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Re: Original IBM EGA card repair thread

Posted on Yesterday, 19:31

That's exactly what is happening. 8 bit ethernet cards would often allow you to set the UMA window for the onboard boot ROM to anywhere in the upper address space (including C000 which is where all video option ROMs live) since they expected to be used along side MDA/CGA cards with no video BIOS …

Re: Original IBM EGA card repair thread

Posted on 2023-06-02, 20:53

Possibly, yes. The network card also has a BIOS ROM on it. Maybe that is conflicting. I have to wait until next week to work on the 5150 more, though, since I have some parts coming in the mail for it. My previous post was unclear. Here are the failure states so far: 1. IBM EGA or clone EGA inserted …

Re: Original IBM EGA card repair thread

Posted on 2023-06-02, 20:19

More progress. The 5150 produces the one long + two short beeps with both the IBM EGA card and a different, known working clone EGA card. When I remove my network card (a Racal Interlan NI5210C-10BT), the system boots and displays video with both EGA cards. That network card is not configured to …

Re: Original IBM EGA card repair thread

Posted on 2023-06-02, 19:15

Rwolf wrote on 2023-06-02, 19:00: There are some switches you must set on both the PC & XT system board when using the EGA on the older systems. Page 79 in the link below. https://www.minuszerodegrees.net/oa/OA%20-%20 … s%20Adapter.pdf I do have those set. Without them, nothing happens, no beeps.

Re: Original IBM EGA card repair thread

Posted on 2023-06-02, 18:13

The plot thickens. This card works perfectly fine in my IBM PC/AT. HWINFO16 reports "EGA Color" and 64 KB of RAM. A little test program I'm working on that uses graphics mode 0Dh works fine. When in the 5150, and the jumper settings set according to the IBM EGA manual, I get the one long + two short …

Re: Pulling my hair out with EGA programming.

Posted on 2023-06-02, 05:21

I realized that with the default EGA palette the color value is actually the same value that my egaGetPlanesForColor function returns, i.e. it IS the value that you should write to the plane select register. The IBM engineers were way ahead of me. That only sped it up by 10-20% though. Not sure what …

Re: Pulling my hair out with EGA programming.

Posted on 2023-06-01, 04:40

Thank you all for your help so far. Very helpful. Do you guys think I can improve these functions? This feels very brute force-y, like there must be some optimization I can do. The pixel setting is not very fast, although of course I will have to write a blit function for actual graphics drawing. I …

Re: Pulling my hair out with EGA programming.

Posted on 2023-05-28, 21:30

Thanks, guys. Using a far pointer worked. I can write pixels now. You want to write to address 0xa0000, not 0xa000. In real mode you need to split that into segment 0xa000 and offset 0. In Assembler that is done like pano69 said. I'm not exactly sure what's going on in that assembler code. What is …

Pulling my hair out with EGA programming.

Posted on 2023-05-28, 06:03

I can set the video mode. I can set the border color using the EGA registers. Writing 1 to plane 0 on the first pixel to turn it blue, however, seems to be impossible for me, despite it being unfathomably straightforward. outp(0x3C4, 0x02); // select plane-select register outp(0x3C5, 0x01); // plane …

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