Strange Mainboard behaviour- DFI P5BV3+ successfully POSTs, but does not boot \ VOGONS

Strange Mainboard behaviour- DFI P5BV3+ successfully POSTs, but does not boot

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First post, by trekkie22

Posted on 2024-09-15, 18:29

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I recently bought a DFI P5BV3+ Super Socket 7 board for an AMD K6-2/450 Retro PC I'm currently building.

The board has a really strange behaviour. It POSTs, it detects drives, etc., the EPA Logo and the footer goes away but then it does not switch and try to boot the OS, but it either hangs or just resets.
I first assumed it is a flipped bit in the BIOS Flash, so I flashed a new BIOS using a USB Programmer, but it doesn't change the behaviour - tried every BIOS version on the Retro Web.

Power is not an issue, I'm using a modern ATX power supply (BeQuiet System Power 9 400W) and also tried it with a PicoPSU. I also measured all Voltages - All power rails, including the ones generated on the board, are spot on.

As far as I know, the poing of failure should be the time it does Plug&Play Autoconfiguration. So I also tried all the available options for that, but also no change. I even disabled every component on the board in the BIOS settings. Theres' nothing on the board but the graphics card. It's a known-good Matrox Millennum G400 that works flawlessly on another board.

I am at a loss what happens here. As it won't let me boot anything i have no means of using test software.

Any ideas on how to narrow this down to the root cause are appreciated.

Reply 1 of 9, by Repo Man11

Posted on 2024-09-15, 18:52

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Will it boot from a floppy disk?

"We do these things not because they are easy, but because we thought they would be easy."

Reply 2 of 9, by trekkie22

Posted on 2024-09-15, 20:19

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Unfortunately not. It boots from nothing. The EPA logo goes away and then it either hangs or resets, it does not even show the configuration summary.

Reply 3 of 9, by dominusprog

Posted on 2024-09-15, 20:24

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Have you tried a different RAM stick?

A-Trend ATC-1020 V1.1 ❇ Cyrix 6x86 150+ @ 120MHz ❇ 32MiB EDO RAM (8MiBx4) ❇ A-Trend S3 Trio64V2 2MiB
Aztech Pro16 II-3D PnP ❇ 8.4GiB Quantum Fireball ❇ Win95 OSR2 Plus!

Reply 4 of 9, by Mr_Magoo

Posted on 2024-09-15, 20:28

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What harddisk do you have attached? I had the same behaviour by using an IDE-to-CF-Card adapter. After changing it with another one, it bootet into DOS. What is your exact setup?

Reply 5 of 9, by ux-3

Posted on 2024-09-15, 21:03

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ISA VGA?
AGP/PCI VGA?
try fsb 66
Did you check CPU voltage settings?
Swap in a regular Pentium?
Use single sided ram , max 64 MB.

Retro PC warning: The things you own end up owning you.

Reply 6 of 9, by Horun

Posted on 2024-09-16, 02:16

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Yeah I would set it as a K62-300 (66Mhz and 4.5x) just to see what happens. From manual: "We do not guarantee that 75MHz, 83MHz, 95MHz and 100MHz external system bus clock processors will work with all types of add-in cards, memory modules or other devices.".

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 7 of 9, by trekkie22

Posted on 2024-09-19, 08:54

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I'm actually waiting for supplies to try everything you mentioned.

Needs a few days until I can try with another RAM stick and another CPU. Setting the CPU to a lower clock speed made no difference, also using another graphics card.

Harddisk is not the problem, it hangs with and without any peripherals on the same spot. I'll make a video from the next try to clarify the exact behaviour.

Reply 8 of 9, by trekkie22

Posted on 2024-10-10, 15:45

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I think I found it. The clock generation for 60 and 66 MHz clocks seems to be bad.

I bought myself a Pentium MMX 133 and a single sided RAM Stick. The Pentium MMX does not work at all if set to 60 or 66 MHz, the board does not even start to POST, but the Chip gets hot. It works only with the 75 MHz setting, but with the same fault as I described later in the boot process. Took some time to realize that it might be the clocks and do some experimenting. First had to verify with a retro friend that it's not the new CPU that's at fault.

As 60/66 MHz is the AGP Clock even if the Processor is set to higher base clocks, It has to be generated independently.
The CPU gets hot when set to 60/66MHz so it seems the clock is generated, but seemingly so out of spec that the Pentium can't handle it. Kudos to AMD and Matrox that the K6/2 and the Millennium G400 do work at least for most of the POST phase...

Oscilloscope time at the weekend to verify this theory.

Reply 9 of 9, by Pino

Posted on 2024-10-10, 15:53

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Mr_Magoo wrote on 2024-09-15, 20:28:

What harddisk do you have attached? I had the same behaviour by using an IDE-to-CF-Card adapter. After changing it with another one, it bootet into DOS. What is your exact setup?

It took me forever to find why my IDE-to-SD card adapter didn't work with my VIA MVP3 Board.

You need a really short IDE cable or even better use a 80 pin IDE cable.

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