Hacker Newsnew | past | comments | ask | show | jobs | submitlogin

Do I recall correctly that those turbo buttons would, counterintuitively, actually down-clock the CPU? For compatibility with software that had hard-coded timings or something?


The correct way to wire them is so that turbo "on" means full speed and turbo "off" means slowed down. Different motherboards implemented it differently. Usually downclocking the FSB or inserting waitstates for memory access.

They originated with "Turbo XT" class machines which ran an 8088 but at 8, 10 or 12 MHz -- faster than a real IBM PC/XT. Turbo on meant a faster machine, and turbo off meant 4.77 MHz -- fully compatible with timing-sensitive PC software.

Later, in the 386/486 whitebox PC era, some machines had the buttons wired wrong and now it's a meme that turbo made the computer go slower, but that was never true for systems built correctly.


Yes. Old software had timing loops and other delay constructs. For a while, that button was meaningful when running games intended for the original clock rates.


I discovered this a few years ago playing Ultima IV on my Amiga 3000, which is 16Mhz. It was impossible to play (and funny to look at) because the game was so sped up. All of the NPCs in the game, which normally just stand in place and move their arms about, were moving so fast it was bananas. You could barely see their arms they were like hummingbirds.

The game was intended to be on a 7Mhz stock machine pre-1990. And it was perfectly timed to that speed.


Indeed. Same story here. The Atarisoft port of ROBOTRON for DOS was that way. Insane at any two digit clock.

Sidebar: Ultima games are great. Did you see Nox Archaist?


Wow - that is quite the unabashed Ultima clone right there!


Seriously. The guy put in a good amount of time and delivered an Altima with many modern sensibilities baked in. I've been playing it on my Apple it's a lot of fun.




Guidelines | FAQ | Lists | API | Security | Legal | Apply to YC | Contact

Search: