Error 301 -> Keyboard error.

Maybe your PC is trying to initialize your keyboard in an unexpected way. Keep in mind that XT and AT keyboards are different, and some AT keyboards won't support XT protocols.

OK, but I can press F1 key and boot the os and I can interacting with PC. The keyboard seems to be XT because there aren't windows keys and the connector is old DIN.

If you access the BIOS there might be an option to skip the keyboard error check. It doesn't really solve the issue, but at least prevents it from coming up and requiring you to do anything.

Again, that assumes there is an option to disable the keyboard error.

Maybe a good idea but I don't know how to access on the BIOS. At power on there isn't any reference 🙁

Well the usual keys to try are DEL, F1, F10, F2

There is another way I used to access the bios way back when. If I didn't know how to access the BIOS on a PC, I found that in most of them, you could just press a bunch of keys on the keyboard all at once to cause the keyboard buffer error. At that point, the system would usually give you an option to press a key to continue or another key to access setup. The one you wanted was the key to access the setup. From there I could make the changes I needed.

yes it isn't elegant but simply pressing my hand on a bunch of keys while I powered it on worked on many occasions for me!! 🤣

XT-class machines don't have a BIOS normally. They are set up using dip switches or jumpers.

mjnman wrote:

OK, but I can press F1 key and boot the os and I can interacting with PC.

Maybe the keyboard is initializing properly, but it gives a response that the motherboard doesn't understand (or don't give a response in time). I have a ZX Uno (a FPGA based sytem that can be configured to run as various systems), and some "cores" (=systems emulated) had various problems due to bad initializations (i.e.: keyboards that works at power up but fails when rebooting, keyboard that only works after reset or keyboards that don't work at all).

mjnman wrote:

The keyboard seems to be XT because there aren't windows keys and the connector is old DIN.

PS/2 connectors (=mini DIN) were used at first on PS/2 systems (surprise!), but they weren't common in other PCs until Pentium age. Most 286, 386 and 486 systems have DIN conectors... so many AT keyboards were built with DIN plugs.

derSammler wrote:

XT-class machines don't have a BIOS normally. They are set up using dip switches or jumpers.

Well that explains it then! My first PC was a 286. My aunt owned an older XT but I never had to use it much bitd. We also used them in high school when I was learning data processing, but again from a technical perspective we never had to touch them other than to turn them on and boot from the right disk.

As you state that the keyboard is functional and you're able to boot the OS etc - is the keyboard perhaps an auto-sensing one, where it can automatically detect and work on both XT & AT class computers? If that's the case, then maybe it is defaulting to AT mode and not switching to XT mode in time for when the BIOS initially checks it. Would possibly explain why a reset clears the error, as the keyboard would already be initialised in XT mode.

Not sure if there's much way around it, though you could try switching to a different BIOS, ie. the Turbo XT BIOS. That would require replacing & programming new EPROM or EEPROM chips though.

It is possible to use modern 1 or 2 Mbit flash EEPROMs in older boards via a simple adaptor. All that need is a DIP-32 socket, one wire and soldering skills. The EEPROM can be flashed on any modern (Socket5...462 era) motherboard using hot-swap. Instructions can be googled.

But a better way is to find a better keyboard with mechanical AT/XT switch or even an old XT Keyboard.

Thank you for the many answer. At this point I think the problem is the keyboard how explained from @PTherapist. I'll try to search a pure XT keyboard.
thank you very much

derSammler wrote:

XT-class machines don't have a BIOS normally. They are set up using dip switches or jumpers.

To be exact, they do not have a CMOS setup in their BIOS.
The BIOS is the Basic Input/Output System, which is more or less the 'firmware' that boots the PC. Every PC has that.
When the AT was introduced, they started using a Motorola MC146818 real-time clock and timer. This contains some battery-powered CMOS memory, which IBM used to store configuration info. IBM still used a separate setup application supplied on floppy, to configure the AT's CMOS, but clones quickly started putting the setup into the BIOS itself, which became the famous "Press DEL/<whatever key> to enter CMOS setup" on boot.