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Lucky Star 5i-VX2B only 100Mhz

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First post, by 8bitplus

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]Hello Everyone.
I have a very nice baby AT Lucky Star 5i-VX2B socket 7 motherboard at the centre of my retro games rig, running a 100mhz Pentium. All working great.
I'm trying to get it working at 200Mhz with a newer MMX P55C Pentium and just not getting anywhere.

The attachment Motherboard[1].jpg is no longer available

The motherboard manual states the jumper config for the above CPU and does indeed support it so thats' a good start.
I've selected 2.8v VCORE voltage, 66MHZ Clockspeed, and x3 ratio but just get no post until I swap back in the old 100Mhz chip (and reset jumpers)

At first I thought it was because I was trying the later "Plastic" packaged processor, but yesterday I got hold of a ceramic unit and its exactly the same.

Is there anything more I can try before finding another motherboard? I believe the BIOS is the latest version and works well with HDDs over 8Gb.....

Motherboard info here:
https://stason.org/TULARC/pc/motherboards/L/L … um-5I-VX2B.html

Thanks 😀

Reply 1 of 2, by derSammler

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The 100 MHz Pentium is single voltage, the MMX is dual-voltage. Could be that the VRM for the dual-voltage rail is dead, hence the CPU never gets power. Check if the 2.8V are really there. But make 100% sure first that all jumpers are really correct for the MMX.

Reply 2 of 2, by 8bitplus

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Hi derSammler
Good suggestion. The symptoms could be that.
do you think I should get a 2.8v reading from the voltage selection jumper?

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