks for any clarification on this. Any PC suggestions are also very
welcomed.

Pat

 

[Brian]

Hello all,

I'm planning to replace my 3 year old pentium system, and was looking at
some athlon 64 PCs as possible options. I'd like to get something that can
handle more that 4GB of memory, if not too expensive (I do FEA work
occasionally which can use LOTs of ram) which is why I was looking at the
Athlon. I assumed since it was 64bit cpu it could handle more than 4GB.
However, all of the athlon systems I looked at only supported 4GB (same as a
standard 32 bit system). Although I found some Opteron systems that could
handle more, they were quite a bit more expensive.

Being new to AMD processors (obviously) I was wondering if the 4GB limit was
due to how these particularly computers were designed (to reduce cost) or
how the Athlon 64 is designed? The later would surprise me though, as I
thought the main advantage of a 64 bit cpu was larger memory addressing.

Thanks for any clarification on this. Any PC suggestions are also very
welcomed.

I think the addressing is 40 bits. So yeah, you should be able to
use much more than 4GB. But it's really academic as you're looking
at the problem from the wrong view.

OS, motherboard,and practical availability of parts will be bigger
obstacles.

I'd say 4GB will be a practical limit on PCs for a good long while.
It's way too early to plan those types of upgrades. Actually, in
general, it's a lousy time to plan on anything with PCs. So I'd say
buy what you need today without looking too far ahead.

 

[General Schvantzkoph]

Hello all,

I'm planning to replace my 3 year old pentium system, and was looking at
some athlon 64 PCs as possible options. I'd like to get something that can
handle more that 4GB of memory, if not too expensive (I do FEA work
occasionally which can use LOTs of ram) which is why I was looking at the
Athlon. I assumed since it was 64bit cpu it could handle more than 4GB.
However, all of the athlon systems I looked at only supported 4GB (same as a
standard 32 bit system). Although I found some Opteron systems that could
handle more, they were quite a bit more expensive.

Being new to AMD processors (obviously) I was wondering if the 4GB limit was
due to how these particularly computers were designed (to reduce cost) or
how the Athlon 64 is designed? The later would surprise me though, as I
thought the main advantage of a 64 bit cpu was larger memory addressing.

Thanks for any clarification on this. Any PC suggestions are also very
welcomed.

Pat

As a practical matter you can't put more then 4G on the Athlon 64, if you
need more than 4G you'll have to buy an Opteron system. The problem is
that the largest unbuffered DIMM is only 1G, until they start to offer 2G
unbuffered DIMMs there is no way to put more than 4G on an A64. The
Opteron uses registered DIMMs which are available in 2G. 2G registered DDR
DIMMs are pricey, as are Opterons, but you can put 8G on a single Opteron
and of you get a dual Opteron board you can put 16G in the system.

 

[Pat]

I think the addressing is 40 bits. So yeah, you should be able to
use much more than 4GB. But it's really academic as you're looking
at the problem from the wrong view.

OS, motherboard,and practical availability of parts will be bigger
obstacles.

I'd say 4GB will be a practical limit on PCs for a good long while.
It's way too early to plan those types of upgrades. Actually, in
general, it's a lousy time to plan on anything with PCs. So I'd say
buy what you need today without looking too far ahead.

Thanks for the reply. It's not an immediate need so may just hold off a
while until prices drop a little more on Opteron systems (which will
probably happen next year once Intel starts coming out with their new crop
of dual-core processors).

Pat

 

[Pat]

On Thu, 29 Sep 2005

As a practical matter you can't put more then 4G on the Athlon 64, if you
need more than 4G you'll have to buy an Opteron system. The problem is
that the largest unbuffered DIMM is only 1G, until they start to offer 2G
unbuffered DIMMs there is no way to put more than 4G on an A64. The
Opteron uses registered DIMMs which are available in 2G. 2G registered DDR
DIMMs are pricey, as are Opterons, but you can put 8G on a single Opteron
and of you get a dual Opteron board you can put 16G in the system.

Thanks for the info on this.

I noticed that many of the Opteron systems had 8 memory slots for
accommodating larger memory configurations. So can this not be done with
Athlons? I assume not, since I haven't seen it.

Do you have any idea when 2GB, unbuffered DIMMs might be out?

Thanks again.

Pat

 

[General Schvantzkoph]

On Thu, 29 Sep 2005


Thanks for the info on this.

I noticed that many of the Opteron systems had 8 memory slots for
accommodating larger memory configurations. So can this not be done with
Athlons? I assume not, since I haven't seen it.

Do you have any idea when 2GB, unbuffered DIMMs might be out?

Thanks again.

Pat

The 8 slots on Opteron systems is because there are two processors, there
are four slots per processor. It's not possible to put more than four
DIMMs on an Athlon 64 because they use unbuffered DIMMs which severely
load the memory bus. If you look at the specs for A64 motherboards you'll
notice that the maximum bus speed for two double sided DIMMs on the same
bus is 167MHz DDR not 200MHz which tells you that the load from two DIMMs
is pushing the limit.

As for 2G unbuffered DIMMs, they are technically possible now, 1Gb DDR
RAMs have been defined and I think they are shipping, so you could build a
double sided 2G DDR DIMM. However the DIMM manufacturers must be waiting
for the price to drop before putting them on unbuffered DIMMs. Unbuffered
DIMMs are aimed at consumer systems which are price sensitive. Registered
DIMMs are used in servers which are less price sensitive which is why 2G
registered DIMMs are already available. My guess is that we'll see 2G
unbuffered DIMMs next year. What I don't know if the current BIOSs will
support them, I'm pretty sure the memory controller on the Athlon 64 can
support 2G DIMMs.

 

[Derek Baker]

The 8 slots on Opteron systems is because there are two processors, there
are four slots per processor. It's not possible to put more than four
DIMMs on an Athlon 64 because they use unbuffered DIMMs which severely
load the memory bus. If you look at the specs for A64 motherboards you'll
notice that the maximum bus speed for two double sided DIMMs on the same
bus is 167MHz DDR not 200MHz which tells you that the load from two DIMMs
is pushing the limit.

My MSI K8N Neo Platinum is running two double-sided DIMMs at 200MHz. The
good memory support was the main reason I went for it.

 

[General Schvantzkoph]

My MSI K8N Neo Platinum is running two double-sided DIMMs at 200MHz. The
good memory support was the main reason I went for it.

You got lucky, if you read the spec it says 167MHz for two double sided
DIMMs on the same bus. My MSI K8N Neo4 with an X2 4400+ is unstable with
two pairs of 1G OCZ DDR 3200 DIMMs at 200MHz. When I substituted a pair of
Crucial 512M DDR 3200 DIMMs I couldn't even boot. It might be possible to
use DDR 4000 DIMMs and get away with it, my OCZ DIMMs almost worked i.e.
the system would stay up for 12 hours or so but I'd occasionally get a
lost event which would leave a process in an unkillable state.

 

[Wes Newell]

I noticed that many of the Opteron systems had 8 memory slots for
accommodating larger memory configurations. So can this not be done with
Athlons? I assume not, since I haven't seen it.

Do you have any idea when 2GB, unbuffered DIMMs might be out?

AMD says the memory controller of the A64 will support memory technology
up to 4GB, so that means with 4 slots it support 16GB. 2BG DDR unbuffered
has been out for a while now. Not sure about 4GB. And these have been
validvalidated by AMD. Cost?

http://www.samsung.com/Products/Sem.../UnbufferedDIMM/M368L5623MTN/M368L5623MTN.htm

 

[General Schvantzkoph]

AMD says the memory controller of the A64 will support memory technology
up to 4GB, so that means with 4 slots it support 16GB. 2BG DDR unbuffered
has been out for a while now. Not sure about 4GB. And these have been
validvalidated by AMD. Cost?

http://www.samsung.com/Products/Sem.../UnbufferedDIMM/M368L5623MTN/M368L5623MTN.htm

Are you sure these are shipping? I plugged the part number into Pricewatch
and Froogle and got nothing.

 

[Scott Lurndal]

Hello all,

I'm planning to replace my 3 year old pentium system, and was looking at
some athlon 64 PCs as possible options. I'd like to get something that can
handle more that 4GB of memory, if not too expensive (I do FEA work
occasionally which can use LOTs of ram) which is why I was looking at the
Athlon. I assumed since it was 64bit cpu it could handle more than 4GB.
However, all of the athlon systems I looked at only supported 4GB (same as a
standard 32 bit system). Although I found some Opteron systems that could
handle more, they were quite a bit more expensive.

Electrically the northbridge memory controller on the Athlon64
(and the opteron) only supports four DIMM slots. With 1GB DIMMS,
4GB is the max the motherboard will support.

Opteron motherboards with two sockets (and two processors) will
support twice that. When 2GB DIMM's are available at a reasonable
price, they should allow the memory size to double (given appropriate
BIOS sizing support).

scott

 

[Derek Baker]

You got lucky,

Or not. The manual for my board says DDR400 for two double-sised DIMMS.

 

[Wes Newell]

Are you sure these are shipping? I plugged the part number into Pricewatch
and Froogle and got nothing.

Product status at the bottom of the page says they are in mass production,
and I know I saw them validated by AMD at least a year ago. Samsung
announced 2gb ddr in 2002, and 4gb ddr in 2003. I have no idea where to
buy them. I only have 512M now with no plans for any more. Suggest you
contact Samsung or a Samsung semiconductor rep if you really want them.

 

[Nymshift Time Again]

Or not. The manual for my board says DDR400 for two double-sised
DIMMS.

I have 4G of pc3200 running at 200 on my Abit 4400+

 

[Frank de Groot]

Although I found some Opteron systems that could
handle more, they were quite a bit more expensive.

Be advised that even the most expensive dual-Opteron boards that alledgedly
support 24 GB (MSI Master-3 etc.) do NOT support more than 4 GB unless you
use SLOWER RAM or 2 GB sticks. I have the Master-3 and I can't use more than
4 GB when I use 1 GB PC3200 DIMMs. 2 GB DIMMs might work to yield 8 GB but
only a single vendor is supported. I did not know this so I assumed I would
be able to use 12 GB by simply buying more 1 GB DIMMs. not so..