A64 X2 Memory Controller

[Renegade87]

I'm sure someone has asked this before, but couldn't find it here...

As you all know there is an issue with the AMD Athlon64 single core memory controller that wrongly identifies installed memory capacity when 4 1GB DIMMs are installed (reports as 3+ GB apparently). It also will not run these doulble sided modules at their full rated DDR400 speeds, but rather reduces to DDR333.

I'm 99.9% sure this is also true wth the Athlon64 X2 CPU's as well, but just wanted verification without having to pour through AMD White Papers.

 

[JackPack]

Haven't of the first issue before. Are you referring to the PCI hole? Where 4 GB memory reports as 3.5 or so due to 32-bit XP?

The second issue has been resolved since E-step, which all X2 products are based on.

 

[zentech1]

Haven't of the first issue before. Are you referring to the PCI hole? Where 4 GB memory reports as 3.5 or so due to 32-bit XP?

The second issue has been resolved since E-step, which all X2 products are based on.

I have an X2 4400+ running on an Asus a8n sli premium. With 2 sticks, memory ran at the rated ddr400. However when I added 2 more for a total of 4 it dropped to ddr333. I checked the bios revisions and apparently an earlier bios version for this same board supports 4 sticks with ddr400, however asus dropped 4 sticks to ddr333 in the recent bios (1009). This is mentioned in the bios revisions. Not sure about the beta bios version. Maybe the E stepping is ok in general and its just the particular board I have that has a problem with 4 sticks at ddr400. Anyway, just thought I would throw that out there.

from asus site
A8N-SLI Premium Bios version 1009
1. Support new CPUs. Please refer to our website at: http://support.asus.com/cpusupport/cpusupport.aspx
2. Fix unstable under 400MHz-Single channel issue.
3. Modify DDR max speed from 400MHz to 333Hz when full loading .

 

[Renegade87]

I've seen this reported by a number of manufacturers (MSI, DFI) relating to the onboard A64 memory controller, but they aren't specific about which type CPU's are affected (A64, X2, FX) and lead me to believe it's all 3.

For instance, MSI reports this in relation to the K8N Diamond Plus: "Due to the South Bridge resource deployment, the system density will only be detected up to 3+ GB (not full 4GB) when each DIMM is installed with an 1GB memory module"

Southbridge? I thought only 1 chip was used in the NF4 SLI chipset? Anyways, anybody with an X2 running four 1GB DIMMs at DDR400?

 

[JackPack]

It's still the southbridge, although with Athlon 64, the southbridge now also has to take care of PCIe. Traditionally, the role of the northbridge is to handle the memory and AGP/PCIe. The memory controller has been moved on-die, and PCIe moved to the SB.

Anyway, I'm quite certain they're addressing the PCI hole. If you look at the P4 boards, specifically the 975X Platinum (download the manual), you'll see:

Due to the South Bridge resource deployment, the system density will only be detected up to 7+GB (not full 8GB) when each DIMM is installed with an 1GB memory module.

The K8N Diamond Plus replaces the above numbers with 3 and 4 GB because the motherboard can only handle 4 GB of RAM. But the idea is the same, they're talking about the PCI hole.