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Turbo Button history?

FishFinger said:
I suspect both ideas are equally right and that turbo buttons existed to solve "compatibility problems" with no more specific reason needed. Trade magazines took that to mean copy protection on business software since that's what they and their readers were familiar with, and other people took it to mean games. There doesn't need to be one exact reason that makes all others wrong.
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This. I can easily imagine an engineer hunched over a prototype motherboard thinking "If I speed things up I don't even know what out there could possibly break. But if I put in a speed switch, it will 100% match IBM's specs. Let the user choose and hope compatiblity gets sorted out later."

There were a few copy protections that rely on speed, but I'd sort of think that relying on exact speed would have been considered a big mistake after the IBM AT was introduced. Actually, wouldn't the IBM PCjr have throw things off a bit? Even non-"turbo" clones sometimes had odd timings, and TSR programs could sometimes throw things off a bit even on genuine IBMs.

Also, not all of the turbo 8088s I worked with had turbo buttons, but I found it darn handy when they did have buttons. The problem with keyboard switching is that some DOS programs mess with the keyboard and prevent that from working. I'd guess the keyboard method existed for "upgrade" boards going in to old non-turbo cases, new machines also using older non-turbo cases, and for vendors that either wanted to save a few cents omitting a button or offering both turbo/non-turbo variates without physical differentiation.

It actually seemed kind of odd that turbo buttons continued in the 286/386/486 eras, but there were still plenty of poorly written programs that ran too fast if they ran on a newer machine than what they were designed against.
 
My recollection about many Taiwanese turbo panels, is that the pushbutton switch was wired as SPDT, so you could have it either way.

On old Far East XT clones, the turbo action was keyed from bit in the 8255 that was formerly used on the 5150 for cassette control. So no buttons at all. As a matter of fact, if you've got the right XCO handy, you can install a "turbo" mode in a stock 5160 with very little effort (of course, the clock will run fast)--I suspect that's how turbo mode got started.
 
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Chuck(G) said:
My recollection about many Taiwanese turbo panels, is that the pushbutton switch was wired as SPDT, so you could have it either way.

On old Far East XT clones, the turbo action was keyed from bit in the 8255 that was formerly used on the 5150 for cassette control. So no buttons at all. As a matter of fact, if you've got the right XCO handy, you can install a "turbo" mode in a stock 5160 with very little effort (of course, the clock will run fast)--I suspect that's how turbo mode got started.
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Back in the day I wrote a program to soft switch the turbo mode, it worked on every XT clone I ever came across and for many years the AT class clones also worked. It seems that the unofficial and undocumented speed switch functionality was put into the 8255 emulation of the keyboard controller.

For anyone that might be curious port 61h d3 was the toggle, here is the code I pulled out of my old source code.
The reason to read the port and bit flip was to not mess up the settings in the other bits.
To set turbo mode...
IN AL,61H
OR AL,04H
OUT 61H,AL
Set Normal speed...
IN AL,61H
AND AL,FBH
OUT 61H,AL
Toggle it....
IN AL,61H
XOR AL,04H
OUT 61H,AL

If you are wondering I never ever came across it documented anywhere, most of the hidden hardware features I learned by disassembling utilities supplied with computers coming out of Asia. I became quite skilled at it due to the number of RTC programs I had to reverse engineer to add support for unknown cards to my clock program.
 
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Actually, it was pretty simple to figure out. The switch had to be done using existing latches present in the hardware and the 8255 port 61, bit 2 was the cassette motor control bit in the 5150. As the 5160 didn't have a cassette port, that bit was up for grabs. I think I wrote my first "toggle" program in 1986 for a generic non-turbo clone that I'd modified.

Early XT clones with turbo mode simply tied pin 13 of the 8284 clock generator to the appropriate 8255 pin and fed a 3*f XCO into pin 12. Easy, peasy. Of course, on these early mods, everything, including the 8254 counter ran at the faster speed. Later versions fed the 8254 with a constant frequency, so that the time-of-day didn't get messed up. You could also modify the BIOS routine that kept track of the time of day and add suitable correction.
 
Our first PC was a 286 clone, and it had a turbo button and a LED MHz display. Turbo on was 16Mhz and turbo off was 12Mhz. I was confused when I started seeing everyone claiming that turbo slows it down. Then after doing some research, 'turbo' implementations are all over the place.
 
Chuck(G) said:
My recollection about many Taiwanese turbo panels, is that the pushbutton switch was wired as SPDT, so you could have it either way.
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The first PCs I built myself were 286s and this was certainly true for them. I usually had it so the button was pushed in for turbo on, but it could easily have been reversed; it was just a preference.
 
carangil said:
Our first PC was a 286 clone, and it had a turbo button and a LED MHz display. Turbo on was 16Mhz and turbo off was 12Mhz. I was confused when I started seeing everyone claiming that turbo slows it down. Then after doing some research, 'turbo' implementations are all over the place.
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It depends on how you plug the switch into the board, its a double throw switch generally so you can turbo with the switch in or turbo with it out.
 
I never saw a turbo button up until extremely recently because I've always only been around name brand clones and not generic clones. This is something that I have noticed, turbo buttons seem to have been almost exclusively used on generic clones...
 
6885P5H said:
I never saw a turbo button up until extremely recently because I've always only been around name brand clones and not generic clones. This is something that I have noticed, turbo buttons seem to have been almost exclusively used on generic clones...
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My Gateway 4DX-33 has a turbo button and light:

523719384_1280x720.jpg
 
Interesting discussion. I had several 286+386 machines in the day with "turbo" modes and buttons. Maybe my XT clone had one too, come to think of it. Being in New Zealand, these would have all been East Asian clones of some type or the other. I always ran my machines with turbo enabled and never had any problems with software. From what I recall, non-turbo mode was there "just in case" some software couldn't handle the higher speed. Just what that software was was never clarified.

Tez
 
All turbo buttons that I saw (including on my own clone) came with a light which came on when you pressed the button, which corresponded to higher ("turbo") speed. I've never seen or heard about a "turbo" button that slows down the machine. That wouldn't have been called "turbo". These buttons came around the time when saab introduced "turbo" in family cars, and the term quickly became associated with "higher performance" in the general population, not just among sports car enthusiasts. So I can't imagine anyone adding a "turbo" button to slow down a computer. I don't believe it.
In any case, I never ran into any software that didn't work at the higher speed.
 
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Tor said:
I've never seen or heard about a "turbo" button that slows down the machine. That wouldn't have been called "turbo". These buttons came around the time when saab introduced "turbo" in family cars, and the term quickly became associated with "higher performance" in the general population, not just among sports car enthusiasts. So I can't imagine anyone adding a "turbo" button to slow down a computer. I don't believe it.
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There's some confusion here; I don't think it was ever claimed that pressing the Turbo button slowed down the computer. The original point made was that the computer ran fast by default (ie. with no turbo button hooked up), and the turbo button signal at the header told the motherboard to introduce wait states to slow down operation. So the turbo button was typically wired in reverse so that pressing it actually removed the signal which let the motherboard run in its default fast speed.

Disclaimer: I am not an electrical engineer.
 
Many "turbo" buttons were alternate-action, so the matter of "which way is up" is irrelevant. That's why an LED or display was used to indicate the state.
 
That's a more elegant construction of what I was trying to say. The salient point is that, with no button connected whatsoever, the board runs at full ("turbo") speed. Adding one gives the control, so I think that's why they were referred to as slowdown buttons by systems builders (by my recollection, at least).
 
tezza said:
From what I recall, non-turbo mode was there "just in case" some software couldn't handle the higher speed. Just what that software was was never clarified.
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Imagine an early card game where:
* When cards are dealt from the pack, it is done relatively slowly so that the player feels suspense as each card is dealt.
* The response time of other players (the computer) is such that it approximates the time that real players would respond in.
* The programmer timed things for a 4.77MHz 8088 (faster PCs hadn't been released yet).
* The user loves the look-and-feel of the game and does not want to buy a replacement (different look-and-feel).

Tor said:
So I can't imagine anyone adding a "turbo" button to slow down a computer.
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Some makers may have simply referred to the button as a "speed" button.
 
Trixter said:
The salient point is that, with no button connected whatsoever, the board runs at full ("turbo") speed.
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Not always. One motherboard example is at [here]. See page 5-6

But, per post #35, if the case maker used a SPDT type of switch, then the computer maker could choose the behaviour they want, 'turbo' = button out (my preference), or 'turbo' = button in.
 
I heard yet another theory on why turbo button was introduced: some early networking stuff failed to work at higher speeds.

BTW, in certain book I saw recommendation to turn off turbo when running commands like FORMAT, DISKCOPY, DISKCOMP...
And I had at least one machine where it was handled automagically (in BIOS?): even though the button was set to turbo, during diskette operations the system switched itself to de-turbo, it was clearly visible via the turbo LED.
 
My first gen Pentium seems to automatically slow down for older games. I've got games from 1985 that work fine on it. Go any earlier than that and nope.
 
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