Having to hand cut and fit all the male pins to the PCB is miserably tedious but I couldn't find a better option

maxtherabbit wrote on 2025-03-01, 01:23:

Having to hand cut and fit all the male pins to the PCB is miserably tedious but I couldn't find a better option

ya, it will be unpleasant. I'm just going to do it on one module; the floater. The other 9 units will get the Arduino flat pins, which are a breeze.

If anyone has a part number for a DIP-40 KBC socket with a cross-member, could you relay it here? Recently ordered, in-hand parts only please. Many thanks.

With some stubborn determination, I was able to remove DIP pins from sockets, trimmed them, then re-purposed as the KBC-PS2 pins. I wouldn't do it again. Unfortunately, the pins from DIP IC's, which are of the ideal thickness (0.25 mm), aren't quite long enough to re-purpose. The DIP socket pins are the perfect length when trimmed, but are on the thinner side at 0.16 mm.

Shown using my last unused DIP-40 socket with a cross-member.

Some photos provided...

A few more to wrap it up...

I assembled about a dozen of these modules and was doing some testing. I noticed that some keyboard controller chips get quite a bit hotter than others.

Intel / American Megatrends / AMI KB-BIOS-VER-F = 44.3 C
Intel / American Megatrends / MEGA-KB-F-WP = 44.3 C
Intel / Megatrends Megakey = 42.3 C

Holtek HT6542B = 28.8 C
VIA V T82C42N = 29.1 C

This may or may not cause issues for some users who are pushing the overclocking limits of their system. On my testbed, which has lousy AT connector contacts, and has the KBC placed right next to the AT connector, these hot KBC's were causing some drop in the 5 V rail. I think it was around 0.08 V, but enough so that I couldn't run my SXL2 at the desired voltage (crashes). The issue noted here is minimal, but I recall another user mentioning that certain KBC's worked better than others when pushing the system to its limits.

My preferred all around keyboard controller is the Holtek HT6542B, but I some of the "hot" keyboard controllers may be needed to get soft reset working on some systems.

feipoa wrote on 2025-03-05, 11:32:

I assembled about a dozen of these modules and was doing some testing.

Does your board have pin-26 tied to Vcc? I found that HT6542B isn't being initialized properly without it (at least on my board). Some other controllers like VT82C42N or AMIKEY-2 work fine without it.
Or you rely on this connection already present on the motherboard?

For my KBC-PS2 prototypes and for Max's derivative PCBs, Pin 26 is simply passed through, meaning if the motherboard has pin 26 connected to Vcc, then so will the adaptor and keyboard controller chip.

As I will soon be upgrading all my floating 286/386 motherboards with the KBC-PS2 mod, I will be sure to check how pin 26 is connected on the motherboard. Are you suggesting that it is preferred to have the KBC-PS2 PCB wire pin 26 directly to VCC, just in case the motherboard doesn't have this connection already?

feipoa wrote on 2025-03-06, 03:53:

Are you suggesting that it is preferred to have the KBC-PS2 PCB wire pin 26 directly to VCC, just in case the motherboard doesn't have this connection already?

Pin-26 is a GPIO pin. Generally it isn't a good idea to connect pins directly to +5V. However it's acceptable in some cases.
As you don't know for sure what current can be sunk by any random KBC you use it's better to add a 10..56k resistor in series.
I'd avoid lower values 'cause resistor on MB is in parallel to your one. As well as higher values 'cause you can encounter interference.

froller wrote on 2025-03-06, 10:39:

Pin-26 is a GPIO pin. Generally it isn't a good idea to connect pins directly to +5V. However it's acceptable in some cases. As […]
Show full quote

feipoa wrote on 2025-03-06, 03:53:

Are you suggesting that it is preferred to have the KBC-PS2 PCB wire pin 26 directly to VCC, just in case the motherboard doesn't have this connection already?

Pin-26 is a GPIO pin. Generally it isn't a good idea to connect pins directly to +5V. However it's acceptable in some cases.
As you don't know for sure what current can be sunk by any random KBC you use it's better to add a 10..56k resistor in series.
I'd avoid lower values 'cause resistor on MB is in parallel to your one. As well as higher values 'cause you can encounter interference.

I'll keep it in mind as I go through my boards. I have modified about a dozen boards to date, but haven't had any issues related to pin 26's voltage. I have run into issues in which certain motherboards heavily prefer certain KBC's. For example, yesterday I was modifying my Chaintech 340SCD, which is a SiS Rabbit based 386 motherboard, and with the VIA VT82C42N installed, nothing shows on the display screen and the PC speaker beeps. With the Holtek HT6542B installed, everything works fine. Today, I'm working on a Daewood AL486V-D and it, too, won't turn on with the VIA controller installed, but it runs an Intel Megakey just fine.

feipoa wrote on 2025-03-11, 05:38:

I have run into issues in which certain motherboards heavily prefer certain KBC's.

Older boards with no dedicated multi controller used to use KBC also for generating Reset, A20 Gate signals, sometimes for Turbo and may be some other functions. So not all of them are configured to do all the stuff board awaits from them.
As far as I understood all these KBCs generally are factory programmed 8051 micro-controllers. So you never know what else it can do besides KB, MS, A20 and RST unless you get the datasheet.

VT82C42 datasheet requires pins 5 (TH_SS), 25 (TH_PROG) and 26 (TH_SSPP) to be tied high and pin 7 (TL_EA) to be tied low for normal operation.
HT6542B datasheet requires pin 26 (TEST) to be tied high, pins 5, 7 and 25 are not connected (or simply not used and configured as inputs or Hi-Z).

I'd recommend to check pins 29-32 (GPIO) as all of them can be configured for either input or output and affect KBC as well as MB. And also pin 33 (GPIN) that can affect KBC behavior.
This may cue you on why some KBCs work and some don't.

UPD I also found another DIP-40 KBC datasheet. Take a look at pin description. It clarifies some functions of KBCs on MBs of those days.

That you for the additional information. I normally don't get into much detail unless I need to, but such a time may eventually arise. I have too many other tasks which I want to get to while I still have the energy.

The most common KBC issues I've come across were:

1) keyboard controller causes system not to turn on
2) system turns on, but beeps
3) pressing the turbo button causes a hung system
a) always
b) only with a 386 in 2x mode
4) soft-reset not working
5) A20 handler error from HIMEM
6) Fast Gate A20 BIOS function not working

I've found that some motherboards, even when using the original keyboard controller in non-PS/2 mode, may hang with turbo button use. This was the case with my Daewoo AL486V-D.

So far, swapping around the keyboard controller models resolves the issues. If someone doesn't have a variety of controllers to swap around, I can see how digging into the pins, as you've done, would be helpful.

The VIA VT82C42 has been my worst performer, so I normally start testing with the VIA in hope that it works. If it does work, I can save the rarer controllers for other, more fussy, motherboards. This has been my plan of attack. I still have about a half dozen motherboards to upgrade. I will probably tack on the HOT-433 as well, considering that someone else has already done the leg work.

feipoa wrote on 2025-03-12, 00:30:

1) keyboard controller causes system not to turn on 2) system turns on, but beeps 3) pressing the turbo button causes a hung sys […]
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1) keyboard controller causes system not to turn on
2) system turns on, but beeps
3) pressing the turbo button causes a hung system
a) always
b) only with a 386 in 2x mode
4) soft-reset not working
5) A20 handler error from HIMEM
6) Fast Gate A20 BIOS function not working

1) Check the RESET line (i.e. ISA slot pin B2) if it stuck high. Possibly wrong pinout.
2) dunno, may be can't initialize KBC. Check POST codes.
3) Looks like Turbo is wired via KBC (my LS486e also freezes with Turbo off... I have to think 'bout it)
4) What does "soft-reset" means? Writing 2 bytes to IO port to drop NRST line on the MB? But this is identical to hw reset.
5) Certainly a KBC issue. However VT82C42 and HT6542B both can control A20 gate. Possibly wrong pinout.
6) same as above

Thanks.

"soft-reset" is to restart the computer by pressing these keyboard keys simultaneously: Ctrl-Alt-Del

feipoa wrote on 2025-03-12, 04:38:

"soft-reset" is to restart the computer by pressing these keyboard keys simultaneously: Ctrl-Alt-Del

This is exact equivalent to INT 19h. BIOS is responsible for this operation. It doesn't involve hardware at all. It just JMP to the beginning of OS loading procedure. So RESET signal is not involved in soft restart.

froller wrote on 2025-03-12, 09:39:

feipoa wrote on 2025-03-12, 04:38:

"soft-reset" is to restart the computer by pressing these keyboard keys simultaneously: Ctrl-Alt-Del

This is exact equivalent to INT 19h. BIOS is responsible for this operation. It doesn't involve hardware at all. It just JMP to the beginning of OS loading procedure. So RESET signal is not involved in soft restart.

Whatever the actual reason is, I didn't look into, but swapping the KBC for a different brand resolved the issue.

froller wrote on 2025-03-12, 09:39:

feipoa wrote on 2025-03-12, 04:38:

"soft-reset" is to restart the computer by pressing these keyboard keys simultaneously: Ctrl-Alt-Del

This is exact equivalent to INT 19h. BIOS is responsible for this operation. It doesn't involve hardware at all. It just JMP to the beginning of OS loading procedure. So RESET signal is not involved in soft restart.

yeah but the KBC has to call the warm boot vector when it detects the three finger salute

I've read thoroughly datasheets for KBD42W11, KBD43W13, W83C43, HT6542B and VT82C42 and combined all the pin information into single document.
Hopefully it helps you to investigate KBC incompatibilities. At least it shows some functions of KBC other than keyboard and mouse interaction.
The only thing I haven't yet figured out is what is "Manufacturing jumper" connected to Pin32.
Also take a look a pins 27-30. They are have no special purpose according to datasheet but still can be controlled with status registers of KBC. Thus they can be used for some undocumented purposes.
They also can be used in your adapter board if you need some kind of program configuration.

maxtherabbit wrote on 2025-03-12, 13:22:

yeah but the KBC has to call the warm boot vector when it detects the three finger salute

And it does this w/o pulling Pin4 low. Otherwise it will be a cold restart and POST will be performed. And it's known that "three finger salute" bypasses POST.

froller wrote on 2025-03-06, 10:39:

Pin-26 is a GPIO pin. Generally it isn't a good idea to connect pins directly to +5V. However it's acceptable in some cases. As […]
Show full quote

feipoa wrote on 2025-03-06, 03:53:

Are you suggesting that it is preferred to have the KBC-PS2 PCB wire pin 26 directly to VCC, just in case the motherboard doesn't have this connection already?

Pin-26 is a GPIO pin. Generally it isn't a good idea to connect pins directly to +5V. However it's acceptable in some cases.
As you don't know for sure what current can be sunk by any random KBC you use it's better to add a 10..56k resistor in series.
I'd avoid lower values 'cause resistor on MB is in parallel to your one. As well as higher values 'cause you can encounter interference.

Disregard this. Pin-26 should be connected directly to +5V.

feipoa wrote on 2025-03-01, 01:31:

If anyone has a part number for a DIP-40 KBC socket with a cross-member, could you relay it here? Recently ordered, in-hand parts only please. Many thanks.

I recently put in a general digikey order and wanted to point out that this DIP40 KBC socket has a cross-member:
1-2199299-5
https://www.digikey.ca/en/products/detail/te- … 99299-5/5022052
These are more expensive than the open sockets I ordered previously.