INT 4B - Virtual DMA SpecificationA set of interrupt calls which permit the use of DMA even on systems running in protected or Virtual-86 mode with their address remapping, or systems such as Micro Channel PSIBM PS/2, any model/2s with multiple bus masters independently performing DMA operations. - UNLOCK DMAsee Direct Memory Access REGION AX = 8104h DX = flags bit 0: reserved (zero) bit 1: data should be copied out of buffer bits 2-15 reserved (zero) ES:DI -> DMAsee Direct Memory Access descriptor structure (see #03221,#03222) with region size, physical address, and buffer ID fields set Return: CF clear if successful DDS physical address field set DDS buffer ID field set (0000h if no buffer allocated) CF set on error AL = error code (see #03218) DDS region size field filled wth maximum contiguous length in bytes Note: Windows 3.0 does not check whether the region extends beyond the end of a segment BUG: Windows 3.0 in enhanced mode does not return a correct code on error SeeAlso: AX=8103h,AX=8106h