[Info] Why does DRAM performance tank if you don't use dual-channel?

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Let's assume we're doing 'dawn delivery' from a Coupang logistics center to an apartment complex called 'Femco Apartments.' How should we build the roads?

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Unless you're an idiot, you can immediately figure out that building a straight road is the way to go.

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But then, the demand for dawn delivery from the residents spiked, so they built another logistics center. What would be the most rational way to build the road then?

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Obviously, connecting it with another straight line would be the most optimized method. (Dual-channel)

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If you connect the roads in a roundabout way like that, deliveries will still happen, but you'll get massive traffic jams and low efficiency. (Single-channel)

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That's why motherboard manufacturers also recommend plugging in two DRAM sticks into different channels to set up a dual-channel configuration. There's no reason not to build a straight road and instead hook it onto another existing road. Basically, if you plug two DRAM sticks into the same channel, it becomes single-channel with lower bandwidth; if you plug them into different channels, it's dual-channel with higher bandwidth. Now, let's say the demand for dawn delivery grows endlessly, so now there are 4 logistics centers. But oh no, due to resident complaints, the local government says only two roads can lead into the apartment entrance. How should the roads be laid out then?

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You keep the two, but the other two have to be 'biting the bullet' and connected to the nearest existing roads (Full-bank). There's an issue with DDR5 performance dropping when all slots are filled (full-bank), and in actual DRAM, when the load increases like that, the voltage gets distributed, leading to poor signal quality and performance drops. Previous DRAM generations were slower, so it wasn't a huge deal, but current DDR5 is high-speed and mass-production stabilization is relatively low, so issues pop up. To use the road analogy... there are too many unnecessary roads, causing traffic jams and actually slowing down delivery speeds. Back in the day, there was no 'dawn delivery,' so you could just drive slowly and deliver fine, but now that dawn delivery exists, cars are in a rush and problems keep exploding.

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Recently, a post went up on D-Gall saying performance inevitably drops if you don't use dual-channel, so you definitely should. Some comments were like, 'Huh? Other benchmarks say there's not much difference,' and there's an occasional debate on other tech sites about whether you can actually feel the difference or not. To get straight to the point, there is definitely a performance difference. However, in our typical PC environment, there are many cases where you might not feel it. This is because PCs usually run multiple programs, data sharing between them is frequent, and data access can be significantly reduced through the CPU cache, lowering the required bandwidth. On the other hand, there are many cases of random data access, where capacity contributes more to performance than bandwidth. Therefore, on a PC, having more DRAM capacity feels like a bigger upgrade, while the bandwidth difference is harder to notice. Conversely, for programs like games that access and process massive amounts of data at once, DRAM bandwidth is crucial and can affect performance. This is especially true for games that rely more on the CPU than the GPU. Of course, if the capacity is the same, there's no reason to lower the bandwidth. So, if you have two sticks of DRAM, I absolutely recommend a dual-channel setup. Conclusion: 1. More RAM capacity is always better. 2. If you have two or more sticks, you lose nothing by going dual-channel.