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Rauli
April 30th, 2014, 02:38 AM
Hi everyone! I have received an Elpina M571 motherboard, for Pentium, MMX, Cyrix 6x86, AMD K5/K6 and IDT C6, WinChip.

It came with an IDT C6 and with this processor it works correctly.

I would like to use this board to test processors, because:
It supports almost the full range of Pentium clones.
It is easy to set the jumpers (they are documented on the board itself).
I don't need to connect nothing (it has disk connectors, and it has an integrated VGA) but the power supply.

The problem is that it has a SMD component soldered between pins X02 and X04 of socket 7.

According to the data sheet of every processor listed at the beginning, those pins are VSS (ground) and BRDY#

I know that people add resistors to reduce voltage to use low-voltage processors (the minimum supported by the board is 2.2V), but these resistors are added near the voltage regulator, not between socket 7 pins.

As I don't know the purpose of this mod, I can't dare to change the actual processor or configuration, because some mods work for a certain configuration and prevent other configurations to work.

Does anybody know what this modification is for? Is it a known hack for Pentium boards?

Uniballer
April 30th, 2014, 08:14 AM
I guess the obvious question is, what is the component? BRDY# means "burst ready" in the low state (read or write bus transaction completed). Maybe a resistor or very small capacitor was added to reduce ringing on this input? Maybe a diode was added to eliminate undershoot?

Uniballer
April 30th, 2014, 08:54 AM
Have you been to this M571 site (http://m571.com/m571/)?

Rauli
April 30th, 2014, 10:02 AM
Thanks for replies. Yes, it is essential to know what the SMD component is, but I can't see any markings on it. Anyway I will try to use a magnifying glass because it is very small. A photo would not help a lot with SMDs, would it? Also, I don't have much electronic background, I understand "burst ready", but not "ringing" or "undershoot". Could any of these 2 possibilities prevent other CPUs to work? Or damage them?

I forgot to mention that in the present (working) configuration, the FSB speed, multiplier and voltage jumpers are correctly set for the used CPU (markings: 200 MHz and 3.52V, jumpers: 66 MHz, mult x3, 3.5V) so I understand that it is not an attempt to overclock it, or to modify voltages.

And, yes, looking for information I found the M571 site (very interesting for owners of these boards). This hack is not explained there. All the hacks presented there are related to voltage regulation.

BTW, other advantages of this board is that it has connectors for both AT and ATX power supplies, and can use 72 or 168-pin memory modules. It's very flexible!

Uniballer
April 30th, 2014, 10:20 AM
A photo might be helpful, if it has enough resolution. I don't have a macro lens, but I have had surprisingly good luck with photographing items viewed through a lighted magnifier.

rmay635703
April 30th, 2014, 02:33 PM
A photo might be helpful, if it has enough resolution. I don't have a macro lens, but I have had surprisingly good luck with photographing items viewed through a lighted magnifier.


??? I would just use the board for tests, If worried YOU CAN check the voltage provided by each jumper setting without a cpu in the socket if you want, just need some needles and a multimeter.

The only thing that could damage a cpu is
1. Wrong Voltage
a) Unified I/O and Core voltages
2. Grounds in places it doesn't belong

So rock ahead and no worries.

That said, I used to deal in PC Chips m571s and their m569 cousins in the late 90's and early 2ks. All of mine were good to 83mhzFSB - 500mhz CPU and 2.5v core

I always liked not having to by what was at the time a very expensive low end PCI video card and I loved using up mix mashes of SD and FPM in the boards.

If you won't mind being limited to older CPUs you can use the old m569 bios (its been many years I will need to double check) It won't see k6-2s but then you can use 256mb SDRAM modules safely.

Good Luck, I always enjoyed those old boards.

Cheers
Ryan

Rauli
May 1st, 2014, 03:41 AM
Sorry, but this is the best photo I could take.
18548

Uniballer
May 1st, 2014, 04:56 AM
It looks like a cap to me, but it is hard to be sure. You could try removing the CPU and measuring it with a multimeter if you have one, but that might not tell you much.

I agree with rmay635703 in that while it might not work with a different CPU it is unlikely to damage anything. Or you could remove the component and see what happens...

Rauli
May 1st, 2014, 11:12 PM
Mmm... my multimeter has no capacitor measurement capability. I will try to remove the component only if something doesn't work, because my experience with solder iron and such small parts is not very positive...

But, from all the feedback (thank you very much) I understand that chances are not to damage anything.

And being related to the BRDY# signal, my conclussion (which could be wrong) is that if I test the board at any FSB speed and it works, I will have no problem.