I'm building a PC with a Ryzen 7 9700X and a B850 motherboard, but I can only afford one 16GB DDR5 stick right now and the second one about a month later. I'm considering Patriot DDR5-6000 CL30. Is there a realistic risk that two separately purchased sticks won't work together or won't run at their advertised speed?
4 Answers
One important correction: a single DDR5 module isn’t already running in dual-channel mode. Dual-channel requires two modules installed in the motherboard’s recommended slots. Also, make sure the motherboard supports the capacity and memory configuration, and enable the appropriate memory profile in the BIOS after installing the second stick.
If the second stick might take many months or a year to buy, I’d lean toward waiting and purchasing a matched kit instead. Memory revisions can change over time even when the product name stays the same. For just one month, though, buying the same SKU is generally reasonable.
There’s no major practical risk with only a one-month gap. Most DDR5-6000 CL30 kits have some headroom, so identical modules will probably run together without trouble. If the system is unstable, you may need to lower the memory speed or adjust settings, and you should test the first stick while you still have a return window.
The safest option is always buying a matched 2-stick kit, since those modules are tested together. However, buying the exact same manufacturer, model, capacity, speed, and timings a month apart will usually work just fine. It just isn’t guaranteed to reach the rated speed because the sticks could come from different batches or use slightly different memory dies.

I need the PC now, so waiting for the full kit is difficult, but I’ll make sure to buy the exact same model and test the first stick right away.