How to check compatibility when building a computer<br>Confirm your motherboard supports the amount of ram you bought. Some older motherboards don't support more than 8 or 16 gb of ram. Check the type of ram that you need.
Motherboards made years ago only needed to support 8 or 16 gb of ram. 
The text only says "Some older motherboards don't support more than 8 or 16 gb of ram." It doesn't say why or whether that was sufficient. The model must have inferred it.