VOGONS


First post, by foil_fresh

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I've got a Lucky Star Slot 1 440BX motherboard and have bought a P2 266 Klamath to do some underclocking for DOS games - this board has it's multi and fsb clock settings in BIOS not switches/jumpers, making it ideal for this unlocked P2.

Browsing through the manual I saw something that stood out - TURBO66

"TURBO66 is an over-clocking jumper which enables 66 MHz CPU to run at 100 MHz. TURBO66 is only reserved for internal test only. No guarantee is provided for over-clock setup."

Should it be connected to a switch or momentary connection? Sadly the only AT case I have is baby-AT and won't take this sized board. Any reccomendations for 3.5" or 5.25" bays that have a turbo switch?

ideally if this thing can be switched while the pc is on, then i can quickly go between 250mhz (100 x 2.5)and 166mhz (66 x 2.5) without rebooting - perfect for any dos game that gets divide errors when running on CPUs at over 200mhz.

http://www.elhvb.com/mboards/luckystar/manual … BX2V/6abx2v.pdf

any other boards with this jumper? thoughts? does anyone have experience with this kind of jumper?

cheers

Pentium MMX 166MHz / Shuttle HOT591-p / S3 Trio3d2x / SB 16
Pentium II 266MHz / Lucky-Star 6ABX2V / Riva128 / AWE64 / AW744L
Pentium III 950 MHz / SY-7VBA / Voodoo 3000 / Aureal Vortex 2
Pentium IV 3.4GHz/ GA-8S655FX / Geforce 6800 GT / Audigy

Reply 1 of 10, by Horun

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Ok that would be a switch (just like a jumper) for your purpose. I doubt you should ever switch speeds while it is on, based on the fact it is made for a jumper. It is not like the turbo switch on XT, 286 and some 386. Any old full size AT case with a turbo switch should work. No do not have a board with that exact jumper but have some old boards with OC override capabilty.

Hate posting a reply and have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. 🤣

Reply 2 of 10, by foil_fresh

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i've seen people hook multiplier jumpers up to turbo swtiches which can be changed on the fly without hazard (but it doesn't actually use the chosen multiplier until the next boot when the pins are actually in effect) so im just wondering if it's an instant fsb change or next boot type situation.

the cpu arrives in ~3 weeks so i'll just have to test it when it gets here. its not a massive game changer if the turbo66 jumper works or not because the bios is fairly capable.

Pentium MMX 166MHz / Shuttle HOT591-p / S3 Trio3d2x / SB 16
Pentium II 266MHz / Lucky-Star 6ABX2V / Riva128 / AWE64 / AW744L
Pentium III 950 MHz / SY-7VBA / Voodoo 3000 / Aureal Vortex 2
Pentium IV 3.4GHz/ GA-8S655FX / Geforce 6800 GT / Audigy

Reply 4 of 10, by derSammler

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H3nrik V! wrote on 2020-03-11, 12:13:

IIRC, the CPU only checks the 66/100MHz pin at boot-time, so probably won't be able to change speed on the fly, without a reset ..

That check has nothing to do with the speed it runs at. That's just the lock and it will refuse to run if locked and wrong FSB speed is used.

Switching FSB speed on-the-fly normally works fine. I've built two systems with such a switch and there are no issues.

That header, however, is not meant for non-factory use. It may not work when switched on-the-fly (or not at all).

http://retro-net.de/blog.html

Reply 5 of 10, by H3nrik V!

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derSammler wrote on 2020-03-11, 12:18:
That check has nothing to do with the speed it runs at. That's just the lock and it will refuse to run if locked and wrong FSB s […]
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H3nrik V! wrote on 2020-03-11, 12:13:

IIRC, the CPU only checks the 66/100MHz pin at boot-time, so probably won't be able to change speed on the fly, without a reset ..

That check has nothing to do with the speed it runs at. That's just the lock and it will refuse to run if locked and wrong FSB speed is used.

Switching FSB speed on-the-fly normally works fine. I've built two systems with such a switch and there are no issues.

That header, however, is not meant for non-factory use. It may not work when switched on-the-fly (or not at all).

Yeah, on second thoughts, it's only the multiplier pins, that are read at boot time only, as the multiplier is the CPU's function, and the FSB is the board's

Reply 6 of 10, by foil_fresh

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derSammler wrote on 2020-03-11, 12:18:

Switching FSB speed on-the-fly normally works fine. I've built two systems with such a switch and there are no issues.

That header, however, is not meant for non-factory use. It may not work when switched on-the-fly (or not at all).

if you dont mind me asking, what kind of systems and how were they set up? does it actually change FSB instantly? thanks

Pentium MMX 166MHz / Shuttle HOT591-p / S3 Trio3d2x / SB 16
Pentium II 266MHz / Lucky-Star 6ABX2V / Riva128 / AWE64 / AW744L
Pentium III 950 MHz / SY-7VBA / Voodoo 3000 / Aureal Vortex 2
Pentium IV 3.4GHz/ GA-8S655FX / Geforce 6800 GT / Audigy

Reply 7 of 10, by derSammler

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Sure, these two:
Flytech Carry-1 S370-based mini PC (2001)
AMD 5x86 X5-133 (now with POD)

//edit:
Three, actually. Forgot this one:
My Intel Plato/Premiere II build

In all cases, one jumper for FSB speed is connected to a toggle switch.

http://retro-net.de/blog.html

Reply 8 of 10, by foil_fresh

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ok thats great, i'm really hyped to try this turbo header to see how it works. btw nice and strong little p3 system!

Pentium MMX 166MHz / Shuttle HOT591-p / S3 Trio3d2x / SB 16
Pentium II 266MHz / Lucky-Star 6ABX2V / Riva128 / AWE64 / AW744L
Pentium III 950 MHz / SY-7VBA / Voodoo 3000 / Aureal Vortex 2
Pentium IV 3.4GHz/ GA-8S655FX / Geforce 6800 GT / Audigy

Reply 9 of 10, by bofh.fromhell

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I suspect its the B21 trick it uses:
http://www.thg.ru/cpu/19980514/print.html
Quite common on motherboards aimed at enthusiasts.
Most if not all P2's were "vulnerable" to this until Intel realized ppl even used it in servers and sorted it in the CPU's.

Reply 10 of 10, by foil_fresh

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thanks for the link, will give it a read

Pentium MMX 166MHz / Shuttle HOT591-p / S3 Trio3d2x / SB 16
Pentium II 266MHz / Lucky-Star 6ABX2V / Riva128 / AWE64 / AW744L
Pentium III 950 MHz / SY-7VBA / Voodoo 3000 / Aureal Vortex 2
Pentium IV 3.4GHz/ GA-8S655FX / Geforce 6800 GT / Audigy