Random access memory, or RAM, is a fast, temporary computer storage device that allows temporary tasks to be written to it and performed instantaneously. RAM is used for tasks you are actively working on and windows you have open on your computer. The two types of RAM are DRAM, which can hold more data, and SRAM, which is faster and more efficient but can’t store as much data. SRAM has better performance than DRAM, but DRAM is so much cheaper that it is the type used in nearly all desktop PCs. RAM runs on NAND flash, meaning that data can be stored without drawing power.
Beginning with capacity, I’ll come right out and say it: you probably need 16 gigabytes of RAM. No more, no less. A 16GB kit is able to run games at maximum quality settings, along with background tasks like Discord, Spotify, or Chrome. If you’re video editing or doing any kind of CAD, graphic design, photo editing, code compilation, or other professional work, you should get a 32GB kit.
The number of clock cycles, or cycles per second, a RAM kit can perform is measured in megahertz (MHz). The megahertz of your RAM kit correlates to how much data can be stored and transferred at one time. Slow RAM can produce stutters in games. For DDR4 memory, 3600 MHz is the sweet spot, and for DDR5, I’d recommend 5200 MHz.
CAS latency refers to the number of cycles it takes for the RAM to transport a piece of data from its module to the memory controller, to the CPU core complex. Thus, the lower the CAS latency, the better. It’s often best to get the RAM kit with the highest frequency and lowest CAS latency at a certain capacity. It’s also important to remember that DDR3 modules may have lower CAS latencies than DDR4, but DDR4 is still better because of vastly superior frequencies and technology. A RAM stick actually has four primary timings: CAS latency, RAS to CAS delay (the number of clock cycles needed to open the correct row of data), row precharge (the number of clock cycles needed to close an incorrect row), and row active time (the number of clock cycles needed to close an incorrect row and open the correct one). This is why you may see a kit labeled as 16-20-20-38 for its CAS latency, but in reality, only the 16 represents CAS latency (tCL), while the other three are tRCD, tRP, and tRAS. You may be inclined to get the cheapest CL16 RAM kit, but in reality, a 16-18-18-38 kit is better than a 16-20-20-38 kit, so be sure to look out for all of the primary timings. I would recommend a CAS latency of 16 for DDR4 for good price to performance, with 14 being premium.
RAM channels are the physical wires linking the RAM and the CPU and transmitting data. The number of channels on your motherboard indicates how many RAM sticks are supported. If there are four RAM slots, but your motherboard only supports dual-channel, you can still use four sticks, but in dual-channel. Each RAM stick has a 64-bit bus to the memory controller. For each channel, 64 bits can be read or written at once. With a quad-channel motherboard and CPU, you’d want to use four RAM sticks since 256 bits of capacity are available to you. If you put two sticks in a quad-channel board, you aren’t taking full advantage of the board’s performance. Inversely, if you get a motherboard that supports dual-channel, spending extra on four RAM sticks is pointless. Doubling or quadrupling the memory bandwidth is actually highly beneficial for performance. For a dual-channel setup, you’ll want to place one RAM stick in the first or second slot and the other in the third or fourth (one in each channel). Consult your motherboard manual for the optimal RAM configuration.
Everyone seems to talk about dual-rank memory, but not dual-bank memory. And others mix up the two. A memory rank is a block of data, stored in memory chips, that is 64 bits wide. Single-rank RAM is generally when a RAM stick only has memory chips on one side, while dual-rank indicates double the memory chips and therefore double the bandwidth of one stick (128 bits). Having a module with two or four ranks is like having two RAM sticks in one. However, this is a bad thing. Some web and game servers can only deal with a certain number of ranks at once, so it’s better to get four single-rank 4GB DIMMs than to get one 16GB single-rank stick. On the other hand, a memory bank is a device inside a RAM stick that increases RAM speed by decreasing the number or rows the memory controller has to open. It’s really complicated, but having more memory banks is better.
Double data rate (DDR) is a memory technology that transfers data twice as often as the antiquated synchronous dynamic random access memory (SDRAM) that it is based on. Double data rate means that the memory transfers data twice per clock cycle. It overtook SDR SDRAM in the 2000s thanks to its lower cost, lower voltage, and better efficiency. The modern RAM technologies, DDR4 and DDR5, are of course built on DDR. In AMD systems, the Infinity Fabric Clock (FCLK) connects the CPU core complex to the CPU memory controller. The FCLK frequency should always be set to half of your RAM’s rated speed. If you have 3600 MHz RAM, set your FCLK to 1800 in the BIOS for maximum system stability (since your DDR RAM is technically running at half its rated speed). It’s important to note that Infinity Fabric is affected by silicon lottery, so some memory controllers can’t push the FCLK past 2000 or even 1800 MHz. As such, past 3733 MHz, AMD automatically sets your FCLK to a 1:2 ratio, instead of 1:1. This allows for RAM speeds over 4000MHz, but it increases latency. Over on team blue, all 11th and 12th Gen CPUs have the same technology with the same general performance. But in BIOS setups for Intel boards, FCLK is called gears for the CPU integrated memory controller (IMC). Chips older than Rocket Lake that aren’t “X” series use Intel’s “ring bus,” or two ring buses connected by Intel’s Mesh topology. While the Infinity Fabric speed is directly linked to RAM speeds, the ring bus is not. Thus, the ring bus sees smaller performance gains from higher frequencies because increasing frequency does not lead to faster communication between CPU core complexes (which isn’t what Intel calls them). I’m not sure why Intel only supported up to 2933 or 3200 MHz for so long, but I know that the chips didn’t benefit from higher frequencies as much because the memory controller was separate from the processing cores. Luckily, now both AMD and Intel support super fast RAM, so the days of the ring bus are behind us.
T topology is when traces for each channel of RAM are the same length. Daisy chaining is when traces go to the first slot, then continue to each subsequent slot. If all four slots are used, speeds may be slower with daisy chaining, but speeds would be faster with two sticks. The reason slots two and four are generally ideal for dual-channel is because the traces end at the proper slots, so they don’t have to be reflected back to the CPU and cause increased latency. Check if your motherboard has T topology or daisy chaining, then decide whether you should get two or four sticks. If it has T topology, you should take advantage of four sticks. If it has daisy chaining, two sticks is the way to go.
The main question on everyone's mind right now is whether to upgrade to DDR5 memory. DDR5 sticks can hold more capacity due to larger capacity memory chips. Believe it or not, due to die stacking and having double the memory banks, DDR5 tops out at 2 terabytes per module (but average users can’t buy sticks that large). Early DDR5 modules can only reach 32GB as of now anyway. DDR5 is much faster, with most kits being at least 4800 MHz. DDR5 has 288 pins just like DDR4, but the notch has moved, so DDR5 does not fit in DDR4 slots. DDR5’s increased bandwidth and burst length, as well as decreased voltage, bring improved efficiency over DDR4. In TechSpot’s benchmark analysis, DDR5 only offered 2% on average gains in games across all resolutions with the 12900K, but the margin was above 10% in some titles. DDR5 seems like an obvious choice, but 32GB of DDR5-4800 CL38 starts at $270, while 32GB of DDR4-3600 CL16 sets you back $170. The DDR5 kit is obviously faster, but factor in the cost of a new motherboard and the choice becomes clear. If you are building your first PC now, consider DDR5 and Alder Lake. But seeing as AMD doesn’t even support DDR5 yet, I would not upgrade if you already have DDR4. Wait for prices to come down in a year or so.
In terms of RAM, you should pretty much always get standard modules. If you have CPU cooler clearance issues, get RAM with shorter heights, like Corsair’s Vengeance series. But some kits go even further. Very low profile (VLP) memory is made for industrial and business applications, not the consumer market. But it’s important to note that some green-PCB, no heat spreader kits of VLP memory can achieve consumer level speeds like 3200 MHz. If you need VLP RAM, you know you need VLP RAM.
Now it’s time for some concrete kit recommendations if you don’t want to research too much. If you are on a budget, consider the G.Skill Ripjaws V 16GB (2x8GB) DDR4-3200 CL16 kit for $64. It’s a 16-18-18-38 kit from a reputable brand for under $70, so it’s a good value. If you have more to spend but still want to be reasonable and get a good bargain, you could spring for the $87 G.Skill Ripjaws V 16GB (2x8GB) DDR4-3600 CL16 kit. The kit is the same as the previous one but with a higher frequency and different timings besides the CAS latency. Many kits are 16-19-19-36 in this range, not 16-18-18-38. If you have more to spend, check out the Kingston Fury Beast 32GB (2x16GB) DDR5-5200 CL40 kit for $270. Generally reputable brands include Corsair, G.Skill, Team Group, Kingston/HyperX, Crucial, Patriot, Gigabyte/AORUS, Thermaltake, Silicon Power, and ADATA/XPG. For now, I would avoid new brands like OLOy, v-Color, Vaseky, and Festtive. With that said, happy RAMming! Wait, that sounds wrong.
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