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Old 07-05-2011, 07:26 PM   #1
Offler
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Join Date: Nov 18 2009
Location: Bratislava
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X48 and 8gb RAM DDR3

So after only two weeks I have some info which might help to people with X48 and 8gb a bit, but I encountered one mystery.



These are my A-Data 1866+ XPG V2.0
CL 8-8-8-24
Voltage 1,55v-1,75v

Chips: Elpida Hyper MNH

CPU is Xeon X3360, board is DFI x48-t3rs.

According to elpida datasheets chips are manufactured for 1600Mhz CL8 at 1,5v. X48 is second Intel DDR3 chipset supporting up to 8gb of memory.



Crappy fat coolers were unable to fit into the board with all 4 sticks so I replaced them with Arctic Cooling RC (non pro).


4gb configuration:
CPU 1,3v
VTT: 1,265v
RAM 1.6-1,712v
Chipset: Stock - 1,265v

At 1333Mhz the chips were able to run on CL5 which is incredible for such frequency. At 1600 I was unable to set it to CL6. Such configuration was refused. Always on any settings. At all the chips run very well on 1600CL7 CR1.

8gb configuration:
CPU 1.3v
VTT: 1,136-1,210v
Ram: 1,712v
Chipset: 1,4v

At any tested frequency ram was unable to get under CAS8. No matter what. Despite of this no performance reduction (towards higher CAS and performance level) was measured by Linx or 3d Mark2011. Actually I have +100 points in 3dmark.

And to the mystery... With less memory the CPU VTT has to be set to higher values for stable performance. Previous configuration with OCZ 1600CL7 4gb was stone stable and passed 5000+ Linx tests at 1,265v at VTT.

When i used Elpida Hypers in 8gb is unable to get stable at this VTT voltage. I expected it would require more volts, but instead I had to lower it. A lot... So I set it to voltage I think its expected for CPU at this FSB frequency and start the tests again.

(1,21 volts on VTT reflects CPU/FSB overclocking by 20 percent)

at all I dont have any explanation why 8gb configuration requires less VTT volts as 4gb, even when i raised volts on NB core... Any ideas?
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Old 13-05-2011, 10:54 AM   #2
Offler
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So I have to read another parts of some Intel documentation.

Intel X48 memory hub with 8gb ram guarantees 1333Mhz at CL 8-8-8-x. And it seems there is no way around this, (at least not with double sided memory modules).

Since I am trying to run 8gb on 1600Mhz the high NB voltage (1,4v) and forced CR2 (since today testing) means possibility to run the memory on such frequency and amount, but the price is getting bit high...

Edit:

What do you think? Is 1,444v and 55 degrees too much for this chipset?

aircooled with Thermalright Heatpipe and noctua...

Last edited by Offler; 13-05-2011 at 11:17 AM.
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Old 31-05-2011, 08:15 AM   #3
Offler
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My recent tests of X48 with ramdrive shows something i find bit disturbing when it comes to Quad core configuration...

HD CrystalMark always shows CPU utilization 25 percent, and average read of 4500mb.

there are two possibilities:

1. Ramdrive based on software lowers the performance of memory.
2. Core 2 Quad has two separate L2 caches, and two separate chips of course.

Both chips are connected via single 775 socket. That could mean that its bandwidht will be halved - each half for one chip.

Earlier I have seen 3dmark tests of E8400 and the performance was much better as with Q9400 and similar quads.

L2 cache memory is fast as hell. even single chip can use up all the bandwidth which is provided. Only good thing is that cache is really large.
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