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Documentation about the Vampire hardware

Cant Disable Fpu Gold 2.9

Stephen A.

Posts 21
24 May 2018 20:58


vcontrol fp 0 reboots the system, but the fpu is still active

tried with x11 and x12 (i didn't try x10)

vcontrol fp 0 works fine with gold 2.8


Roy Gillotti

Posts 393
24 May 2018 22:20


Have you tried doing this in the startup-sequence? I noticed some features don't like being toggled while running, but work find on boot.
 


Martin Soerensen

Posts 231
25 May 2018 09:01


I think all settings go back to defaults after a reboot, so they have to be set in SS. Perhaps the reboot happens because you have started some software which uses the FPU and then crashes the system when it disappears suddenly?


Stephen A.

Posts 21
26 May 2018 01:51


vcontrol fp 0 will reboot the machine <- this is normal

what is not normal is that the fpu is still enabled after the reboot instead of being disabled

vcontrol fp 0 works normally in 2.8 and earlier, but seems broken in 2.9

putting vcontrol fp 0 in the startup sequence would cause the machine to reboot forever.

its not an issue with workbench either... i tried it on a clean install of wb 3.1

can anyone else verify if they are able to disable the fpu on core 2.9?

and... just in case it is helpful to someone else, i wrote 2 tiny programs:

checkfpu -> returns 1 if an fpu is detected and 0 if there is no fpu detected

disablefpu -> will check if an fpu is detected and if it is will run "vcontrol fp 0" (which will reboot the system). if no fpu is detected the program doesn't do anything.

disablefpu will only work if vcontrol is somewhere in your path (ie,  Workbench:C)

i wrote disablefpu so that i could put it in my startup sequence so that i could disable the vampire fpu by default (because of some fpu inaccuracies).

warning: if you put disablefpu in your startup sequence, the system will reboot forever with gold 2.9

it works well on 2.8 and earlier.

source included: EXTERNAL LINK


Vojin Vidanovic

Posts 1676
26 May 2018 01:54


Excuse me for asking, but why would one disable FPU now when its hardware implemented? It made sense when FPU emulation did integer hit, but not since 2.9

Note: I see now because of FPU not being 100% accurate. Hope it will be bugfixed.


Roy Gillotti

Posts 393
26 May 2018 03:52


Stephen A. wrote:

  putting vcontrol fp 0 in the startup sequence would cause the machine to reboot forever.

Did you actually try it, or just assume it would reboot forever? you can always boot without Startup-Sequence if such a thing did happen.


Stephen A.

Posts 21
26 May 2018 03:58


Roy Gillotti wrote:

  Did you actually try it, or just assume it would reboot forever? you can always boot without Startup-Sequence if such a thing did happen.

i actually tried it ;) it rebooted forever...


Mallagan Bellator

Posts 381
26 May 2018 15:33


Stephen A. wrote:

Roy Gillotti wrote:

  Did you actually try it, or just assume it would reboot forever? you can always boot without Startup-Sequence if such a thing did happen.
 

 
  i actually tried it ;) it rebooted forever...

Oh no! Youíre still sitting there, arenít you? Forever is such a long time, isnít it? xD lol
Jk, it sucks. But hey, you have an FPU!! ;)


Tomas Tkald

Posts 4
01 Apr 2020 14:06


Please, it is a way to "native" disable FPU with vcontrol and CORE GOLD 2.12?



Henryk Richter
(Apollo Team Member)
Posts 117
01 Apr 2020 18:32


Gold 2.12 always (re-)enables the FPU at cold boot. That step was done in order to support Kickstarts other than the default that ships with the Vampire core updates. One example is 3.1.4 which disables the FPU at cold boot once a CPU with certain 68060 features is detected. Another example is the recent 3.X by Cloanto.

It is possible to disable the FPU at runtime but the associated tool has not been released as of now due to very limited testing (and the law of unintended consequences in mind).

posts 10