More fun. I was able to set multiplier 1x on the IBM 6x86L. 😀

A little experimenting showed that jumper JP6, which is "reserved" actually controls BF2. With the FSB set at 50, JP1=JP2=JP6 in position 2-3, the multiplier was set to 1x on the IBM CPU and it POSTed at 50MHz.
So now we know what JP6 is for.

JP1=BF0; 1-2="1", 2-3="0"
Jp2=BF1; 1-2="1", 2-3="0"
JP6=BF2; 1-2="1", 2-3="0"

This will allow setting any supported multiplier on any socket7 CPU.

...for instance on K6-2 CPUs according to this table taken from the datasheet https://www.amd-k6.com/wp-content/uploads/201 … p_Datasheet.pdf page 92

stamasd wrote on 2022-01-23, 14:12:

Hmm yes and there is indeed a difference between the Cyrix-branded and the IBM-branded 6x86 chips. According to that table, the jumper combination that results in a 1x multiplier on Cyrix chips should give a 2x multiplier on IBM chips.
And practically, after unbending the pins on the IBM 6x86L-PR166+ and installing it with FSB=50 and JP1=JP2=2-3, it POSTS as a "6x86L-PR120+" which means it's running at 100MHz (not 50 as the Cyrix chip did). Still cool, but that means 50MHz is not achievable on this board with IBM CPUs, because there is no jumper to control BF2 and that would be the only method to get 1x for IBM.

There may be a multiplier lock implemented. I noticed that on pentium chips that I recently tested that some would remap lower multipliers if the upper multipliers had been messed with

Some would do 1.5x, some would do 2x on 2x setting etc.

stamasd wrote on 2022-01-23, 15:23:

More fun. I was able to set multiplier 1x on the IBM 6x86L. :) […]
Show full quote

More fun. I was able to set multiplier 1x on the IBM 6x86L. 😀

A little experimenting showed that jumper JP6, which is "reserved" actually controls BF2. With the FSB set at 50, JP1=JP2=JP6 in position 2-3, the multiplier was set to 1x on the IBM CPU and it POSTed at 50MHz.
So now we know what JP6 is for.

JP1=BF0; 1-2="1", 2-3="0"
Jp2=BF1; 1-2="1", 2-3="0"
JP6=BF2; 1-2="1", 2-3="0"

This will allow setting any supported multiplier on any socket7 CPU.

Excellent! 😁

Hi stamasd, I just got the same motherboard like you and really like it for SDRAM and MMX suppot, but I have some difficulties with MB so was trying google and found your topic. I'll be glad if you or anybody else can help...

The problem is that all time I restart the computer and doesn't matter if with reset button, CTRL+ALT+DEL or just by exit from BIOS the PC won't boot up again and finish with black screen. I have to power off and power on again... I can see I have same bios version so it is not the case, any idea what could be wrong?

Thanks!

koroner wrote on 2022-03-16, 15:34:

Hi stamasd, I just got the same motherboard like you and really like it for SDRAM and MMX suppot, but I have some difficulties with MB so was trying google and found your topic. I'll be glad if you or anybody else can help...

The problem is that all time I restart the computer and doesn't matter if with reset button, CTRL+ALT+DEL or just by exit from BIOS the PC won't boot up again and finish with black screen. I have to power off and power on again... I can see I have same bios version so it is not the case, any idea what could be wrong?

Thanks!

I’ve had some add in cards cause this before.

Sphere478 wrote on 2022-03-16, 21:41:

I’ve had some add in cards cause this before.

Unfortunately not the issue, only graphic card is installed so I tried different one in different slot but still same, also tried boot without FDD and HDD, changed simm to SDRAM and seems like MB issue..

Strange is that if I reset before "Award Plug and Play BIOS Extensions" shows up the computer restarts normaly.... any idea?

snufkin wrote on 2022-01-20, 21:08:

I know some Intel chipsets don't support async, so it'll be interesting to know if that works when you can try it. […]
Show full quote

stamasd wrote on 2022-01-20, 19:20:

Like I mentioned above, this board's clock generator has the ability to run the PCI clock at a constant 32MHz independent of the FSB.

I know some Intel chipsets don't support async, so it'll be interesting to know if that works when you can try it.

[edit: I've marked on the photos what I think are the pins you've found (obviously waiting for when you can check the PS/2). Do they look right?]

[edit: I've updated the COM port and removed the previous picture, hopefully that's now correct]

Belated reply. I finally got around to working on this motherboard again.
I made a custom adapter for the PS/2 port. Tried with both pin 1 = DATA and pin 3 = CLK, and the other way around. None of the 2 configurations work, a PS/2 mouse is not detected/usable with either of them. I used pin 4 = GND and pin 5=Vcc in both cases.

This is an old topic, but in case someone else struggles to find the correct mouse pinout, then my PCPartner
TXB820DS (35-8333-01) has the following pinout:

1 - Data
2 - Ground
3 - CLK
4 - NC
5 - +5V

Numbers correspond to the op markings.

I know the OP has tested this variation, but maybe his was broken, because I don't believe 35-8333-01 and 35-8333-03 have different pinouts as the layout is otherwise the same.

Zida Tomato C-Series Mainboards Cable Set has a mouse cable that has 5 pins in a row, but just need to be rearranged. If you have one of those, then the colors would be:

1 - Data (Blue)
2 - Ground (Yellow)
3 - CLK (Red)
4 - NC (empty)
5 - +5V (Green)