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Memory upgrade support: DDR3 Low Voltage ECC vs DDR3 1.5v Non-ECC (Dell T20/ Optiplex 9020/ Precision T1700)


I recently bought the Dell T20 Xeon version which came with a Hynix ECC Low Voltage 4GB module:HMT451U7BFR8A. (I included T1700 and 9020 in the title since all three systems share the same motherboard)

I recently upgraded the memory with a single 8GB 1.5v 1600 Non-ECC Crucial module (CT102464BA160B ). So I have one Crucial module in Slot 1 and one hynix 4gb stock ECC in another. And they are working fine, I ran the memory test without any issues. 

I read on the Hynix product page that his particular module supports backward compatibility with 1.5V and hence I'm assuming both the current ram modules are operating at 1.5v instead of 1.35v./

I read somewhere that if a system supports 32GB of Low voltage RAM, it can only support 16GB of 1.5v ram. Is this true?

I'm planning to add another 8GB non ecc 1.5v crucial module to make a total of 20GB. 

Will this config work? Are there any special power constraints that the motherboard's on-board power regulators have? Since this motherboard only gets as 12v supply and does rest of the conversions onboard. 

As for the power supply, I'm using an aftermarket 550watt unit. 

Replies (2)


This is odd, as the T20 shouldn't operate with Non-ECC dimms, as almost all Dell Poweredge servers require ECC. So the dimms you are using shouldn't be working. 

To answer your other questions;

"I read somewhere that if a system supports 32GB of Low voltage RAM, it can only support 16GB of 1.5v ram. Is this true? "

This isn't the case, as there is no capacity limitations caused by specific voltages being installed.

"Will this config work? "

With the memory channels being laid out as Channel A: memory sockets 1 and and Channel B: memory sockets 2 and 4. With 3 dimms installed, you cant match the channels. With the T20, to achieve dual-channel performance, the total memory in each channel must be the same. If the channels do not match or if the system has only one dimm installed, the system memory operates in single-channel mode or in dual channel asymmetrical mode. The system works normally in single-channel mode, but you lose the benefit of increased memory throughput. Dual-channel mode is always present when both memory channels are populated. However, for optimum dual-channel performance, the size of the modules must match.

.Let me know if this answers your questions.

Chris Hawk
Social Media and Communities Professional
Dell Technologies | Enterprise Support Services

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Hi Chris,

Thanks for the reply. The non-ecc works I think because the C226 chipset supports both ECC/non-ecc. If you look at the product specs page of Precision T1700, you'll see it has the exact same specs as the T20 and supports Non-ECC memory. Based on my reading I detemined that the T1700 and T20 share the same exact motherboard. (Unless of course Dell White-lists certain components for T20 over T1700, which doesnt seem to be the case so far).

So, if I add another 8gb module, the memory won't work in dual channel? (8 + 8 + 4) ? 

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