Charleston wrote on 2021-07-24, 20:29:

Issue with this is that a dx4 is 33.3x3 not 50x2 to reach 100mhz. The dx4 only works when set specifically to 50mhz as it was setup for the sx or dx2 50. 3x clock will boot for moments before crashing in bios.

With the original settings with the 50mhz cpu in place, it was set to 3x which would be 75hz. I think the jumpers are wrong. I'm just highly confused.

DX2 CPUs are, in modern terminology, multiplier-locked to 2. So a DX2-50 will not pay any attention to the multiplier jumpers. In addition, it should be set for 25 MHz, not 50.

Might it be a DX-50?

jakethompson1 wrote on 2021-07-24, 20:35:

Charleston wrote on 2021-07-24, 20:29:

Issue with this is that a dx4 is 33.3x3 not 50x2 to reach 100mhz. The dx4 only works when set specifically to 50mhz as it was setup for the sx or dx2 50. 3x clock will boot for moments before crashing in bios.

With the original settings with the 50mhz cpu in place, it was set to 3x which would be 75hz. I think the jumpers are wrong. I'm just highly confused.

DX2 CPUs are, in modern terminology, multiplier-locked to 2. So a DX2-50 will not pay any attention to the multiplier jumpers. In addition, it should be set for 25 MHz, not 50.

Might it be a DX-50?

Honestly I've got no clue, I got it with the board. The board was originally set to cyrix jumpers but the 50 was advertised as an a80486 intel 50mhz. Could be sx2, dx, or dx2 for all I know. Setting the jumpers for 25mhz is the exact same setting as setting for 50mhz by the way. The only difference is dependent on what you set the clock to. 2x, 2.5x, or 3x. Although the clock multiplier says it only works with dx4 which would explain what you said exactly.

Charleston wrote on 2021-07-24, 20:38:

Setting the jumpers for 25mhz is the exact same setting as setting for 50mhz by the way. The only difference is dependent on what you set the clock to. 2x, 2.5x, or 3x. Although the clock multiplier says it only works with dx4 which would explain what you said exactly.

No, it's not the same setting. 25MHz is JP38 open/JP39 closed, but 50MHz is JP38 and JP39 both open. Maybe you are confused by "50iMHz", which is intended to mean 50MHz (internal), and actually means 25MHz for a CPU that operates at 25x2. That's why 50iMHz and 25MHz is the same configuration. If you board came with JP38 open/JP39 closed, it came with an SX2-50 or DX2-50 processor. If it came with both jumpers open, it came with a DX50 processor.

Charleston wrote on 2021-07-24, 20:29:

Issue with this is that a dx4 is 33.3x3 not 50x2 to reach 100mhz.

In fact, most DX4 processors operate perfectly at both 33x3 and 50x2, even if 50x2 is not officially supported by Intel.

EDIT: Horun looked up your processor, and found that your specific kind of DX4 is locked to x3, so you can't run it at 50x2.

Do you have a jumper cap on JP21? If that is indeed a Green PC connector, there should be no jumper there.

jakethompson1 wrote on 2021-07-24, 21:04:

Do you have a jumper cap on JP21? If that is indeed a Green PC connector, there should be no jumper there.

Nope, no jumper there.

mkarcher wrote on 2021-07-24, 20:54:

No, it's not the same setting. 25MHz is JP38 open/JP39 closed, but 50MHz is JP38 and JP39 both open. Maybe you are confused by "50iMHz", which is intended to mean 50MHz (internal), and actually means 25MHz for a CPU that operates at 25x2. That's why 50iMHz and 25MHz is the same configuration. If you board came with JP38 open/JP39 closed, it came with an SX2-50 or DX2-50 processor. If it came with both jumpers open, it came with a DX50 processor.

Ah I didn't know that. It came with 38 open and 39 closed so it's definitely a sx2 or dx2.

Edit: this is making me wonder if I need a different setting for 100mhz then? Maybe instead of 33mhz with a 3x clkmul use the 50 with a 2x like stated? Although I believe I've tried this and once I take out the 5v/3V jumper I get no boot.

Actually I do have a jumper on 21. Grnpc is 32 though. 21 is external battery (I think)

Correct me if I'm wrong

Are you sure your DX4 processor is good? There is no point in troubleshooting the mainboard if the processor is fried and just happens to work for some seconds on severe overvolting.

On the other hand, you said you have a scope. You might want to look at the Vcc for the processor in the 3V setting. 3.3V is fine, 3.45 is usual. 3.6V is acceptable, too. But the voltage has to be stable. If the voltage has a lot of jitter, you might need to replace some capacitors that stabilize Vcc.

mkarcher wrote on 2021-07-24, 21:22:

Are you sure your DX4 processor is good? There is no point in troubleshooting the mainboard if the processor is fried and just happens to work for some seconds on severe overvolting.

On the other hand, you said you have a scope. You might want to look at the Vcc for the processor in the 3V setting. 3.3V is fine, 3.45 is usual. 3.6V is acceptable, too. But the voltage has to be stable. If the voltage has a lot of jitter, you might need to replace some capacitors that stabilize Vcc.

Will take a look when I get to that step.

Also I've tried a couple different dx4 cpus. Amd and Intel both.

Charleston wrote on 2021-07-24, 21:17:

Actually I do have a jumper on 21. Grnpc is 32 though. 21 is external battery (I think)

Correct me if I'm wrong

Dunno, several sources say green PC. There is supposed to be a one-shot button connected to that not a jumper. Erratic behavior would be expected connecting a jumper. Especially when switching from non-SL to SL-aware CPU...

Agree probably a 3.3 voltage issue.
random thought: the jumpers for CPU type for DX, DX2 and DX4 are the same except jp40 and jp43. SX (and SX2) is not the same according to https://www.elhvb.com/webhq/models/486vlb3/v4p895v1.txt.html.
Do you have it jumpered for a DX2 ?

jakethompson1 wrote on 2021-07-24, 21:30:

Charleston wrote on 2021-07-24, 21:17:

Actually I do have a jumper on 21. Grnpc is 32 though. 21 is external battery (I think)

Correct me if I'm wrong

Dunno, several sources say green PC. There is supposed to be a one-shot button connected to that not a jumper. Erratic behavior would be expected connecting a jumper. Especially when switching from non-SL to SL-aware CPU...

Should I try just disconnecting both jumpers? If you look at my first image you can faintly see greenpc underneath a video card. I swore jp21 was some sort of external battery setting but maybe it's not?

Horun wrote on 2021-07-24, 21:31:

Agree probably a 3.3 voltage issue.
random thought: the jumpers for CPU type for DX, DX2 and DX4 are the same except jp40 and jp43. SX (and SX2) is not the same according to https://www.elhvb.com/webhq/models/486vlb3/v4p895v1.txt.html.
Do you have it jumpered for a DX2 ?

I have it all set for a dx4 at 33.3mhz with clkmul 3x but I've tried as many combinations as I can think of.

That manual is a bit off from what I have. There's also a win3x manual that more accurate I think

Charleston wrote on 2021-07-24, 21:33:

jakethompson1 wrote on 2021-07-24, 21:30:

Charleston wrote on 2021-07-24, 21:17:

Actually I do have a jumper on 21. Grnpc is 32 though. 21 is external battery (I think)

Correct me if I'm wrong

Dunno, several sources say green PC. There is supposed to be a one-shot button connected to that not a jumper. Erratic behavior would be expected connecting a jumper. Especially when switching from non-SL to SL-aware CPU...

Should I try just disconnecting both jumpers? If you look at my first image you can faintly see greenpc underneath a video card. I swore jp21 was some sort of external battery setting but maybe it's not?

From what you posted on elhvb, JP26 over by the keyboard port is the battery/clear cmos jumper.
I'd guess JP21 is sleep button and JP32 is sleep LED. Don't know what you mean by both jumpers. I would leave JP21 open though.

I recommend you to not try running DX4 processors at 5V. This might damage these chips, although it is known that they usually don't break immediately if you do.

Charleston wrote on 2021-07-24, 21:25:

Also I've tried a couple different dx4 cpus. Amd and Intel both.

jakethompson1 wrote on 2021-07-24, 21:30:

Erratic behavior would be expected connecting a jumper. Especially when switching from non-SL to SL-aware CPU...

If you happen to have a AMD DX4 with a "-NV8T" code on it, try getting that one to work first. The reason for recommending this kind of DX4 is that this processor doesn't support power management / SMI stuff (it is not SL-aware, as jakethompson1 says it), so if something is wrong with the "green" part of your mainboard, it won't affect the NV8T family of AMD DX4 processors.

jakethompson1 wrote on 2021-07-24, 21:36:

Charleston wrote on 2021-07-24, 21:33:

jakethompson1 wrote on 2021-07-24, 21:30:

Dunno, several sources say green PC. There is supposed to be a one-shot button connected to that not a jumper. Erratic behavior would be expected connecting a jumper. Especially when switching from non-SL to SL-aware CPU...

Should I try just disconnecting both jumpers? If you look at my first image you can faintly see greenpc underneath a video card. I swore jp21 was some sort of external battery setting but maybe it's not?

From what you posted on elhvb, JP26 over by the keyboard port is the battery/clear cmos jumper.
I'd guess JP21 is sleep button and JP32 is sleep LED. Don't know what you mean by both jumpers. I would leave JP21 open though.

Look below jp21 in my image. You can faintly see jp32 (grnpc)

I'll disconnect 21 too though.

mkarcher wrote on 2021-07-24, 21:37:

I recommend you to not try running DX4 processors at 5V. This might damage these chips, although it is known that they usually d […]
Show full quote

I recommend you to not try running DX4 processors at 5V. This might damage these chips, although it is known that they usually don't break immediately if you do.

Charleston wrote on 2021-07-24, 21:25:

Also I've tried a couple different dx4 cpus. Amd and Intel both.

jakethompson1 wrote on 2021-07-24, 21:30:

Erratic behavior would be expected connecting a jumper. Especially when switching from non-SL to SL-aware CPU...

If you happen to have a AMD DX4 with a "-NV8T" code on it, try getting that one to work first. The reason for recommending this kind of DX4 is that this processor doesn't support power management / SMI stuff (it is not SL-aware, as jakethompson1 says it), so if something is wrong with the "green" part of your mainboard, it won't affect the NV8T family of AMD DX4 processors.

Yeah my amd dx4 is a 8kb cache so I'll work on getting that one working and give up on the Intel for now.

Edit: it's sv8b not nv8t. Sorry

Charleston wrote on 2021-07-24, 21:37:

jakethompson1 wrote on 2021-07-24, 21:36:

I'd guess JP21 is sleep button and JP32 is sleep LED.

Look below jp21 in my image. You can faintly see jp32 (grnpc)

I'll disconnect 21 too though.

Jake Thompson tries to explain that JP32 is not a "green PC button connection", but a "green PC LED connector". Both of these functions can validly be labelled "grnpc". He expects that the green PC button (that should put the PC to sleep) is to be connected to JP21, and a jumper on that connection would look like a permanently depressed sleep button, which could disturb normal system operation. Your old 486SX2 processor doesn't contain the advanced power management features (most notably the system management mode), whereas most 486DX4 processors do. A permanently pressed sleep button might be ignored on processors without power management features.

Charleston wrote on 2021-07-24, 21:38:

mkarcher wrote on 2021-07-24, 21:37:

If you happen to have a AMD DX4 with a "-NV8T" code on it, try getting that one to work first. The reason for recommending this kind of DX4 is that this processor doesn't support power management / SMI stuff (it is not SL-aware, as jakethompson1 says it), so if something is wrong with the "green" part of your mainboard, it won't affect the NV8T family of AMD DX4 processors.

Yeah my amd dx4 is a 8kb cache so I'll work on getting that one working and give up on the Intel for now.

Edit: it's sv8b not nv8t. Sorry

The SV8B is identical to the Intel DX4 in that regard: It has the CLKMUL signal on the same pin as the Intel processor (which could have been a problem with the NV8T), and it supports power management and L1 write-back just like the Intel processor. There is no obvious advantage of one processor over the other for getting your board running. You should be aware that AMD processors don't support x2.5 multipliers and just don't start. So don't bother trying any AMD DX4 or 5x86 at x2.5. This option is Intel exclusive.

mkarcher wrote on 2021-07-24, 21:43:

Charleston wrote on 2021-07-24, 21:37:

jakethompson1 wrote on 2021-07-24, 21:36:

I'd guess JP21 is sleep button and JP32 is sleep LED.

Look below jp21 in my image. You can faintly see jp32 (grnpc)

I'll disconnect 21 too though.

Jake Thompson tries to explain that JP32 is not a "green PC button connection", but a "green PC LED connector". Both of these functions can validly be labelled "grnpc". He expects that the green PC button (that should put the PC to sleep) is to be connected to JP21, and a jumper on that connection would look like a permanently depressed sleep button, which could disturb normal system operation. Your old 486SX2 processor doesn't contain the advanced power management features (most notably the system management mode), whereas most 486DX4 processors do. A permanently pressed sleep button might be ignored on processors without power management features.

Oh my gosh I'm sorry I completely misunderstood. I was just thinking back to my previous manual lookthroughs that described that as an external battery jumper.

Really sorry guys.

mkarcher wrote on 2021-07-24, 21:47:

Charleston wrote on 2021-07-24, 21:38:

mkarcher wrote on 2021-07-24, 21:37:

If you happen to have a AMD DX4 with a "-NV8T" code on it, try getting that one to work first. The reason for recommending this kind of DX4 is that this processor doesn't support power management / SMI stuff (it is not SL-aware, as jakethompson1 says it), so if something is wrong with the "green" part of your mainboard, it won't affect the NV8T family of AMD DX4 processors.

Yeah my amd dx4 is a 8kb cache so I'll work on getting that one working and give up on the Intel for now.

Edit: it's sv8b not nv8t. Sorry

The SV8B is identical to the Intel DX4 in that regard: It has the CLKMUL signal on the same pin as the Intel processor (which could have been a problem with the NV8T), and it supports power management and L1 write-back just like the Intel processor. There is no obvious advantage of one processor over the other for getting your board running. You should be aware that AMD processors don't support x2.5 multipliers and just don't start. So don't bother trying any AMD DX4 or 5x86 at x2.5. This option is Intel exclusive.

Wow could jp 21 be the cause of all of this then? I feel like an absolute idiot.

Will update what happens when I get home I guess. I really appreciate all of your help and am crossing my fingers it's that stupid sleep mode.

If not I guess I'm whipping out the oscilloscope.