Subject: RE: [hackers-il] Turbo button on old PCs

From: "Arik Baratz" <[email-masked]>
Date: Thu, 29 May 2003 16:05:51 +0300

Hi Chen

The "turbo" button actually changed the CPU's hardware clock from whatever it was the CPU could handle at the time (8, 10, 12MHz) to the original PC one, 4.77MHz.

-- Arik

-----Original Message-----
From: Chen Shapira [mailto:[email-masked]]
Sent: Thursday, May 29, 2003 1:50 PM
To: [email-masked]'
Subject: [hackers-il] Turbo button on old PCs

Hi, 
I suddenly remembered that old PCs had a "turbo" button, clicking on that was supposed to speed up the PC in some way. 
This button no longer exist in modern PCs. 
Any idea what this button did? (if anything at all?) Why didn't they simply make the PC go faster all the time? And why did they remove that button?
Thanks, 
Chen 

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From: "Nadav Har'El" <[email-masked]>
Date: Thu, 29 May 2003 16:34:37 +0300

> The "turbo" button actually changed the CPU's hardware clock from whatever it was the CPU could handle at the time (8, 10, 12MHz) to the original PC one, 4.77MHz.

Wow, this "4.77" number brings back memories ;)
I suddenly remembered where the 18.2 clock interrupts per second (that I
mentioned in an earlier mail) came from: take a 4.77MHz clock, divide it by
2^18 (4*65536) and you get 18.196 Hz :)

I can't believe I actually remembered that 18.2 number - it's been been
12 years since I last did any low-level DOS programming... :)

Interestingly, this 18.2 Hz figure also means that there are almost exactly
65536 (2^16) timer interrupts per hour. I wonder if this was by accident, or
the reason the numbers "4.77" or the division by 4 mentioned above, were
chosen.

-- 
Nadav Har'El                        |     Thursday, May 29 2003, 27 Iyyar 5763
[email-masked]             |-----------------------------------------
Phone: +972-53-245868, ICQ 13349191 |We aim to please, you aim too, please.
http://nadav.harel.org.il           |(sign in a gas station men's room)