Dont use Turbo switch when powered?

Discussion about old PC hardware.

Dont use Turbo switch when powered?

Postby GabrielKnight123 » 2018-9-16 @ 16:04

I was reading through a motherboard manual for a GA-586HX that has a pentium 200MHz CPU and in the manual is this:

The TURBO switch on the panel is used for controlling the system speed.
Some program developed on XT should be executed with a low speed system,
so a high speed system needs the speed switching function to change its
running speed.
The mainboard uses 50 MHz speed method to implement TURBO switching
function. The TB on mainboard should be connected to the TURBO switch on
panel, and user can push in or pop out the TURBO switch to enable or disable
the turbo function of system.
Please don't use switch ON/OFF when power is ON.


So its saying dont use the turbo button when the pc is on but ... WHY? Ive been using the turbo on another pc and nothing noticeable happens like black smoke or sounds of electric arcing.
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Re: Dont use Turbo switch when powered?

Postby gdjacobs » 2018-9-16 @ 19:16

Is that motherboard MMX compatible? If so, I recommend switching to an MMX CPU due to extended slowdown options available under SETMUL. It may not get you down to 8088 performance levels, but 50Mhz FSB and SETMUL should give very good flexibility.

I'm guessing popping the turbo switch can potentially result in bus or RAM timings being violated as the bus clock changes. Also, I believe some internal registers used for properly handling timing will be thrown off when the bus clock flips.
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Re: Dont use Turbo switch when powered?

Postby GabrielKnight123 » 2018-9-16 @ 19:36

I dont know if the motherboard is compatible with MMX but the CPU I got with it is a Pentium 200MHz with MMX im happy I found a motherboard in the pentium class that has a turbo switch. Im going to try it anyway and press it a couple a times to see what happens my guess is nothing bad.
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Re: Dont use Turbo switch when powered?

Postby BinaryDemon » 2018-9-16 @ 20:36

I wonder if this is specific to this board or that's general advice for any turbo button. I used to have an Epson 8088 (10mhz) with a turbo button and I used to toggle it all the time while running just to see the difference of 4.77mhz vs 10mhz. Never seemed to hurt anything. :)
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Re: Dont use Turbo switch when powered?

Postby keropi » 2018-9-16 @ 20:46

^ That seems to be motherboard specific so don't worry :)
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Re: Dont use Turbo switch when powered?

Postby kaputnik » 2018-9-18 @ 02:25

GabrielKnight123 wrote:I was reading through a motherboard manual for a GA-586HX that has a pentium 200MHz CPU and in the manual is this:

The TURBO switch on the panel is used for controlling the system speed.
Some program developed on XT should be executed with a low speed system,
so a high speed system needs the speed switching function to change its
running speed.
The mainboard uses 50 MHz speed method to implement TURBO switching
function. The TB on mainboard should be connected to the TURBO switch on
panel, and user can push in or pop out the TURBO switch to enable or disable
the turbo function of system.
Please don't use switch ON/OFF when power is ON.


So its saying dont use the turbo button when the pc is on but ... WHY? Ive been using the turbo on another pc and nothing noticeable happens like black smoke or sounds of electric arcing.


Got one of those GA-586HX boards in my S7 rig too. Managed to press the turbo switch by mistake more than a few times, it's identical to the reset button, and sits right besides, and the board is still fully alive :) It seems to do nothing at all while the computer is running.

gdjacobs wrote:Is that motherboard MMX compatible? If so, I recommend switching to an MMX CPU due to extended slowdown options available under SETMUL. It may not get you down to 8088 performance levels, but 50Mhz FSB and SETMUL should give very good flexibility.


Yep, it is. With a simple mod you can also run a MMX233 chip at full speed in it, which to my knowledge is guaranteed to have unlocked multipliers. Wrote some about the mod here. And yes, it makes for a hell of a flexible machine :) Edit: OP, if your MMX chip does 200 MHz in your board, don't mind this, then it should work with a 233 MHz chip too without mods.

GabrielKnight123 wrote:I dont know if the motherboard is compatible with MMX but the CPU I got with it is a Pentium 200MHz with MMX im happy I found a motherboard in the pentium class that has a turbo switch. Im going to try it anyway and press it a couple a times to see what happens my guess is nothing bad.


Well, the turbo switch only slows down the machine marginally by setting the FSB speed to 50 MHz. It's not like the turbo buttons on 486s and earlier, which takes the system speed down to 8088 levels. It's not very useful, better results can be achieved with Setmul.
Last edited by kaputnik on 2018-9-18 @ 03:05, edited 2 times in total.
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Re: Dont use Turbo switch when powered?

Postby .legaCy » 2018-9-18 @ 03:02

I mean why even bother with a turbo switch on a S7 board?
With setmul and cache enable/disable you can get pretty a wide range of compatibility(of speed sensitive software).
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Re: Dont use Turbo switch when powered?

Postby gdjacobs » 2018-9-18 @ 17:50

Because SETMUL and L2 cache enable/disable only gets you to slow 386DX territory. That's not slow enough for titles which require 286/386SX16 speed.
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