CGA clones, Plantronics, more than 640 RAM on IBM 5150

[gordonf4vcf]

Hello, first time here. I haven't dealt with XTs for decades but here's an IBM 5150 that dropped into my lap.

Never mind that it didn't quite work in this video. I've since managed to get the MDA monitor working, and the PC boots to a FA00 ROM error, meaning one of the four ROMs for Cassette BASIC is messed up. I already have plans to address this in the coming days.

What I'd like to attempt, is get a CGA compatible adapter card, the GlaBIOS firmware, and a 1 MB RAM card to wring out more than 640 KB RAM usable by DOS. There are plenty of reproduction CGA cards out there including the breakout project card from the Book8088 PC. I already have 2364 to 27xxx adapters from my Commodore projects, so I could put this in and remove the corrupted Cassette BASIC ROMs. I could also stick with the MDA card that's in there now and still get a little more than 640 KB.

But to go an extra mile I'd like to try one of the Plantronics clones out there. It looks like these have BIOSes of their own however, such as the ATI Graphics Solution card, which I'm worried would prevent using more than 640 KB RAM. The original Plantronics didn't appear to have a BIOS ROM.

Is there a "Super CGA" card that would still work with GlaBIOS to wring out more than 640 KB RAM?

It's also possible I'm hosed anyway, due to also wanting an XT-IDE card with its own BIOS in there. In fact the 1 MB card was one I ordered from Monotech as part of the XT-IDE combo to save on card slots.

If it ends up not being possible to wring more RAM out of this system, I'll just skip this nonsense and get one of the VGA cards that work in 5150s.
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[JohnElliott]

I don't think the ATI Graphics Solution had a BIOS ROM, only a character ROM. In general CGA / Plantronics cards didn't have BIOS extensions, but EGA cards that could emulate Plantronics (like the Paradise EGA) did.

 

[Plasma]

By "more than 640K", I assume you mean contiguous and not UMBs. In that case, you want a graphics card that doesn't have memory at A000 (i.e. no EGA/VGA). Video BIOS doesn't matter since it will be somewhere in C000.

For the maximum amount of conventional memory (736K), you also want no MDA/Hercules, so you can use all the memory up to B800. Monochrome cards start at B000, which would limit you to 704K.

It looks like ATI Graphics Solution would allow 736K in color mode or 704K in monochrome mode.

 

[gordonf4vcf]

Nice. I forgot about character ROMs. I’ll try to find one of the ATI cards then.