Uses for the Useless Buttons

On your PC Case

A Compilation by Bob van der Poel

A little while ago I posted the following message on the internet:

I just repackaged my PC into a nice tower case which came with RESET and TURBO buttons. The TURBO button is nice since when I press it the speed LCD changes from 120 to 188. The RESET does nada since I really never have a need to reset running Linux. So, the 64K question: Has anyone any nifty uses for these two switches besides there decorative value. Seems such a shame to waste them!

Here are some of the responses...if you have other ideas please send them to me and I'll add the to this list.

The Replies

How about using the TURBO button to toggle between two volumes for the PC speaker? Just put a resistor inline with the speaker and have the switch defeat it.

Ingo Wilken

The RESET-button is still useful as Reset under Linux. Netscape once locked up everything, and without it I would have to power down the machine. The TURBO-switch is quite nice to dis/enable the beeper :) I currently use it to switch one of my CDROMs from SCSI ID 4 to 6.

Michael C. Vergallen

You can use one of the switches to enable or disable the speaker so it will not beep.

Luca Di Taranto

I have plugged the turbo switch on some pins of my Mb to select the speed of my Pentium 133 (normal) to 166 (overclocked). Remember that you must turn off your machine before pressing the switch to change the speed of your CPU!

Malcolm Chan Chiang Yoeng

I'd thought of this, but was worried that it was too easy to accidentally toggle the switch while the system was running... Just as a matter of curiosity, any idea what would happen if you did change the clock speed while running? I mean, these CPU's use SRAM internally anyway, so dynamically changing the clock speed shouldn't be a problem, should it? What about the motherboard?

Hauke Theiler

I connected the Turbo-switch to the jumper on my motherboard that determines the CPU-Speed (seriously). So I can occasionaly drive my AMD K5-90 at 100 MHz. Since this could rise problems for some programs, I am glad to be able to switch back to the "original" 90 MHz (when powered off of course).

Peter Ahearn

I realise you want to keep the current function of your TURBO switch, but here's another use for it which is still related to its original purpose: USe the TURBO switch to activate/deactive prosessor overclocking. My friend did this and it works great...

David LeDeaux

— Just as a matter of curiosity, any idea what would happen if you did change the clock speed while running? I mean, these CPU's use SRAM internally anyway, so dynamically changing the clock speed shouldn't be a problem, should it? What about the motherboard?

I actually had a friend of mine do that. As far as I know, he never turned off the system before switching it. He was also working on a way to wire in a potentiometer to control CPU speed. (He's majoring in EE, so I assume he knows what he's doing grin

Kenneth R. Crudup

There's always the power switch - I take it you missed the "Linux on 24hrs?" thread. :-). Nothing's worse for electronic equipement than the shock of power-on.

M. H.

i'm not sure how u can do it but i've connected it to a pin on my mother board that toggles between Normal and Suspend modes since my MB supports APM which i guess most MB's and BIOSes supports it in these days .when i want to be away from my computer for a long time i press that switche and my screen blanks and the HDD stops spinning , i thinks also that the CPU slows down (or something similar).

Hannu Lammi

How about wiring it (RESET) to the serial port? You could read it with powerd (used to listen to UPS's power failure signals). It could be used to reboot or shutdown the computer.

Tilman Bohn

—And no one even mentioned neat ideas for the LCD display.

Well, you could use it to display the line status &c. of an internal modem or ISDN card. You'd have to hook it up to a port though, unless there's a way to directly program it, preferably in user-space. I think there have been some projects to get something like this working on de.alt.comm.isdn4linux a while ago...
Something similar could be achieved by just using the keyboard LEDs though, and probably much easier.

— Just thinking about it myself, would it be possible to have the LCD display the current processor load or some other neat system statistic?

If you do the hardware part mentioned above first, that would be another easy task.

Geoff Winkless

I once saw a machine that used the led display on the front of the machine to show some idea of the current track that was being accessed on the disk/hard disk...

Craig F Aoki

I wired it up to lock the keyboard on my server so i don't accidently hit keys or what not when I'm not on the server's console. Beat looking around for those damn keyboard lock keys and keeps people puzzled for a long time as to what the heck is wrong with the keyboard.

Borislav Deianov

I was playing with svgalib and many times it would lock up my keyboard so that I can't even shut down properly. So I wrote a small program that will execute a tight loop, say once a minute, and if the speed drops more than 20% it will shut down the system. So whenever my keyboard locks up I just press the turbo button and wait a bit. (On my 486 the turbo button does change the speed, not sure what happens on modern machines).

Florian Kolbe

I use the turbo switch to enable/disable termination on my scsi adapter which is usually the last device in the scsi chain. But when I connect an external scsi device, I disable termination on my adapter using the turbo switch.

Jason White

I wired my green power LED to the "traffic" LED and the amber turbo LED to the collision LED on my ethernet card. I have also wired the amber LED to show PCI IDE disk activity and used the original red LED to show SCSI bus activity in a system that had both IDE and SCSI drives.

How about uses for the keybord lock? Well, I wired my keyboard lock in series with the reset button so I could enable/disable the reset button.

Ron Arts

I use the TURBO switch to set my SCSI disk to Read-Only. Most effective on a firewall machine, to prevent tampering with your executables/configuration!

Nathan Stewart

This probably falls under stupid tricks, rather than useful ideas, but most of the speed LED's are jumpered - to drive it intelligently (like displaying CPU usage or system load) would be a fun project. (Fun project meaning impractical, twice as expensive and three times as much work as what you anticipated.) Instead, I tinkered with mine until I got it to make letters or patterns. (It currently say "Oh")

If you use the Turbo switch to disable the speaker, you can set the LED to say "On"/"Sh" or "On"/Of". As an indicator of speaker status.


You can put the Turbo-Switch on your SCSI Controller to enable/disable it's termination, so you'll be able to use external connected devices without opening your case. That's what i call portability (-;

Nils Rennebarth

We have an ASUS 200 (=NCR53c810 SCSI Controller) board in most of our Linux PC's.

The internal termination is enabled/disabled by a jumper. It need to be enabled if you do have internal SCSI devices only. It needs to be disabled to connect external SCSI devices like a tape etc. We use the Turbo Switch for this. In many cases the Turbo LED is connected directly to the switch, so it serves as an indication of the switch status.

Christian Treczoks

I used the TURBO button to mute the loudspeaker, and the KEYLOCK to enable/disable the TURBO button (i.e. the machine can only be resetted if the key is in the right position. As the keylock is normally locked, nobody can reset the machine without notice (Powercycling will be reported by the UPS as an anomaly)).

Future enhancements will include a seperate control computer (single-chip), which checks & controls the power flow of the machine:

  1. pressing the power-button in "off"-state starts the machine.
  2. pressing the power-button in "on"-state requests a shutdown.
  3. shutting down the machine switches power off. The control computer will also get a LCD for status information, and four function keys.
Matthias Bruestle

I wanted to interchange the SCSI-IDs of my harddisk and my MO, so that I can boot from both. Because my case has no reset button I installed one and than I discovered that HD and MO have these ultraminimicrojumpers to select the ID for which I had no connector. So now I can switch from "Magic" to "More Magic" and back with this switch.

Nic Roets

My pentium has a display like this

     _   _ 
  | |_| |_|
  | |_| |_|

so I encoded "liN" if the turbo is in, and "uS" if the turbo is off. Almost "LINUX !".

Charles Puffer

I have considered:

Maybe a contest should be run for the best working project (each person could enter plans and code under the GPL)

Martin Chisholm

The reset switch is occassionally useful, (if I reboot in games mode (a.k.a. WinDOS), my CD-ROM won't work unless I also use the reset switch. However, my reset switch sticks out, and I hit it one by accident (which is 2 times too many).

So I switched the keylock and the reset switch. I need the key to reset the computer. I've never accidentally reset it since.

And the turbo switch? How about a garage door opener....

Lucian Fratila

Well, another thing that can be done with the TURBO led (not the switch) is to connect it to some pins on the network card so that it is blinking when the network connection is up (ok, I know that most of the new network adapters do have such a led, but it's on the back of the computer so it's quite difficult to turn the server, look at the led etc. when your connection has dropped down).

Btw, I did this and it works fine.

Gyula Matics

I use the TURBO button to turn on some extra fans. I need those fans in the summer but they are rather noisy so i prefer to turn them off for the night. (i sleep in the same room where my computer is)

As for the RESET button: I plan to install an 5x10cm LCD panel to the front of two 3.5" drive bays to display system statistics. The RESET button will be used to advance to the next display function.

My previous case had a key lock too. I used that to turn on/off the speaker.

David C. Jenner

I enjoyed your page of what to do with the front panel switches. I was thinking exactly that just recently after upgrading to a mother board that does not do turbo (the way they used to). Some good ideas there.

I had the idea of putting a small speaker internally in the case that would hook up to the sound card, and using the turbo switch to turn it off/on (and maybe route it to an external connection when off). That way I wouldn't have to drag speakers around with the machine, which is luggable and travels with me.

I run Win95 on the same machine, so I need to keep the reset switch!

Voss Net

your list is quite interesting. As someone mentioned noone would use the speed display I think I have found something interesting for it. Have a look at wouldn't it be possible to hook the LEDs of the speed display to the serial port as described and use the program to display the load of the machine. And if the serial port does not have enough lines, the parallell port would be ok ?

I sent the following reply...any hackers ready to build this?

I grabbed the file and read it. I'm not a hardware expert (not an expert on anything really), but I think that for this idea to work you'd need a 7 segment LED driver chip . Also, I hate to think that I would sacrifice a port just for this...there are so few ports already. Mind you, if someone built a card to do this... bvdp.

Andreas Buschmann US/EC4 60/1F/110

I have an Alpha AXPpci and I have build a connector, so that I can boot the Console either from serial ROM or from Floppy.

Devin Reade

My turbo button isn't doing anything and the LED shows the usual clock speed. However, I've used the keylock for the hardware reset since I still wanted this feature but didn't want it easily activated. (Say, by a passing child.)

As for the reset button, I have an "external" modem mounted in one of the 5.25" drive bays. While this keeps the desktop cleaner, it makes it a pain when the modem (for some reason) locks up. The reset butten therefore power cycles the modem.

Ulrich Diez

I use the TURBO-button to toggle between the PC-Speaker in the cover of the PC and the PC-speaker-connector of the soundcard. I enjoy this "feature" when using old programs which still send their sound-outputs to the speaker (e. g. old DOS- or Schneider-PC-games ).

This list was prepared from public messages on the Internet in and around July/1997 and updated later after the initial publishing on my web page. If you have more/different suggestions please mail them to me and I'll include them in yet a future update of this page.

Neither I, my (deceased) wonder dog "Tora", my family, or any of the contributors to this document will take any responsibility for anything which happens if you do anything contained in this document (does that cover it all?)!

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Web Design--Bob van der Poel
This page "button-uses.html" was last modified on Thu May 12 18:42:42 2016