> The video memory is SRAM, not RAM. The SRAM on the MDA card can be used by MIOS as general-purpose memory for creating a Stack Segment (SS) and Extra Segment (ES). Using SRAM avoids the complexity and resource requirements of servicing an interrupt for memory refresh.
That's not just original its wonderfully nuts.
Reminds me of a trick in use around that time, the CGA (and EGA) adapters and the Mono/text adapters used different resource regions and you could have one of each in a system. Then the RAM on one or the other could be used by software, with possibly useful diagnostic display side effects; while the other display was used for the normal display purposes.
That was not a common trick, that guy was also soldering together 1MB RAM pack for Commodore 64's in that time frame too.
All sorts of tricks can be used. I remember using Monochrome RAM B000-BFFF in EMM386.EXE to save upper memory. Don't forget the ROM area that IBM PCJr carts use.
Commodore 64 had a lot of hacks, had a Mimic from Spartan that turned the Commodore 64 into an Apple II clone.
> The video memory is SRAM, not RAM. The SRAM on the MDA card can be used by MIOS as general-purpose memory for creating a Stack Segment (SS) and Extra Segment (ES). Using SRAM avoids the complexity and resource requirements of servicing an interrupt for memory refresh.
That's not just original its wonderfully nuts.
Reminds me of a trick in use around that time, the CGA (and EGA) adapters and the Mono/text adapters used different resource regions and you could have one of each in a system. Then the RAM on one or the other could be used by software, with possibly useful diagnostic display side effects; while the other display was used for the normal display purposes.
That was not a common trick, that guy was also soldering together 1MB RAM pack for Commodore 64's in that time frame too.