Never found the Pin out on a "AMIKEY-2" painted KBC (because AMI did not make the controller, they only programmed it and whoever made it allowed it silkscreened that way AFAIK, same with nearly all BIOS chips with AMI stickers). Basically all old KBC are "Peripheral Controllers" with the eprom flashed with what routine is desired, most with keyboard routine.
Have found a Fujitsu and Holtek with "AMIkey-2" stickers but nearly all 40 Pin Keyboard controllers are based on Intel 8042 or 8247.
I suggest you check the Holtek 6542B datasheet as it (like Intel 8247) are PS2 compatible and are pin-for-pin compatible with nearly all 40 pin KBC and has a sample schematic (the one I have does).
edit: tried to fix mt crappy post. am sure someone else can give more info....

Horun wrote on 2022-08-10, 02:55:

I suggest you check the Holtek 6542B datasheet as it (like Intel 8247) are PS2 compatible and are pin-for-pin compatible with nearly all 40 pin KBC and has a sample schematic (the one I have does).

Thank you, that is extremely helpful. I am pouring over the datasheet now.

Can these various 8042 derivatives that are pin-compatible be swapped for each other? Or should I be on the lookout for another AMIKEY-2 chip?

Pinouts are nearly always same but there can be software differences that some BIOSes may rely on.

https://alexandrugroza.ro/microelectronics/sy … sbmc/index.html search "AMI"
https://alexandrugroza.ro/microelectronics/es … bios/index.html

Anyone know if Amikey 2 (RAMIF-0016) is reprogrammable? I keep finding references saying it's programmable, but not clear if that's only factory programmed.

I replaced a bad one recently. It was recognizing key presses to enter the BIOS and cancel the memory test, but stops responding after. Before replacing it, it wasn't completely clear what was broken, but I took the leap to unsolder the old chip and solder a socket.

I'd like to reprogram the broken one if possible. But I can't even find any similar chip that's known to be reprogrammable in a XGecu T48. I looked at the HT6542B datasheet, but that doesn't seem programmable, nor does it appear in the list of supported chips of any programmer.

The programmability likely refers to One Time Programmable factor if they are not mask-ROM based. Volume products like these are pretty much always mask-ROM based since it just costs less that way and won't require a programming step which is often manual effort.

OK, that's fine if they're not reprogrammable. I want to know more why it stopped working. Do OTP and mask ROMs degrade over time or is it something else?

Does the replacement work ok?
One possibility is esd degrading input pin buffer, but that wouldnt explain letting you enter BIOS, unless its press any key to enter bios and its receiving garbage key readings.

spacesaver wrote on 2023-09-20, 05:13:

OK, that's fine if they're not reprogrammable. I want to know more why it stopped working. Do OTP and mask ROMs degrade over time or is it something else?

Mask ROMs are essentially forever, but OTP EPROM, like any EPROM and other trapped charges based storage methods, will suffer bit rot as the charge leaks out the cells.
rasz_pl's idea about why is most probable. Keyboard and mouse ports are open to the hostilities of external world and it is not impossible that wearing the wrong clothes and plugging stuff in there could have been what ended up causing the problem.

It was only recognizing the delete key needed to get into the bios, not just any key.

Does the replacement work ok?

Yes, I said desoldering the chip (easy with hot air) and painstakingly soldering each of 40 pins (couldn't use hot air because the plastic socket would soften and make the pins slide out) was a huge gamble, but paid off 😀

Wow, I didn't realize OTP EPROM meant the UV erasable kind. Haven't seen that since a high school electronics class.
I was trying to use a USB <--> PS/2 keyboard adapter that rasz referred me to. https://github.com/No0ne/ps2x2pico. That had exposed solder joints for the data and clock lines, so it's almost certain I touched those lines, so ESD could be possible. But I wasn't using it when it failed. I couldn't get it to work, so just got a PS/2 keyboard.

has anyone thought to make a modern replacement with something like a pi pico?

Tiido wrote on 2023-09-20, 12:48:

Mask ROMs are essentially forever, but OTP EPROM, like any EPROM and other trapped charges based storage methods, will suffer bit rot as the charge leaks out the cells.

Some OTP EPROM families are done with fuse arrays instead trapped charges (them don't have the quartz eye). These will also last forever.

From what I have understood, (anti)fuse based devices are referred to as just PROM and they seem to have gone out of fashion not long after EPROMs became a thing and did not seem to reach any higher densities of EPROMs, probably because it is difficult to blow a bit and not affect the neighbors with the fallout. But yeah, they last forever too.

Have you tried some other keyboard controller?
If I am not wrong your board is an Asus.

Horun wrote on 2022-08-10, 02:55:

Never found the Pin out on a "AMIKEY-2" painted KBC (because AMI did not make the controller, they only programmed it and whoeve […]
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Never found the Pin out on a "AMIKEY-2" painted KBC (because AMI did not make the controller, they only programmed it and whoever made it allowed it silkscreened that way AFAIK, same with nearly all BIOS chips with AMI stickers). Basically all old KBC are "Peripheral Controllers" with the eprom flashed with what routine is desired, most with keyboard routine.
Have found a Fujitsu and Holtek with "AMIkey-2" stickers but nearly all 40 Pin Keyboard controllers are based on Intel 8042 or 8247.
I suggest you check the Holtek 6542B datasheet as it (like Intel 8247) are PS2 compatible and are pin-for-pin compatible with nearly all 40 pin KBC and has a sample schematic (the one I have does).
edit: tried to fix mt crappy post. am sure someone else can give more info....

Only exception I know of this is the are the VIA controllers. VIA KBC are not programmed microcontrollers. They are implemented 100% in logic. This is mentioned in the datasheet.

Tiido wrote on 2023-09-20, 12:48:

Mask ROMs are essentially forever, but OTP EPROM, like any EPROM and other trapped charges based storage methods, will suffer bit rot as the charge leaks out the cells.

It's OTP ROM. OTP for One Time Programmable and ROM for Read Only Memory. EPROM is Erasable Programmable ROM. OTP EPROM would be a contradiction. EPROM are UV erasable, EEPROM are electrically erasable.

debs3759 wrote on 2024-03-16, 04:58:

It's OTP ROM. OTP for One Time Programmable and ROM for Read Only Memory. EPROM is Erasable Programmable ROM. OTP EPROM would be a contradiction. EPROM are UV erasable, EEPROM are electrically erasable.

While the term is confusing, there are EPROM dies packaged in a cheap plastic case without a window, so there is no (easy) way to erase them. To differentiate them from fuse-base or antifuse-based OTP ROMs, it is common to call the one-time programmable chips based on EPROM technology "OTP EPROM". Atmel for example uses the term. Someone at the company noticed the issue issue with "one time programmable ersable..." and expands the acronym as "One-time programmable electrically programmable read-only memory". As all other programmable ROM chips (so everything except mask ROMs) is electrically programmed, this term doesn't make much sense, too - but at least it does not contain the contradiction you mention.

Jaa, there is some confusion on this part.

In any case, vast majority of OTP chips you find are actually EPROMs without a window, they are not true ROMs and will bit rot sooner or later. True OTP ROMs based on (anti)fuse etc. tech are ancient and you are pretty much never going to encounter one in this hobby. By the time we had 2KB sized EPROMs, true PROMs were already going extinct. It is rare to encounter even a 27x16, much less same or even smaller sized PROM chip.