OT: IWill DK88, dual Opty with EIGHT dimms per cpu

  • Thread starter Thread starter Rob Stow
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Rob Stow

http://www.iwill.net/product_2.asp?p_id=102&sp=Y

Has anyone found something explaining how they manage to get 8
DIMMs per CPU ?

I was under the impression that the built-in memory controller
limited the AMD64 chips to 4 DIMMs and an external controller
(VIA an HT link) was necessary if you wanted to have RAM
configurations not supported by the internal controller.
However, I can find no sign of an external memory controller in
anything I have read so far about this motherboard.
 
Rob Stow said:
http://www.iwill.net/product_2.asp?p_id=102&sp=Y

Has anyone found something explaining how they manage to get 8
DIMMs per CPU ?

I was under the impression that the built-in memory controller
limited the AMD64 chips to 4 DIMMs and an external controller
(VIA an HT link) was necessary if you wanted to have RAM
configurations not supported by the internal controller.
However, I can find no sign of an external memory controller in
anything I have read so far about this motherboard.
Click to expand...

Socket 939 uses unregistered DIMMs, limited to two DIMMs per memory
channel IIRC

Socket 940 uses registered DIMMs, limitation is much higher due to
less mem bus loading. But adds to memory latency; nothing comes
free. ;-)
 
Is that 4 DIMM limit with registered or unregistered memory?

I saw the writeup about that board too, it's definitely an unusual
development.

Yousuf Khan
 
YKhan said:
Is that 4 DIMM limit with registered or unregistered memory?
Click to expand...

Registered ECC.
I saw the writeup about that board too, it's definitely an unusual
development.
Click to expand...

HP has 4P and 8P Opty boxes with 8 DIMMs per proc. Each CPU and
its DIMMs are on a separate daughter card. I've been wondering
the same things about those DIMM slots.
 
http://www.iwill.net/product_2.asp?p_id=102&sp=Y

Has anyone found something explaining how they manage to get 8
DIMMs per CPU ?
Click to expand...

From AMD's product brief from the AMD Opteron:

http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/23932.pdf

Under the memory controller it states:

"Supports up to 8 registered DIMMs"

I was under the impression that the built-in memory controller
limited the AMD64 chips to 4 DIMMs and an external controller
(VIA an HT link) was necessary if you wanted to have RAM
configurations not supported by the internal controller.
However, I can find no sign of an external memory controller in
anything I have read so far about this motherboard.
Click to expand...

The key word in the above specs is *registered*. The Athlon64 can
only support 4 unbuffered DIMMs per channel, but the Opteron uses
registered memory and can support twice as much.

FWIW this is hardly the first system to use 8 DIMMs per CPU. HP's
Proliant DL585 server also has 8 DIMMs per CPU. However that system
has some limitations as to what speed the memory can work at depending
on just how many DIMMs are installed. If you fill up all 8 DIMM
sockets you must run your memory at DDR266 speeds. I suspect that
IWill's solution will have a similar set of limitations.
 
Socket 939 uses unregistered DIMMs, limited to two DIMMs per memory
channel IIRC
Click to expand...

No really true - s939 CPUs have always supported up to 4 ranks per channel,
i.e. 2 DIMMs but you get into speed err, compromises (MHz and 1T vs. 2T
comamnd rate) above 2 ranks with previous CPUs. The Venice and San Diego
cores are supposed to mitigate this somewhat and can run up to the full
speed of 200MHz/DDR400 with 4 ranks but it's not clear what command rate
you can get there.
 
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