Over the past several years, The Tech Buyer's Guru has published several articles the effects of RAM and VRAM on game performance. In fact, or very first Gamer's Bench article explored the effects of VRAM overclocking, and our most recent Gamer's Bench RAM article looked at the effects of DDR4 RAM speed and quantity on gaming. But there are always more questions to be answered in the collective mind of PC enthusiasts around the world, and TBG is here to bring you those answers! And so we're here today to explore how system RAM and video card VRAM interact during real-world gaming situations. In particular, we were curious whether having more VRAM would lead to lower or higher system RAM requirements. We've often seen cited the recommendation for having twice as much system RAM as VRAM, and that was easy enough when video cards had 512MB or 1GB of VRAM.
We never put much stock in this suggestion; in fact we'd call it the tech equivalent of "an old wives' tale." And in the era of 6GB, 8GB, and even 12GB video cards, running a system with twice that amount of system RAM can get really expensive, really fast. But we know a lot of readers still believe failing to stick to this rule of thumb can bring powerful systems to their knees. In fact, we once had a reader challenge us regarding our Supreme Dream Machine Buyer's Guide, circa late-2015, when we recommended builders go with dual GeForce GTX Titan X 12GB video cards and 16GB of DDR4-3000 system RAM. Wouldn't this system fail to run games, our reader asked? Of course we knew it would work, but that got us thinking that the lack of accurate information on the Internet regarding this issue was bound to be confusing to more than a handful of PC enthusiasts.
To test as many scenarios as possible, we used a total of five video cards, three using an AMD Radeon GPU and two using an Nvidia GeForce GPU, ranging in VRAM quantity from 2GB to 8GB. Here are the cards we used:
- Sapphire Radeon R9 270X 2GB
- Sapphire Radeon R9 290 4GB
- EVGA GeForce GTX 980 4GB
- EVGA GeForce GTX 980 Ti 6GB
- XFX Radeon R9 390X 8GB
With regard to RAM, we chose the two most common configurations, 2x4GB and 2x8GB, using the following two kits during our testing:
The rest of our benchmarking platform's specs were as follows:
- CPU: Intel Core i7-6700K (overclocked to 4.4GHz)
- Motherboard: Asus Z170-A (thanks to Newegg and Asus for providing this review sample)
- Solid-State Drive #1: Samsung 850 Evo M.2 500GB
- Solid-State Drive #2: Crucial MX200 1TB
- Power Supply: EVGA Supernova GS 850W
- Case: Phanteks Evolv ATX
- CPU Cooler: Noctua NH-U14S (thanks to Noctua for providing this review sample)
- Operating System: Windows 10
We ran all tests at a resolution of 2560 x 1440 using maximum settings, except where specified, and all five of our video cards were set to reference speeds. We used a 1440p resolution in order to really push our VRAM, as the more typical 1080p resolution uses far less VRAM.
We'll be providing results for three games, as follows:
- The Witcher 3 - representing a low VRAM usage scenario (1GB-2GB)
- Battlefield 4 - representing a moderate VRAM usage scenario (2GB-3GB)
- Rise of the Tomb Raider - representing a high VRAM usage scenario (over 4GB)
We previously found in our DX12 benchmarking of Rise of the Tomb Raider that it exhibited some very unusual memory usage patterns. We ran it in the DX11 mode for this article, to ensure that any bugs still in the DX12 didn't distort our results. The other two games also ran in DX11 mode (Mantle was not used in BF4).
We ran a very lean system for each benchmark, keeping open only the applications required to run the games and collect our data. That meant Steam or EA's Origin to run our games, along with MSI Afterburner for data reporting. To make sure that our benchmarking PC really was using system RAM rather than virtual RAM, we manually set our virtual memory amount to 1GB. Why eliminate the virtual memory pagefile all together? Well, for two reasons, actually: Windows error reporting doesn't work without a pagefile, and furthermore, many applications fail to run. As it turns out, one of games also needs a significant amount of virtual memory to run in some scenarios, as we found out the hard way!
Remember, this article is about comparing 2GB vs. 4GB vs. 6GB vs. 8GB of VRAM and how they impact system RAM usage, it's not an AMD vs. Nvidia showdown, nor is it a showdown between 2GB and 4GB cards. You can find such benchmarks elsewhere on the 'net... we're staying true to our goals here: a rigorous analysis of the oft-cited recommendation for running twice as much system RAM as VRAM.
Hopefully we've made clear how we performed our tests. There's lots of data to go through, and let's start off with The Witcher 3 results, shall we?