Urgent Memory Question

OK got all my parts for my new build.
Heres my Question...I'm sure I read somewhere that THIS MOBO has a default memory voltage of 1.8volts

The G-Skill MEMORY I have states it needs 2.0-2.1 volts.
The Question I have is ......will I have a problem booting into the bios to change it???............I don't think I will but just wanna make sure,so I don't run into any probs
THANKS

Sometimes you will have issues. Most of the time it will boot ok, it may be underclocked a little bit, but normally it will boot ok. Do you have any other ddr2? If for some reason you run into issues you can boot with different ram and change the voltages, and proceed to change it out.

There are a lot of kits that require a voltage around that g skill and most of them still allow for booting at a lower voltage.

Especially with that ram, odds are it will boot at ddr2 800 at like 1.8 volts, and then you will just have to change some settings..

l know when l built my pc with the ocz plats they stated 2.1volts needed and the board manual stated that the default output was 1.5 but it booted as the bios detected it and changed it automatically

If you do have a problem....it will boot with one stick...boot with the one change options as needed in BIOS and then install other stick.

Don't worry, Papa, you won't have any issues.

First off, I agree with both SWK and BBALL. Both of them are correct. And here's why.

I guess it is pretty much irrelevant to introduce the concept of SPD tables but a little bit of technicality is required in order to understand the entire concept. SPD stands for Serial Presence Detect and, basically, it is an EEPROM that is located right on the memory module and it supplies vital information to the motherboard. Usually it has 256 bytes but 128 variants are also possible. This chip is pre-programmed by the manufacturer and no memory module is and nor will be produced without the SPD chip. The JEDEC has specified the General Standards and each memory module must meet their requirements in order ot conform with the standards. The data that is located on the SPD looks like a table, thus, its name "SPD table." This table is accessed by the motherboard's SMBus (which is a variant of I²C).

Now that we have understood what exactly is the SPD - let's check out the standards in more detail. From byte 1 up to 72 the table must be filled (contain the manufacturer-specified information). The leftover (until 255) are optional and they are hold the following: 72 = location/code; 73-90 = part number; 91-98 = manufacturing data, revision code, serial number; 99-127 = manufacturer's specific data; 128-255 = open for customer use. Needless to say the data located prior to the byte 72 are crucial. Sure, we all know that the CAS latencies and other timings are also located in this table. That's right - but other than those, dozens of other specifications are also located within. I'm going to attach those table-requirements from Micron (being in conform with the JEDEC norms).


Pay extra attention to the first segment of the table. What can you see at byte number 8? Yes, the Vdd of the DIMM.

Voltage Interface Level of this assembly
This refers to the power supply voltage Vdd of the DIMM. Standard DDR2 SDRAM module would be SSTL 1.8V
1.8V DDR2: 05h Recommended Default

This is how its specified in the JEDEC standards. Therefore, if the module really requires 2.0-2.1v and by this I mean that it is engineered that it won't work below 2.0-2.1v then on this byte the appropiate value can be found for those voltages and the BIOS is going to automatically identity and set them prior the POST process. So that by the time your system boots up the required VDIMM is supplied. However, these cases are pretty rare since the standard requires a default of 1.8v (and a minimum of 1.6v) for each and every DDR2 modules. Nevertheless, the thing is that almost always the modules can run fine and work alright on even lower voltages (~1.6v +/- 5% fluctuating) but they must specify a recommended voltage. It's nothing but a recommendation - those 2.0-2.1v ones. It's not a limitation or absolute requirement.

Additionally, these days the memory chips are created using a newer technology (thus, more efficienct requiring less power) that does not require those kinds of exact voltages on a constant basis. This means that, yes, those G-Skill sticks will boot up no problems on 1.8v, and heck, I'd bet that the system would POST even on 1.5v if for whatever reason the motherboard would feed them with only that much. Sure, it won't be stable, at least definitely not Prime95/Orthos-stable on 1.5v. But who knows?

In your case the manufacturer, G-Skill, states that in order to get the most out of the memory sticks you are going to need 2.0-2.1v. This does not mean that it's the minimum, it is just the guaranteed amount of voltages. And on which should the sticks not work stable (or not perform accordingly) then a RMA process could be started because it's a faulty/defective one. Furthermore, each DDR(2) stick must conform with the JEDEC standard requirements [link: here]. In the case of DDR2s the voltage starts from 1.7v and can go up to 3.6v.

Right after as your system will POST you can enter BIOS and set 2.0v-2.1v - but surely later on you will go beyond these because overclocking is on the horizon, methinks. So yes, this is the way you thought and that's how it's going to work. I mean, 99% of the times so we can take that for granted. Anyway, like I explained earlier, chances are that you won't need to manually set the voltages because 2.0-2.1v is going to be automatically detected and set if it is that much required.

All in all — no worries.

Reference and Further Reading:

TN-04-42 - MEMORY MODULE SERIAL PRESENCE-DETECT by Micron — here [pages 12 and 13].

4.1.2 – SERIAL PRESENCE DETECT STANDARD, General Standard - JEDEC Standard No. 21–C — here.

PS: Thanks Papa for giving me this opportunity to write and post something technical - that's why I've emphasized on the bytes in order to point out which contains what exactly. Unfortunately, it's the first time I did in 2008. I miss those days when we were talking about computer and micrprocessor architecture, low-level memory management, cache hierarchy, BIOS modding, altering the PCI configuration registers, and so forth. Oh well...

Thanks all ......I'll have to rep BBALL/SWK later......When I cycle