I worked with a programmer who cut his teeth on ancient iron in the 1950s. He had a computer that had 4K of ram and two 512 byte I&#x2F;O buffers. He would set the loader for the program into the I&#x2F;O buffer and then use that to load and initialize the rest of the program. The I&#x2F;O buffers would go away on the first read&#x2F;write. Every byte counted.
I used the same techniques when I wrote MASM in the 1990s to create a 16k I&#x2F;O buffer in the CGA graphics card. The graphics card memory was slower than regular memory, but the 16K made the program fly on reads and writes.
I remember a utility that used the Hercules Video card memory for EMS (paged) memory. I think it came with the card.