muon wrote on 2020-10-24, 17:06:
Grzyb wrote on 2020-10-24, 16:01:
EXT C G = EXTernal Character Generator
You can install there a 2764 ROM chip with some font, eg. one with national characters.
What kind of IC I can Use for the 2764 ROM? I have a Minipro programmer. Where can I get a set of font for the ROM?
You use a 2764 or a 27c64. An 2864 or 28c64 should be compatible. Check you MiniPro documentation for chips with numbers like that. "27" means you need a UV lamp to erase the chip, and the cheapest 27-type chips don't have the window, so you can't erase them at all. "28" means you can electrically erase them within seconds, you just need the minipro to reprogram the device. Any 27-type chip you buy from factory is already erased, so for a single programming process you don't need any erasure.
I don't know what layout the font has to have. If the external font is applicable for the MDA mode, you need 256 characters of 16 bytes each (14 bytes make up the image, and two bytes are wasted, to make the size per character a power of two). This will only use 4K of the 8K of the ROM, so it is likely that they might use the same ROM memory layout as the original MDA and CGA cards (but they use a different pinout!). The original MDA/CGA ROM has two CGA character sets of 2K each (8x8 pixels, one with thick and one with thin vertical lines) and one MDA character set (8x14 pixels). which nicely fits in the 8K you can store in a 2764-type programmable memory.
I don't know good sources for ROM contents, but this thread on Vogons discusses greek CGA/MDA font ROMs.
muon wrote on 2020-10-24, 17:06:
Horun wrote on 2020-10-24, 15:23:
The sockets are for a BIOS chip and Octal latch. Those would add CGA capability if not included in the motherboard iirc.
The jumpers are for setting the video Mono/CGA, LPT port (LPT1, 2, 3 or 4) and video emulation for MDA, Mono CGA, Color CGA.
I have a similar card Everex Edge II but luckily has the jumpers silkscreened....
Where I can get that IC ( Octal latch)?
Anywhere you can buy electronic components. The useful options depend on your location. The chip you need is named "74LS374". The card already says "LS374" on the silkscreen, and the 74 was supposed to be obvious to anyone into digital electronics. There are more modern variants of this chip that should be 100% compatible, like the "74HCT374". The "T" is important for full compatibility, but most likely, any "74...374" chip you can obtain will do.
I suppose the CG jumper is not about "CGA" though, as other posters guessed, but is used to switch between the internal character set and the external character generator ROM.