From the initial article I expected some Bus mastering DMA, or at least ISA DMA, but its a big shared memory window. For ISA Network card choices were: Bus Mas

From the initial article I expected some Bus mastering DMA, or at least ISA DMA, but its a big shared memory window. For ISA Network card choices were: Bus Mastering - fancy and fast, but troublesome with lots of ram and/or in protected mode http://www.os2museum.com/wp/vds-borne-out-of-necessity/ http://www.os2museum.com/wp/vds-borne-out-of-necessity/ ISA DMA - slow, example AMD Lance Am7990 like Novell NE2100. Maximum original 8237 DMA controller throughput was ~1MB/s while stealing 100% of ISA bus thus stalling CPU completely. Memory sharing - also problematic because you lose precious DOS memory. Port IO - like good old NE2000. Small software interface footprint, fast with 286/V20 'REP INSW/OUTSW'.