Why is VRM on the motherboard, and how do I find which memory topology my motherboard has

[Rolf Rander]

Hi, I'm new here, so I'm sorry if this is an FAQ.

 

I just watched the entertaining and educational video on how motherboards work, and I have a couple of questions:

 

• I understand why VRM is important, but why is it on the motherboard, why not inside the power supply?
• for memory, T-topology is best for 2 memory module in each channel, daisychain is best with 1 mem in each channel (but then you really want just 1 slot per channel). But how do I figure out which topology my motherboard has? Specifically I want to know the topology of the Gigabyte TRX40 Aorus Wifi Pro that I already ordered, but I am really curious about the general case here. I can't find anything relating to "topology" in the manual.

 

 

[Electronics Wizardy]

5 minutes ago, Rolf Rander said:

I understand why VRM is important, but why is it on the motherboard, why not inside the power supply?

CPUs use like 1-1.5v and a very high current. You would need very thick cables to carry that much current for about a foot or so. That would also waste a lot of power and need huge connectors.

 

Also its much easier to have stable power when the vrms are next to the cpu so there is less capacitance and inductance in the wiring.

 

 

[Maurice Janssen]

its easy.

Many components in your pc need different voltages - as your fans are usually at their max at 12v this is the perfect point!

you basically run a 12v power supply & regulate the voltage for other components which need less, for example your cpu. also there are some feedback traces on your motherboard for the voltage regulation. basically would require a shit ton of cables for that. also having the regulation near to the cpu is better. 

I mean, have you looked at GPUs? They also have a big VRM section on them. 

[SupaKomputa]

9 minutes ago, Rolf Rander said:

but why is it on the motherboard, why not inside the power supply?

It's possible to have it in the PSU, but will make it unnecessarily complex, and different platform need different power regulation.

[mahyar]

about vrm:

because they output a very large amount of current anywhere between 35 to 150 amps

to output such a high amount of current you need THICK cables and i mean THICK 

AND psu would be wayyy larger for all that extra circuitry  

[Grabhanem]

44 minutes ago, Rolf Rander said:

Hi, I'm new here, so I'm sorry if this is an FAQ.

 

I just watched the entertaining and educational video on how motherboards work, and I have a couple of questions:

 

• I understand why VRM is important, but why is it on the motherboard, why not inside the power supply?
• for memory, T-topology is best for 2 memory module in each channel, daisychain is best with 1 mem in each channel (but then you really want just 1 slot per channel). But how do I figure out which topology my motherboard has? Specifically I want to know the topology of the Gigabyte TRX40 Aorus Wifi Pro that I already ordered, but I am really curious about the general case here. I can't find anything relating to "topology" in the manual.

 

 

Others have already explained it pretty well, but the loss over cables is basically related to the amount of current traveling through those cables, not the total amount of power. Transferring power at high voltage/low current for as much of the distance as possible makes the losses much lower. (This is also why power plants and mains stations run at very high voltage compared to household appliances.)

Most motherboards these days are daisy-chain, since very few people overclock multiple DIMMs per channel. According to Buildzoid, this board follows that trend:

 

Edit: I should mention that because so much more research has been dedicated to daisy-chain than T-topology, a lot of higher-end daisy-chain boards these days will beat T-topology even in 2-DIMM-per-channel configs.