13 ms·
This sounds similar to how the 8088 XT motherboards could be toggled with a turbo button on the front of the case.
by jon_adler 5y ago
This sounds similar to how the 8088 XT motherboards could be toggled with a turbo button on the front of the case.
- franga2000 5y agoDo 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?
- ddingus 5y agoYes. 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.
- erickhill 5y agoI 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.
- ddingus 5y agoIndeed. 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?
- einr 5y agoThe 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.
- ddingus 5y agoThere were cards that had a pot on the back. You could just dial up more speed, until your machine ran poorly, then back off just a little. Kind of crazy to think about! The speed on my Apple FastChip is adjustable in real time too. It's neat to just dial a speed appropriate for the application at hand.
- cogburnd02 5y agoI had not heard of the FastChip before today, so thanks for letting me know it exists. :-D for other interested parties: http://www.a2heaven.com/webshop/index.php?rt=product/product&product_id=147 http://www.a2heaven.com/webshop/index.php?rt=product/product...
- ddingus 5y agoIt's a great product! If you are interested in programming your Apple in assembly, you can ask nicely for your FastChip to include a 65816 processor. It's going to act like a 65802, due to hardware limitations, but otherwise yeah. You get the 16 bit instructions to use. I've not had any compatibility trouble with mine, which is a 65816.
- ddingus 5y agoIt also runs at less than 1mhz. That is just as interesting, frankly.
- necovek 5y agoI am pretty sure I've had this on at least my 80286, and maybe even 80386 and 486DX2 (33/66MHz I think) too (though highly uncertain on the latter). Perhaps you only needed a case that would connect the turbo switch to the motherboard. It was fun to turn it on for games that used timing-loops for frame rendering to make games twice as fast :)