maxtherabbit wrote on 2022-03-28, 14:32:

Here is rev 2 of the interposer board. Designed my own circuit this time using a 7406 inverter IC instead of discreet transistors.

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This thread is awesome. Thanks to all who have contributed.

maxtherabbit - Could you post the components for the v2 design? Not sure what the sizes are.

Thanks

Resistors and caps are 0805 inductors are 1210 inverter is 14-SOIC

Built my interposer and I'm getting a keyboard lock error on boot and no ability to use the keyboard. Pin 34 has continuity to the keyboard lock pin on the motherboard. Tried driving it low and high to no effect. I have a "Regional HT6542" and there are no datasheets on it (I don't think this KBC is related to the Holtek HT6542B). I've also seen this motherboard (M396F V2.6) with VT82C42N, AMIKEY-2, etc. So I think it can handle any of those as well. So I dug up a VT82C42 datasheet, and it appears that in PS/2 mode, it uses Pin 25 for Keyboard Lock...

"However, if the VT82C42 is in Mouse LockTM mode (pin 25 on DIP40 or pin 28 on
PLCC44 parts connected to GND), the data from either keyboard or mouse will be prohibited from sending to
the host."

As luck would have it, Pin 25 on my motherboard is tied to GND. So I think that might be my problem. I've looked at other KBC datasheets, and it seems Pin 25 is typically NC. I'm going to try to cut the trace on the interposer and see if I can get past the locked keyboard.

VT82C42 datasheet attached. Let me know if I'm not reading it correctly, it's difficult to follow.

maxtherabbit wrote on 2023-08-18, 13:37:

Thank you, it appears pin 24 controls turbo on your board. In your first photo you can see the tiny trace jumpers (the little triangles) that select between pins 23, 24 and 27 with the one for pin 24 connected.

Unfortunately for you, all of those pins are required for the mouse so it's not as simple a matter as changing the jumper. What I would recommend is taking the mod board out and putting the original KBC back in the board. Then, with the system running at full speed, measure the logic level of pin 24. You can also use the keyboard shortcut to de-turbo the machine and verify that pin changed state as a sanity check.

Once you know whether we need to pull pin 24 high or low we can select an appropriate resistor value.

Finally managed to get around to this -- partly because I had no logic probe but also because the one I ordered had large clamps which I eventually replaced with Pomona mini clips when they finally arrived. Thanks for your prescribed diagnostic methodology. I tested thusly: With the board propped up in one hand and a momentary switch in the same hand, I probed pin 24 -- it has a default state of high with turbo on. For the sanity check, I kept the logic probe on the pin while I pressed the momentary switch. With the momentary switch pressed, the turbo LED turns off and the logic level switches to low.

It's a great board if not for this minor quibble, and I don't really need the turbo switching functionality (PS/2 is far more important). Would you kindly please advise on how to proceed with the resistor mod?

mockingbird wrote on 2023-10-25, 02:02:

maxtherabbit wrote on 2023-08-18, 13:37:

Thank you, it appears pin 24 controls turbo on your board. In your first photo you can see the tiny trace jumpers (the little triangles) that select between pins 23, 24 and 27 with the one for pin 24 connected.

Unfortunately for you, all of those pins are required for the mouse so it's not as simple a matter as changing the jumper. What I would recommend is taking the mod board out and putting the original KBC back in the board. Then, with the system running at full speed, measure the logic level of pin 24. You can also use the keyboard shortcut to de-turbo the machine and verify that pin changed state as a sanity check.

Once you know whether we need to pull pin 24 high or low we can select an appropriate resistor value.

Finally managed to get around to this -- partly because I had no logic probe but also because the one I ordered had large clamps which I eventually replaced with Pomona mini clips when they finally arrived. Thanks for your prescribed diagnostic methodology. I tested thusly: With the board propped up in one hand and a momentary switch in the same hand, I probed pin 24 -- it has a default state of high with turbo on. For the sanity check, I kept the logic probe on the pin while I pressed the momentary switch. With the momentary switch pressed, the turbo LED turns off and the logic level switches to low.

It's a great board if not for this minor quibble, and I don't really need the turbo switching functionality (PS/2 is far more important). Would you kindly please advise on how to proceed with the resistor mod?

ok sure one last measurement - with the machine powered off, and nothing inserted in the KBC socket please measure the resistance between pin 24 at the socket and ground

maxtherabbit wrote on 2023-10-25, 02:09:

ok sure one last measurement - with the machine powered off, and nothing inserted in the KBC socket please measure the resistance between pin 24 at the socket and ground

Thanks. I am getting almost precisely 6 MOhms (megaohms).

mockingbird wrote on 2023-10-25, 04:17:

maxtherabbit wrote on 2023-10-25, 02:09:

ok sure one last measurement - with the machine powered off, and nothing inserted in the KBC socket please measure the resistance between pin 24 at the socket and ground

Thanks. I am getting almost precisely 6 MOhms (megaohms).

hmm that's not quite what I was expecting, you were measuring at the motherboard without the interposer installed , correct?

how about checking it vs the 5V rail?

maxtherabbit wrote on 2023-10-25, 13:05:

hmm that's not quite what I was expecting, you were measuring at the motherboard without the interposer installed , correct?

how about checking it vs the 5V rail?

Let me re-do the measurements for you -- when you said 'nothing' in the socket, you meant without the interposer but I interpreted that to mean without anything at all. Without anything at all it's like before, as well as infinite resistance to 5v.

With only the KB controller IC installed, I get the following:

pin 24 to ground: 8.14 kOhm
pin 24 to Vcc: 6.27 kOhm

mockingbird wrote on 2023-10-25, 15:19:

Let me re-do the measurements for you -- when you said 'nothing' in the socket, you meant without the interposer but I interpret […]
Show full quote

maxtherabbit wrote on 2023-10-25, 13:05:

hmm that's not quite what I was expecting, you were measuring at the motherboard without the interposer installed , correct?

how about checking it vs the 5V rail?

Let me re-do the measurements for you -- when you said 'nothing' in the socket, you meant without the interposer but I interpreted that to mean without anything at all. Without anything at all it's like before, as well as infinite resistance to 5v.

With only the KB controller IC installed, I get the following:

pin 24 to ground: 8.14 kOhm
pin 24 to Vcc: 6.27 kOhm

You were right the first time, I meant nothing at all.

Ok so you can go ahead and solder a 2k resistor from pin 24 on the KBC socket to pin 40 (+5V) on the KBC socket (I'd recommend doing this on the underside of the motherboard) if you'd like, this will probably force turbo on.

To be 100% sure, the best test would be to install the KBC back in the socket (no interposer) and repeat the logic probe on pin 24 test but use the keyboard shortcuts NOT the button. (The shortcuts are CTRL+ALT+PLUS or CTRL+ALT+MINUS)

maxtherabbit wrote on 2023-10-25, 20:49:

You were right the first time, I meant nothing at all.

Ok so you can go ahead and solder a 2k resistor from pin 24 on the KBC socket to pin 40 (+5V) on the KBC socket (I'd recommend doing this on the underside of the motherboard) if you'd like, this will probably force turbo on.

To be 100% sure, the best test would be to install the KBC back in the socket (no interposer) and repeat the logic probe on pin 24 test but use the keyboard shortcuts NOT the button. (The shortcuts are CTRL+ALT+PLUS or CTRL+ALT+MINUS)

The closest I had to 2kOhms was 2.2K (it was either that or run two 1k parts in series), so I used that:

The CTRL+ALT+ combo didn't seem to work for this board, so I decided to just go for it:

Guess what? Not only does it work, BOTH turbo off and on work! I ran landmark 6 and tested with the turbo button to confirm the speed change.

Thanks very much! Perhaps a minor revision is in order for your next PCB to provide for a jumper that connects pin 24 to pin 40 for 386 motherboards that have a UMC chipset. I intend to test a different 386 UMC board as well as a 386 Opti board in the near future as well.

mockingbird wrote on 2023-10-26, 04:12:

Guess what? Not only does it work, BOTH turbo off and on work! I ran landmark 6 and tested with the turbo button to confirm the speed change.

Thanks very much! Perhaps a minor revision is in order for your next PCB to provide for a jumper that connects pin 24 to pin 40 for 386 motherboards that have a UMC chipset. I intend to test a different 386 UMC board as well as a 386 Opti board in the near future as well.

Glad to hear it.

As far as I can tell this is just a one off problem, and even if it were to come up again it might not be pin 24 it just as easily could be one of hte other three. Turbo implementation was unique to each individual motherboard, not chipset specific, so I don't think a PCB revision is practical here.

I have another board I want to report on:

ECS UM4980

Result: Does not work. With the interposer plugged in, the keyboard is not detected. The motherboard has a jumper (JP3) to switch between the internal (UM8496F) or an optional external KBC. I confirmed that an external KBC worked without the interposer.

EDIT (03/22/2024): Working now, thanks to Paar. See this thread.

mockingbird, which keyboard controller are you using? I've setup quite a few systems with my own adaptor and haven't run into so many troubles that you have.

I have had one board in which I ran into the situation where the de-turbo wasn't working, but I wasn't bothered all that much and ultimately wired the de-turbo switch to a much lower FSB - I think 20 MHz vs. 40 MHz. To go slower, I could also use software to reduce the multiplier. Maybe one day I'll look into this further as you've done.

For the other situation in which the KBC adaptor didn't work at all, I have found that sometimes swapping the keyboard controller for another model that also supports PS/2 mice functionality was sufficient. The most common KBC options I've used are:

Holtek HT6542B
AMIKEY-2
VIA VT82C42N

Assuming you have set the PS/2 mouse bit in the AWARD BIOS using Modbin, have modified an AMI BIOS manually, or are using ps2suppc, try rotating between these 3 KBCs.

feipoa wrote on 2023-10-27, 16:26:

mockingbird, which keyboard controller are you using? I've setup quite a few systems with my own adaptor and haven't run into so many troubles that you have.

Thanks, I will try the Mega "F" controller in the ECS motherboard -- that's a good suggestion. I didn't think that could be it because the VIA chip seemed to work without the interposer (or perhaps the motherboard could just be ignoring the jumper for the external KBC and using the internal one), but it's worth a shot.

Does the Mega-F support ps/2?

Of the 3 options mentioned above, I’ve had the least luck with the VIA, which is unfortunate because it seems to be the most plentiful.

feipoa wrote on 2023-10-27, 17:07:

Does the Mega-F support ps/2?

iOS the 3 options mentioned above, I’ve had the least luck with the VIA, which is unfortunate because it seems to be the most plentiful.

So far I'm 1/1 with the VIA - I have two more boards I need to test and I'll be sure to post the result... Oh - I need to mention this too: With the UM4980, there's no power at all going to the keyboard with the interposer connected. Maybe that info helps in diagnosing this? Oh, and, same thing with the Mega F. Yup - it does support PS/2 - I put one in my Shuttle HOT-433.

feipoa wrote on 2023-10-27, 17:07:

Does the Mega-F support ps/2?

Of the 3 options mentioned above, I’ve had the least luck with the VIA, which is unfortunate because it seems to be the most plentiful.

Yes. Agree on the VIA

keropi wrote on 2018-04-18, 07:55:

I mentioned this in a previous post: I soldered a brand new controller (new via kbc, new pcb, new components) but it did not hel […]
Show full quote

I mentioned this in a previous post: I soldered a brand new controller (new via kbc, new pcb, new components) but it did not help.
But it seems the kbc wasn't the issue at all , since I have edited my last post some times this is what I found so far:

- the tsr does not work if you don't solder a ps/2 port and have a mouse connected
- using a 5422 or 5429 cirus isa vga makes the tsr to complain that there is no mouse and it locks keyboard input after exiting making a reboot necessary

I'm having the exact same issue with a Cirrus 5434 (SpeedStar 64) and ps2suppc.com. It works perfectly fine with my AHEAD vga card. Anyone have any luck solving this? The SpeedStar64 doesn't even have an electrical connection to IRQ12 on the ISA slot. So, something else must be going on.

ahyeadude wrote on 2023-10-04, 02:51:

Built my interposer and I'm getting a keyboard lock error on boot and no ability to use the keyboard. Pin 34 has continuity to t […]
Show full quote

Built my interposer and I'm getting a keyboard lock error on boot and no ability to use the keyboard. Pin 34 has continuity to the keyboard lock pin on the motherboard. Tried driving it low and high to no effect. I have a "Regional HT6542" and there are no datasheets on it (I don't think this KBC is related to the Holtek HT6542B). I've also seen this motherboard (M396F V2.6) with VT82C42N, AMIKEY-2, etc. So I think it can handle any of those as well. So I dug up a VT82C42 datasheet, and it appears that in PS/2 mode, it uses Pin 25 for Keyboard Lock...

"However, if the VT82C42 is in Mouse LockTM mode (pin 25 on DIP40 or pin 28 on
PLCC44 parts connected to GND), the data from either keyboard or mouse will be prohibited from sending to
the host."

As luck would have it, Pin 25 on my motherboard is tied to GND. So I think that might be my problem. I've looked at other KBC datasheets, and it seems Pin 25 is typically NC. I'm going to try to cut the trace on the interposer and see if I can get past the locked keyboard.

VT82C42 datasheet attached. Let me know if I'm not reading it correctly, it's difficult to follow.

VT82C42.PDF

To close this loop. I gave up on this particular 386sx motherboard and am using another. The interposer works fine, but just have problems with using ps2suppc.com and the 5434 as referenced above.

ahyeadude wrote on 2023-10-27, 19:21:

To close this loop. I gave up on this particular 386sx motherboard and am using another. The interposer works fine, but just have problems with using ps2suppc.com and the 5434 as referenced above.

I am building a GD5434 ISA and will report back if I have this issue with my 386. I flashed it to Mr. BIOS, so I don't need ps2suppc, but nevertheless.