Old pcs (Pre ATX)

[imported_goku]

Ok I noticed that a lot of PCs back in the day had these "turbo" buttons and I wonder what exactally do they do? I have tried it but some times it actually slows down the machine and the number dial gets scewy at times. Why dont they have them on PC's now? I asked some one this a long time ago and it was never really answered so I am hoping it could finally be answered, thanks.

 

[Elcs]

Originally posted by: goku2100
Ok I noticed that a lot of PCs back in the day had these "turbo" buttons and I wonder what exactally do they do? I have tried it but some times it actually slows down the machine and the number dial gets scewy at times. Why dont they have them on PC's now? I asked some one this a long time ago and it was never really answered so I am hoping it could finally be answered, thanks.

I believe the Turbo button was used to slow down the 'then high end machines' for DOS programs which would run too fast on the high end pc's of those days to be good/fun/whatever.

Thats what I was told.

 

[Spikesoldier]

the turbo button overclocked the FSB by 1MHz i believe.

when you ran on such a slow FSB with a multiplier of anywhere from 1 to 4 i think, you bet that 1-4 MHz was something pretty good back in the day of sub 100MHz CPU's.

2nd poster also has a point, i think it was also used for that function.

edit: also, the correct term for "pre-atx" machines is AT.

 

[imported_goku]

I know they were called AT but I didn't use AT because I was including ALL machines that were pre ATX era, so they could be customized as well.

Edit: Wait how can it Overclock and Underclock at the same time? I need some more clarification, I ask this because I have heard numerous reasons for them and each answer is different every time.

 

[thelordemperor]

My friend used to have a 386/40 Mhz (I think).

Turbo On was normal speed, and certain games wouldn't run properly. We'd play Darksun and everything happened in teh blink of an eye.

Turbo Off underclocked it to 20MHz (I think), at any rate it was much slower and we could see the animations happening.

 

[Davegod]

IIRC: some sftware was timed on the fsb, so newer cpu's with newer fsb would break the software. hit the turbo button and it would put it to the fsb for compatibility - perhaps adjusting the multiplier aswell, since the apps were based not on the overall speed of the cpu, but only the fsb.

its something like that anyway. possibly the button was used for overclocking later on, when it was becoming obvious the software that needed the slow-mode wasnt being used anymore, so they used the button for something else.

 

[htmlmasterdave]

afaik it wasn't used for overclocking, but with turbo in it was the full speed of the cpu, and without turbo it would go down to something like 8-16mhz on a 486 to make it compatible with slower programs

 

[imported_Kiwi]

Originally posted by: htmlmasterdave
afaik it wasn't used for overclocking, but with turbo in it was the full speed of the cpu, and without turbo it would go down to something like 8-16mhz on a 486 to make it compatible with slower programs

That's accurate as far as it goes. The timing problem didn't appear during the original lifetime of the IBM PC-AT machines. You didn't even find a "Slow Down" option on the very earliest of 386's.

The first such switches I can recall were on various Clones of the AT running 80286's at 16 MHz speeds, and the switch dropped their speed to the same as the original PC-AT's, only 6 MHz. Many 386's had the Turbo buttons. By the time 486's were affordable for use in "Basic PC's", the need for such speed control had mostly passed.

:beer:

 

[bendixG15]

Older cards, especially video cards, could not run at the top speed of the CPU.
So, if your cards couldn't keep up, you hit the turbo switch to take it out of turbo mode.

In todays termonolgy, the FSB was overclocked and if you cards could keep up, you took
it out of overclocking by hitting the turbo switch.
Nothing changes much.......