
Turbo Button - tosh
https://en.wikipedia.org/wiki/Turbo_button
======
janci
Turning off the TURBO mode on my P1 133MHz box helped with misbehaving cdrom
drive that refused to read cds. My explanation at the time was slower reading
is more reliable.

Oh the disappoitment when I disassembled the case and noticed the turbo button
is not connected to anything except for led display showing Hi and Lo on
7-segments. It was just placebo effect.

~~~
kungtotte
It's not necessarily placebo: [http://catb.org/jargon/html/magic-
story.html](http://catb.org/jargon/html/magic-story.html)

~~~
jlebrech
that could the premise to a movie. a kid finds the magic button his
grandparent's basement and flips it.

------
corysama
I’ve heard from multiple sources that the original goal of the “turbo” button
was back-compat for a feature of the original 4.77Mhz PC that depended on
clock-rate: using an NTSC TV as a monitor. The original PC could have been
5Mhz, but 4.77 chosen instead so that the CGA graphics adapter could use the
bus clock to sync up with the NTSC signal without needing an addition clock
(saved a good 25 cents on the hardware that way!). When faster PCs came out,
they lost the TV display feature. But, if you really needed it, you could
clock down your fancy 6Mhz PC back to 4.77 to regain TV display capability.

“TV back compat mode” is long and boring, so the button was named “turbo” in a
brilliant marketing move. It became so popular that PCs added the ability to
arbitrarily clock down at the touch of a button long after it made sense to do
so.

------
ryan-allen
I was about 6 or 7 years old, and the home computer wasn't much of a thing
back then, and the 12 year old kid next door got a 386 DX, which was a huge
deal, and he kept it in his bedroom! Lucky guy.

Anyway, his Dad loaded it up with some DOS games, which I would go over and
watch him play. He would play Prince of Persia and let me watch. I would
occasionally ask him if I could have a go.

He said I could only play if the TURBO button was set to OFF. I asked why and
he said that it was to "save electricity". I would play PRINCE.EXE at a snails
pace until he kicked me off, me being the determined kid from a non-computer
owning household.

The upside is that their family had a cat (which was albino, deaf as a post,
and eccentric as heck). They wouldn't let the cat inside (maybe to save on
electricity) and the cat adopted us because we let it in. They moved and we
kept the cat.

------
vasac
How I played Tetris: 1\. start it while turbo is enabled

2\. wait for Tetris to adjust to the speed of 8Mhz 8086

3\. turn off turbo and play Tetris almost twice as slow - actually managed to
reach 32000+ a few times ;) (as it overflows on 32768 you had to stop playing
just before or else you won't end on the high score list)

------
JasonFruit
I kinda want one on my desktop machine now. There's a simple beauty to a
button that can slow your computer down if it's too fast for you. Maybe one on
my life too.

~~~
TomMarius
My i7-7700 with 32 GB RAM is already crawling when I want to use Facebook
Messenger, slowing it further down would be terrible...

~~~
bartread
Yeah: software turbo buttons have been a thing for a few years now. I find the
Microsoft Teams client works quite well in this regard, also.

------
NietTim
Aaaah our first PC. It had a Intel 80286, a display up front and a turbo
button. I pressed it once. My parents became very mad. Because the fans of the
PC spun up so much in turbo mode, they thought it would damage the computer.
Just like how pressing ctrl+alt+delete did damage to the computer

Sweet memories

Still wish I hadn't taken that computer apart (and never put back together) in
my never ending quest to quench my curiosity

~~~
danieldk
_Because the fans of the PC spun up so much in turbo mode,_

That's interesting, because 286s and 386s normally didn't even have heatsinks.
Did they wire the turbo button to the fan of the PSU?

IIRC, heatsinks were showing up on low-frequency 486s and heat sinks with fans
on 486s >= 50MHz. I think (but may misremember) that most 486 fans were also
always running at the same speed.

(Not contesting your statement, just wondering what weird beast your first PC
was ;).)

~~~
NietTim
They must have. The computer spend some months at a tech savy uncle when he
first acquired some pre release version of windows 95 but it was also bought
probably from a local store.

~~~
danieldk
Windows 95 did not run on a 286, the 286 was very limited in running real mode
(8086/88) applications concurrently in protected mode (it did not have the
virtual 8086 mode that the 386 had).

The minimum requirement of Windows 95 was an 80386, though it was unbearably
slow (tried to run it on an 386SX25 or 386DX40). It was usable on a 486 with
8GB of memory.

------
karmakaze
My first personally bought computer was a 386 with said turbo button. Other
crucial performance features were the sram cache and the ability to overclock
the isa bus from the standard 8mhz up to 11.

This was particularly important for running OS/2 1.3 with the svga vesa (non-
accelerated) driver that was produced by an intern at IBM. That software made
many lives including mine better on a daily basis.

A weird thing was how at 11MHz I could audibly hear large screen refreshes.
Never quite understood where that sound was from.

~~~
taneq
When I was a kid, we had a BBC Micro that would make audible little hissy
noises when writing to the screen. At the time I just assumed it was "the
sound of the computer thinking" but in hindsight there was probably some EMF
cross-talk between the analog sound lines and the bus to the video memory.
Maybe this was something similar?

Even when the carrier frequency is orders of magnitude too high to hear, there
are usually harmonics low enough to be audible.

~~~
karmakaze
That makes sense. In my case I didn't have a sound card, OS/2 didn't have the
best support for peripherals or gaming. Before 1.3 running on something other
than a PS/2 was pretty much unheard of.

------
markbnj
Haha memory lane. I remember walking into a little computer store with a good
friend years ago and seeing a 386 that displayed some really odd frequency on
the front panel led, like 53 Mhz or something at a time when 33 Mhz was the
fastest 386 you could buy. I asked the owner and he said "Landmark speed!"
(Landmark was a popular benching utility and he had programmed the led to
display the benchmark results when the turbo button was pressed).

~~~
interfixus
Programmed? The speed displays I remember were simply wired to show whatever.
I've seen turbo buttons swapping the display between '66' and '33'.

~~~
schoen
I'm guessing the store owner ran the benchmark once and then hard-coded the
benchmark result in the display.

------
alkonaut
It just appeared to me that there are now people in tech who never saw one of
these.

------
albertgoeswoof
> Disengaging turbo mode slows the system down to a state compatible with
> original 8086/8088 chips. On most systems, turbo mode was with the button
> pushed in, but since the button could often be wired either way, on some
> systems it was the opposite.

Now I have no idea if the PC I grew up with was running much slower than it
could have been.

~~~
glhaynes
Surely you tried it both ways!

~~~
mirkules
And if you never noticed either way then it doesn't matter!

------
k__
I was rather amused when I read about this years ago. As a child I always
asked myself "why should I not press this button?!"

~~~
tr352
Only the cleverest of people figured out they could run their PCs on turbo
full-time.

------
tr352
> In almost all cases the display wasn't a measure of the speed, but the two
> "fast" and "slow" display options were set by jumpers on the motherboard

Ah yes, I remember changing those jumpers to get that display show the correct
speed, after overclocking my "CyrixInstead" 486.

~~~
northwest65
Do you remember seeing jumpers on the motherboard for that? The only ones I
recall seeing were on the display in the case itself, like this this:
[http://www.minuszerodegrees.net/led_speed_display/LED%20disp...](http://www.minuszerodegrees.net/led_speed_display/LED%20display%20-%20DP-524.jpg)

~~~
tr352
Yes these jumpers resided on the display board.

------
AnssiH
> The turbo button was linked to a turbo LED or MHz display on the system
> case, although the indicated MHz was not always accurate.

On my 486 system the display said "486" with turbo on and "66" with turbo off,
which does not seem to make any sense.

~~~
ars
On mine there were jumpers and you could configure the 8 segment LEDs to show
any numbers you wanted.

~~~
classichasclass
That's how mine is too. When its original owner added an AMD 5x86, they
changed it to show "133" in turbo mode.

~~~
rzzzt
One case I saw was configured to display "Lo" and "Hi".

~~~
dfox
That is how I always configured the display jumpers on AT cases. It seemed
more cool than meaningless numbers

------
modzu
"...cpu frequency was used for timing"

reminds me how even today how seemingly hard it is to program a simple clock.
for example, the countdown in pubg...

~~~
ajross
The original IBM PC lacked an RTC, clones (as with everything else) had
occasional portability glitches with them, and this was a decade before the
TSC arrived. If you wanted a game to have a delay loop, you counted
instruction cycles. If you wanted those delays to be portable, you manually
detected the CPU and ran a pre-calibrated custom loop.

Yeah, that seems hard to me.

~~~
pjc50
The "correct" way to do this was the 1/18th sec timer interrupt, even when the
RTC worked it didn't have sub-second resolution.

[http://www.pldworld.com/_hdl/1/VHDL_courses/www.ee.duke.edu/...](http://www.pldworld.com/_hdl/1/VHDL_courses/www.ee.duke.edu/Research/VHDL_tutorial/webtracer/node13.html)

~~~
ajross
I thought the PIT was slaved to the bus clock on early systems and wasn't real
time, no? Might be wrong.

------
jmharvey
I didn't have a turbo button on my first PC (mid 1990s), but the BIOS menu had
a "deturbo" option. I had one game (some version of The Incredible Machine, or
possibly a knock-off) that could only really be played in deturbo mode. I
envied my friends who could easily switch between turbo and deturbo; I'd
usually have to wait several extra minutes for the system to start up any time
I wanted to play the game.

------
dang
Also
[https://news.ycombinator.com/item?id=17345227](https://news.ycombinator.com/item?id=17345227).

------
js2
This is such a PC solution. When the Apple IIGS came out, there was a software
control panel to adjust the speed:

[http://apple2history.org/wp-content/uploads/2010/06/Apple-
II...](http://apple2history.org/wp-content/uploads/2010/06/Apple-IIGS-control-
panel.jpg)

~~~
gefh
UK Apple ][e's came with a switch under the keyboard to change $ to £, so
Apple was not immune from this approach.

~~~
peteri
Nope it changed # to £ by switching the character ROM instead. I think it also
swapped keyboard layouts (i.e. AZERTY to QWERTY) but that wasn't an issue for
UK folks.

------
i386
Anyone remember cutting themselves really badly on AT cases? I still have
scars from raiding a bunch of ex-office machines

~~~
jsmit
Yes! The biggest scar on my body is a 3cm long cut in the shape of the eye of
Sauron from the edge of an AT case. Dangerous stuff fiddling with computers
back in the day.

------
ivanche
I still remember when I made my dad to open the tower case of our 486 and
reconfigure jumpers located beyond the 7-segment display which showed the CPU
frequency. After 10 minutes we were done and I was so proud that, when turbo
is pressed, display showed 42 MHz. Oh, the memories...

------
grawprog
I was a kid at the time when we had a 486 and I was always scared of the turbo
button. I had no idea what it did. I remember pressing it once and fooled
around for a bit...nothing seemed to be different so I turned it off. I was
scared for a little while after that someone might have found out that I
pressed the turbo button...

For a long time after though, until we got a new computer, I would try turning
it on randomly playing games or doing different things. I remember coming to
the conclusion that it didn't do anything and we probably just didn't have
whatever the turbo mode was supposed to be for.

I forgot about all that until I read this. It's pretty cool to find out after
all these years it actually did do something.

------
teh_klev
My first PC, bought back in the summer of 1986, was an Opus (now defunct UK
clone builder) with a 12MHz 286 processor, 1MB of RAM and a 37.5MB (RLL not
MFM) 3.5" hard disk. It cost me an eye watering GBP 1200 (I was still a
student at the time). However it did pay for itself quite quickly doing homers
in knocking out dBase II and dBase III "apps" (and eventually Clipper stuff).

This thing had a turbo button on the front which would switch the CPU between
4.77MHz and 12MHz. I never had a need to run in 4.77 mode except for nostalgia
purposes (I bumped into IBM PC's and compatibles quite early on).

------
jnurmine
My 386sx/25MHz also had a turbo button. It was rather useless, as I wanted the
machine to go faster, not slower...

Here's another turbo-nostalgia memory from further back:

The Commodore C64 tape drive had a small hole which let you adjust the tape
head azimuth to get a better signal. Sometimes, after borrowing tapes with
games from a friend, one had to do adjustments as the turbo loader did not
load the game correctly.

Hence the adjustment screw was called "the turbo screw".

------
trumped
I remember those games that were too fast on "newer" CPUs... unfortunately I
don't have this problem anymore and the games are not that much better...

~~~
morganvachon
Same, I recall upgrading from a 286 to a 486 in the 90s, and on the new
computer, Lemmings was way too fast to play. It didn't have a turbo button and
I wasn't allowed to tinker with the guts, so there was no way to slow it down.

------
bayindirh
My 486DX had one. It actually connected to the MB, and controlled the CPU
speed. Some games like Prehistorik 1/2 had slowed down considerably when I
toggled the button.

The button was also wired handsomely. When untoggled (out position), the Turbo
LED was lit and system was fast. When pressed, LED is turned off and system
was slow. Since all buttons (Power, Turbo and Reset) were flush, it was
aesthetically pleasing too.

------
ryanmercer
Heh I had many computers with turbo buttons, including a few Pentium II slot
processor machines. Oh man, slot processors. Slot 1 was so weird.

------
bdamm
My first PC had two turbo buttons; one on the case for the CPU, and another on
the modem to cap at 300 baud or allow blazing 1200 baud.

------
solidr53
Police Quest was simply impossible without the turbo button back in the day.
Or that is, until I discovered the menu bar by accident.

~~~
bitwize
Despite being released around the beginning of the 486 era, Space Quest IV
still had CPU-speed-sensitive timing. It was fine on a 386, but on a
Pentium-60, the chances that the patrol droid would appear and kill you
instantly at the beginning bit of the game got close to unity.

------
NVRM
Slowing down a computer is useful when programming, but isn't easy to do. I
had made my own tool to slow down network connexions, maybe useful to someone:
[https://github.com/webdev23/kamtar](https://github.com/webdev23/kamtar)

~~~
majewsky
The Devtools in Firefox have this built in (a slow network simulator).

~~~
NVRM
Yes, but can't switch off.

------
raldi
We had an IBM PC XT with an expansion board that upgraded the 8088 to a 80286.
To drop speeds back to approximately what they used to be, or toggle back, you
would hold both shift keys at the same time, and it would respond with either
a high- or low-frequency beep.

~~~
RHSeeger
If you don't mind me asking, is it possible you're misremembering? I believe
the XT/286 was actually a different computer than the XT, and ran a 286 on the
motherboard; it did not upgrade to 286 via expansion board.

I have fond memories of my XT/286.

~~~
Tagbert
The 80286 went into the IBM PC AT. The XT was the one with the 8088 chip.
However after the AT 80286 came out, it was possible to get an upgrade card
for the XT 8088 that was essentially an 80286 and motherboard on a card. It
was like brain transplant for your computer. It wasn't as fast as running a
real AT but it was cheaper and a lot faster than the 8088.

~~~
RHSeeger
This doesn't sound right to me. We had an XT/286 and I don't recall any
expansion card involved. Wikipedia seems to agree with me that it was a
totally separate model. That being said, it doesn't include a citation for the
info, so it's possible it's incorrect.

[https://en.wikipedia.org/wiki/IBM_Personal_Computer_XT](https://en.wikipedia.org/wiki/IBM_Personal_Computer_XT)

~~~
edmccard
>We had an XT/286 and I don't recall any expansion card involved...

And other people had an XT that they installed an expansion card into -- like
the Pfaster-286[1]

[1][https://books.google.com/books?id=xsMx9D2s6y0C&pg=PA43&lpg=P...](https://books.google.com/books?id=xsMx9D2s6y0C&pg=PA43&lpg=PA43&dq=286+expansion+board&source=bl&ots=_lFrag8VIf&sig=_75OVAZvvnkxp6V8pilMbC3rA_k&hl=en&sa=X&ved=2ahUKEwivn7jxrMbcAhVMn-
AKHUkTAn4Q6AEwDXoECAkQAQ#v=onepage&q=286%20expansion%20board&f=false)

------
Drdrdrq
From time to time I still miss turbo button and a (functioning) pause key. On
DOS you could pause execution to inspect output... I guess with
multiprocessing it became more difficult to implement this...

~~~
moviuro

      pkill -STOP "$(xprop _NET_WM_PID)"
      pkill -CONT "$(xprop _NET_WM_PID)"
    

This might have some unintended consequences though (file locks, clock drift
between running program and your quartz...).

Regarding turbo, I'm pretty sure a shell script could set the CPU's speed
governor to "conservative" at the press of a button.

~~~
Drdrdrq
Thanks, it's not quite the same though. Pause key was much more convenient,
and worked on every system. Thanks nevertheless!

~~~
moviuro
Also, for terminals that support it: `Ctrl+S` to pause the display only (the
command continues to run) and `Ctrl+Q` to unpause. Still not perfect... but it
could help sometimes.

------
macjohnmcc
I just built a PC today and the motherboard has a switch for "slow mode". This
is a modern system.

~~~
gattilorenz
What motherboard?

~~~
detaro
Bunch of high-end gaming motherboards (at least some models from ASUS and MSI)
have that, for extreme overclockers as a "safety switch" to clock down the
system while they are changing settings (where otherwise the system would
crash in the meantime due to overheating)

------
Rodyland
My first every PC, in high school. I changed the jumpers on the turbo button
to read "69".

------
ronreiter
Love reminders of how old I am :)

------
pjmlp
Yep I got one on my brand new 386SX 40 MHz back in the day.

Turbo would switch it between 20 and 40 MHz.

