Help with turbo button speeds on 486

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Help with turbo button speeds on 486

Postby GabrielKnight123 » 2018-5-20 @ 15:16

Hi all, I have an i486DX2 66 CPU in a case with a turbo button when its on it displays 199 and when off its 25 this is from a case I acquired before I had the CPU and Mobo, I have seen the slow down that shows me the turbo button is working and I will have to get around to changing the display but first I need to figure out what speed and number to set the display at as Im finding it misleading. I used a program called CHKCPU with the results below:

Turbo ON
Internal CPU Speed = 67MHz
Clock Multiplier = 2.0
Bus Clock Speed = 33.5MHz
Current CPU Mode = I have tried both Real and Virtual
Internal (L1) Cache = enabled in write-through mode

Turbo OFF
Internal CPU Speed = 61.4MHz
Clock Multiplier = 2.0
Bus Clock Speed = 30.7MHz
Current CPU Mode = I have tried both Real and Virtual
Internal (L1) Cache = enabled in write-through mode

So as you can see turning the turbo off does not have much of an effect but I have also tried a program called Syschk V 2.46 and with option number 9 ie speed, the CPU Speed stays the same at 67MHz but the Throughput Speed is (turbo ON) 176.45MHz and (turbo OFF) 37.49, is this the speed of the motherboard cache? The CPU its self is running at 66MHz and all the jumpers are set on the motherboard right, should I just set the turbo off to 33MHz or is this wrong?
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Re: Help with turbo button speeds on 486

Postby BonesK » 2018-5-21 @ 02:32

On the 386DX-40 I'm currently putting together, there were some markings on the board explaining on of the jumpers. It said "CLOSE AT CLK=CLK 1/4, OPEN AT CLK=CLK 1/5". I took that to mean that since my jumper was open, my speed would be 1/5th of the 40MHz max speed of my processor. Perhaps yours has a similar jumper setting somewhere?
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Re: Help with turbo button speeds on 486

Postby firage » 2018-5-21 @ 02:39

The difference won't show up there. You should use a performance benchmark to estimate the impact: viewtopic.php?f=46&t=37844
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