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Instructions to Install and Use RyuJIT

Try RyuJIT -- Your code runs faster on X64 Windows

How to enable RyuJIT

Download and install RyuJIT now.

RyuJIT only works on 64-bit editions of Windows Vista and Windows Server 2008 and later.

After installation, there are two ways to turn on RyuJIT. If you just want to enable RyuJIT for one application, set an environment variable:

set COMPLUS_AltJit=*

If you want to enable RyuJIT for your entire machine, set the registry key:

Default (string) = "*"

Both registration methods cause the 64-bit CLR to use RyuJIT instead of JIT64. You can remove these settings at any time and you'll return to using the regular JIT64.

Known Gotchas

  1. No NGen Support. RyuJIT doesn’t change NGen on your system—we wanted to keep the CTP install clean
  2. No Edit & Continue. If you enable RyuJIT while writing code, you’ll find that Edit & Continue doesn’t work on 64-bit. One work around is disable RyuJIT while debugging.

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@Spacefish Spacefish commented May 27, 2015

Hello, i had RyuJIT CTP5 installed and activated machine wide. After updating to .NET 4.6 (via VS2015 RC installation), some of my .NET Applications crashed on startup.. Guess RyuJIT is incompatible with .NET 4.6? This is my bug report i mistakenly created against 4.6:
After i removed the global RyuJIT enable key in HKLM\SOFTWARE\Microsoft.NETFramework\AltJit everything is back to normal..

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