generally all of the AMI labeled ones are interchangeable, go with rev F or later if you want ps/2 support

maxtherabbit wrote on 2025-06-10, 11:48:

generally all of the AMI labeled ones are interchangeable, go with rev F or later if you want ps/2 support

I can't find any MEGATRENDS MEGA-KB-H-WP or MEGATRENDS MEGA-KB-F-WP chips that I can order at reasonable price. I found VIA VT82C42N chip that I can order, but I'm not sure if it's 100% compatible with these MEGATRENDS MEGA-KB-F/H-WP chips.

And what about the other one for the 386SX motherboard? Here's the picture of the original KB-controller for KMX-AL25/33SX board:

Ok, on TRW site there are two pictures of FIC 486-GVT-2 motherboards with VIA VT82C42N KB-controller, so it must be compatible with MEGATRENDS MEGA-KB-H-WP chip. I ordered two of these VT82C42N chips (the cheapest offer on alibaba-and-the-40-thieves was for 2 pieces bundled) for about EUR 4 including shipment. I need only one of these for FIC 486-GVT-2 motherboard, but I have no idea if the second VT82C42N chip can be used as replacement for the faulty KB-controller (with the sticker "(C) 1988-1990 AMI KEYBOARD") on the 386SX board.

Winbond W83C42 are also replaceable with the AMI keyboard controllers, pin for pin, but require a 7407 (SN7407N) instead of a 74F04 or similar near the KB controller.

They're fast like the VT82C42N, which also require a 7406/7407... If on bootup it says Keyboard error, it's most likely these chips that need changing.

MikeSG wrote on 2025-06-11, 15:36:

Winbond W83C42 are also replaceable with the AMI keyboard controllers, pin for pin, but require a 7407 (SN7407N) instead of a 74F04 or similar near the KB controller.

They're fast like the VT82C42N, which also require a 7406/7407... If on bootup it says Keyboard error, it's most likely these chips that need changing.

Thanks for the input, MikeSG. It seems like that these AMI W83C42 controllers will not work on most of the old 386-boards.

I checked my 386-board with the damaged Award KB-controller and under its KB-controller's chip (inside its 40-pin socket) there are 74F00N and 74F32N and-nand-or-...-whatever-gate chips. The other connected to KB-controller socket pins nearby 74-xx chip is 7406N inverter/buffer (this one should be faster than 74F04, right?). Not a 7407, but maybe it should work with a newer KB-controller...

I will found out if the VIA VT82C42N controller will be as picky as Winbond's W83C42, when I got the package from China.

Still I'm open for KB-controllers replacement suggestions.

I ordered VIA VT82C42N, but came VIA-II VT82C42N.

Is there any actual difference between these or "VIA-II" is just a stupid relabeling for later production of VIA VT82C42N chips?

I believe it's the same chip.

If using/testing a Winbond 83C42, the 7406N chip needs to be changed to a 7407.

The Winbond 83C42 works on a 386. I used it to replace an AMI controller when I was overclocking a 386sx a little while ago.

There is another type of keyboard controller available but I can't remember the name of it. If you look at 486-era boards, many of those keyboard controllers are still made today... But require the same 7406 or 7407 buffer chip. Some have PS/2 mouse support - not sure if that gets in the way. The Winbond doesn't.

Thanks for the reply, MikeSG.

MikeSG wrote on 2025-07-12, 08:54:

I believe it's the same chip.

I thought so, but: Re: Problems with semi-alive FIC 486-GVT-2 motherboard hanging ar POST code "05"

MikeSG wrote on 2025-07-12, 08:54:

If using/testing a Winbond 83C42, the 7406N chip needs to be changed to a 7407.

The Winbond 83C42 works on a 386. I used it to replace an AMI controller when I was overclocking a 386sx a little while ago.

There is another type of keyboard controller available but I can't remember the name of it. If you look at 486-era boards, many of those keyboard controllers are still made today... But require the same 7406 or 7407 buffer chip. Some have PS/2 mouse support - not sure if that gets in the way. The Winbond doesn't.

Good to know all of this. And now I see, that these VIA-II VT82C42N chips are not suitable as replacements in both my cases - for the 386 board and for the semi-dead/half-alive First-place International Complications 486-GVT-2 board 🙁

P.S. There are other KB-controller models like AMIKEY, AMIKEY-2, JETKEY, LT38C41... and all these chips are in one common "MCS-48" microcontroller family, but I know nothing about them.