English Amiga Board

Go Back   English Amiga Board > Support > support.WinUAE

Thread Tools
Old 16 June 2016, 12:04   #1
Registered User

hexaae's Avatar
Join Date: Jul 2006
Location: Italy
Age: 42
Posts: 803
JIT checkboxes detail

Where can I read details about WinUAE JIT checkboxes?
In general I've found that setting everything ON and 'Indirect' mode some WHDLoad games do not quit unexpectedly anymore (I had problems in particular with Overkill AGA, Bubba'n'Stix, The Killing Game Show, with 060 emulation, variable results at every WinUAE release)... so I wondered what the following options do, technically speaking?

Hard flush ??
Constant jump ??
FPU support ??

No Flags ??

Direct/Indirect ??
hexaae is offline  
AdSense AdSense  
Old 16 June 2016, 12:29   #2
Registered User

ED-209's Avatar
Join Date: Mar 2012
Location: OCP
Age: 38
Posts: 1,094
There is some description of those options here.
I find things work best with all settings at default 99% of the time.
Some demos benefit from disabling JIT FPU.
As for WHDLoad, JIT should really be disabled, unless it is some CPU intensive game (eg Alien Breed 3D II), in which case just use 040/060 + default JIT.
ED-209 is offline  
Old 16 June 2016, 12:46   #3
Registered User

hexaae's Avatar
Join Date: Jul 2006
Location: Italy
Age: 42
Posts: 803
Thanks! Didn't know that link...


JIT - Just In Time
UAE has always been hampered by being somewhat lacking in CPU performance.
Undoubtedly, it was amazingly fast for what it did, but it never really was an alternative to a decked out, no expense spared Amiga. The Just In Time compiler should help change that.

UAE can now emulate the CPU at considerably more than 060 speeds. That should do for a while - although further speedups are still possible.

A description of what the settings will cause the JIT compiler to do:

Cache Size: The size (in kB) the JIT compiler uses to store pretranslated code. When this becomes full, or when the OS issues a flush icache instruction, this gets completely emptied, and then refilled during execution. Setting it to 0 will disable the JIT compiler.

Const Jump: If this enabled, unconditional branches will not end a block. Effectively, UAE-JIT compiles "through" them. Generally, that's a good idea, as it improves performance.
However, it makes soft cache flushing impossible for some blocks, so if you experience lots and lots of soft cache flushes (e.g. when using a Mac emulator), you might try "no" and see whether it does any better.

FPU Support
: If this is enabled, the JIT compiler will be used for the most commonly used FPU instructions. Unchecking this option will disable JIT-compiling for the FPU.

Force Settings: Will force the JIT compiler to work with the method the user chooses.

Direct, Indirect, After Picasso: These describe how aggressive to be when it comes to accessing Amiga memory. If you choose "Direct", the emulation will be very aggressive. If you choose "Indirect", the emulation will always use the slower but safe method. "AfterPic" uses the safe method until the first time a Picasso96 mode is switched on, and the aggressive method
from then on. Unless you are not using P96 graphics, there isn't much point setting this to "direct". During the startup, weird and wonderful things happen in the Amiga, and only having faith in the aggressive method once that difficult time is over is certainly a wise thing to do.

No Flags: Whether to optimize away flag generation when it isn't needed. There really shouldn't be any reason why you'd want to disable this option. If you find something that
works with "no" and doesn't with "yes", it most likely is a bug and you should report it.

Hard Flush: If this is unchecked, an OS induced icache flush doesn't actually empty the cache, but instead checksumming will be used to check whether blocks have to be discarded. You'll probably want to leave this at its default (otherwise lots of stuff, like the OS, gets translated over and over).

The JIT patch was developed by Bernd "Bernie" Meyer, this description is a slightly edited and very shortened version of his documentation.

About JIT, yes I keep it on for Workbench but usually disable it via a S:WHDLoad_startup script/tooltype when launching a WHDLoad game (using C:UAE-Configuration tool) except a few demanding games.

I think I'll keep:

Hard flush: ON
Constant jump: OFF
FPU support: ON

No Flags: ON

Direct/Indirect: Indirect

Last edited by hexaae; 16 June 2016 at 12:52.
hexaae is offline  
Old 16 June 2016, 13:26   #4
Registered User

hexaae's Avatar
Join Date: Jul 2006
Location: Italy
Age: 42
Posts: 803
I think http://www.vware.at/winuaehelp/ should be added in WinUAE About panel...
This will save Toni from answering many FAQ
hexaae is offline  
Old 16 June 2016, 13:40   #5
Amiga 500 User
Join Date: Jun 2013
Location: EU
Posts: 1,129
If you need a help file, this one seems fresher -> http://www.vware.at/projects/winuae/
amilo3438 is offline  
AdSense AdSense  

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools

Similar Threads
Thread Thread Starter Forum Replies Last Post
FS-UAE - Why it have no JIT? nexusle support.FS-UAE 19 13 May 2012 14:39
Death Mask WHDload - Where has the DETAIL MODE gone? viddi support.Games 10 29 April 2009 08:04
JIT error Thom87 support.WinUAE 6 05 October 2008 21:38
Another little detail -> Data Disk Another World HOL suggestions and feedback 0 26 August 2008 23:19
JIT Emulation Doozy support.WinUAE 2 17 January 2002 08:14

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

All times are GMT +2. The time now is 16:34.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Page generated in 0.16399 seconds with 11 queries