Portal: "Prelude", a Portal mod by Nicolas "Nyk018" Grevet, has received the RTX remaster treatment 15 years after its initial release. The mod includes full path racing, DLSS 3, and Nvidia Reflex support. It is also the first PC game to support RTX IO, Nvidia's implementation of a new standard aimed at reducing texture load times and file sizes.

Portal: Prelude RTX is available on Steam starting today; for RTX-branded GPUs, the minimum requirement appears to be RTX 2060, but more power will be needed to overdrive the path tracing.

The new release includes not only a technical overhaul, but also new voice acts and a new test chamber for raging, as well as new and improved mods.

The big point, however, is RTX IO support, which is the first game (mod) to support the new GPU decompression technology.

RTX IO is a way to move the work of decompressing game assets, or high-resolution textures, from the CPU to the GPU. This is done to reduce texture load times.

This cake is from Portal: take a look at the cake from "Portal: Prelude" shown in Nvidia's test video: without RTX IO, the cake's textures load completely in 3 minutes and 46 seconds.

With RTX IO enabled, the cake loads in 1:01 seconds.

RTX IO is Nvidia's way of implementing GDeflate on their GPUs; GDeflate is an open source data compression scheme, created by Nvidia and contributed elsewhere. But to understand why, one must examine why today's CPU-based decompression is not the ideal solution.

As AMD outlines in their GDC presentation slides (PDF), while playing a game, the CPU spends many cycles compiling shaders, decompressing game data, and initializing game objects. The decompression task actually consumes a lot of resources and system I/O bandwidth. For this reason, shifting the thorny task of decompression to the GPU can actually benefit the user in the game: with GPU decompression, the CPU is free to tackle other important tasks, avoiding the traditional bottlenecks.

"When applying traditional compression, where decompression is done on the CPU, the overall bottleneck is the CPU, resulting in lower throughput possible with uncompressed streaming," states Nvidia's technology blog. Not only does it "underutilize the system's available I/O resources, but it also takes CPU cycles away from other tasks that require CPU resources.

Removing the decompression phase from the CPU still allows game data to pass through the CPU and system memory, but the GPU can use its rich cores to speed up the decompression process.

You are probably not alone in your confusion as to how RTX IO combines with other GPU decompression technologies. Many companies are involved in implementing GDeflate and have their own spin on it. Basically, both Microsoft's DirectX 12 and Khronos' Vulkan API support GPU decompression.

Nvidia, Intel, and AMD all plan to support GPU decompression and GDeflate on their graphics cards through driver support and related technology. is.

Nvidia is pushing the technology under its own banner first, thanks to its RTX Remix program, which gives it the flexibility to work closely with developers on such projects. is: Rift Apart, which is expected to launch later this month with DirectStorage 1.2 support for GPU decompression. It will support GPU decompression via DirectStorage 1.2 and is expected to launch at the end of this month.

Nevertheless, to take full advantage of these new storage technologies, you will probably need an NVMe SSD. Even "Ratchet & Clank" works with conventional hard drives, so it is not a prerequisite, but the benefits will certainly be diminished with much slower storage technologies. If you haven't already upgraded to SSDs, now is certainly a good time to do so.