I admire your persistance to repair that board. Have you checked power supply pins? Pins 1 and 9 should be 3.3V and pins 25 and 38 should be 3.3V or maybe even 5V according to the datasheet.

The ground is common (reference) to all signals so it is normal to show continuity across the board, if there are resistors between plugs and signal pins it is normal not to hear beep since most multimeters beep if resistance is below 50 ohms, you can try on 200 ohm, 2k or 20k scale to see what is …

It's not uncommon for that chip to fail in such a way that on software side everything works fine while there is no analog output. The chip has integrated headphones amplifier whose output is often used by the motherboard and traced to the green plug. In that case there is nothing you can do except …

Power C 2.2.0 also doesn't contain cwindows.h. It's probably added third party library of some kind. I guess the project uses text mode so with functions mentioned above it is easier to manipulate the screen.

Usually COM port 1 uses IRQ4 and COM port 2 uses IRQ3 while LPT port uses IRQ5 or IRQ7. If there is no need for parallel and game port maybe it's good idea disabling them to avoid conflict with the sound card.

Few decades passed and I still have a DOS/WIndows98SE machine with DOS MAME on it. It's a Chaintech 7AJA2 AMD socket 462 board with Athlon 2400+, the board has one ISA slot suitable for sound cards and CMI8738 onboard. If I remember correctly I found that it works best when running on Windows 98SE …

I have a total of 12 286 boards and statistics are that most of them are PLCC soledered or PLCC in socket, only one LCC and I have none of the PGA.

Hi, Is the FPU running at 2/3 or 3/2 ? Afaik, the 2/3 thing was only true for the original 287 from intel (pre-XL). You can choose between onboard 32MHz (16MHz clock) oscillator which in fact is 2/3 of the CPU's 50MHz (25MHz clock). The other option is custom oscillator via socket on the board for …

Another update. Keyboard problem solved. It is a "software" problem, in the BIOS setup option "Turbo switch function" must be disabled. Strange but it solves the problem and the keyboard works normaly. Another interesting thing is that option does not disable turbo switch for real, hardware switch …

I guess she is now vintage also... 😉

Well, I must admit that I can't delay buying a freqmeter and/or logic analizer anymore ;) In the meanwhile I traced the PCB which confirmed what I thought earlier. Third crystal (32MHz) is traced to the JP3 which selects between that crystal and the one in the Y4 thus selecting the frequency for 287 …

When I remove the JP4 everything works the same but there are endless short beeps comming out of the speaker (very anoying). Nothing to do with the keyboard fail. It's interesting that while in setup/diags of the BIOS, keyboard can work for hours but when OS stars to boot it stops immediately ( …

25MHz 287s don't exist, so unless you're OK with overclocking the one that you have, you will need to plug in a suitable oscillator for your 287. I am well aware of that fact, my IIT is rated 20MHz so maybe it can pull it out on 25. Still I have a dillema. There are three crystals on board: one …

OK, here is the update, after I programmed EPROM with 2hlm004.bin 64kB file the board woke up, memory test passed, got to the point of OS loader. The only thing suspicios is the speaker which beeps short beeps repedeately. Still there are mystery jumper settings that I'm worried about, and about …

Thanks for quick help there. First of all AMI chip is keyboard bios only, the board needs EPROM for SYSTEM BIOS which is a totaly different thing. But I think it would not be a problem, I have a bunch of good EPROM chips and a good EPROM programmer and even the file that I found is one file instead …

In Yugoslavia Novkabel launched in 1985 a ET188A PC-XT compatible machine based on a 80188 CPU. Machine was fully compatible with PC-XT clones with MS-DOS or CP/M. They chose 188 cpu because it had integrated peripherals so design of the motherboard was easier. Technical Specifications: CPU: Intel …

Found this board in my basement few days ago. Seemed interesting 8 simm sockets, 25Mhz cpu, I have a nice working ITT 287 for it etc. The board says MG PRODUCT MG-2862002 REV. 1.2 After brief inspection I figured out that some parts are missing, BIOS ROM, jumpers, maybe something else I don't know. …

Great thread! Few years ago I tried to fill the gaps in my collection but I couldn't find all of the old SDKs. I see now that I was not alone in this. Thanks for sharing these files. By the way I'm looking for the dxsdk_sum2004_symbols.exe . Actualy any of the symbols collection from 2004 or 2005 …