Update readme (#550)

Author: solidpixel

README.md

@@ -77,10 +77,16 @@ The x86-64 SSE2 builds will work on all x86-64 machines, but it is the slowest
 of the three. The other two require extended CPU instruction set support which
 is not universally available, but each step gains ~15% more performance.
 
-For Arm, if binaries are available, we provide:
+For Arm we provide, in order of increasing performance:
 
+* `astcenc-sve_256` - uses 256-bit SVE
+* `astcenc-sve_128` - uses 128-bit SVE
 * `astcenc-neon` - uses NEON
 
+Note: The Arm Scalable Vector Extensions (SVE) allow CPUs to have a variable
+vector length. The astcenc implementation is not written in a length-agnostic
+style and requires the binary to match the vector length on the host CPU.
+
 ## macOS
 
 For macOS devices we provide a single universal binary `astcenc`, which allows
@@ -235,10 +241,10 @@ or general mobile graphics development or technology please submit them on the
 
 - - -
 
-_Copyright © 2013-2024, Arm Limited and contributors. All rights reserved._
+_Copyright © 2013-2025, Arm Limited and contributors. All rights reserved._
 
 [1]: ./Docs/FormatOverview.md
-[2]: https://www.khronos.org/registry/DataFormat/specs/1.3/dataformat.1.3.html#ASTC
+[2]: https://www.khronos.org/registry/DataFormat/specs/1.4/dataformat.1.4.html#ASTC
 [3]: https://github.com/ARM-software/astc-encoder/releases
 [4]: https://community.arm.com/support-forums/f/graphics-gaming-and-vr-forum/
 [5]: https://developer.arm.com/documentation/102162/latest/?lang=en