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. (VDSsee Virtual DMA Specification) - GET VERSION AX = 8102h DX = 0000h Return: CF clear if successful AH = major version number AL = minor version number BX = product number (see #03217) CX = product revision number always 0000h for QMAPS and HPMM.SYS always 0001h for Microsoft's EMM386.EXE v4.20-4.41 DX = flags (see #03219) SI:DI = maximum DMAsee Direct Memory Access buffer size CF set on error AL = error code (see #03218) Note: bit 5 of 0040h:007Bh is supposed to be set if VDSsee Virtual DMA Specification is supported; this is apparently not always the case SeeAlso: INT 2C/AX=002Bh,INT 31/AX=0400h,MEM 0040h:007Bh"4Bh" Index: installation check;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. (Table 03217) Values for VDSsee Virtual DMA Specification product number: 0000h for Quadtel's QMAPS and Hewlett-Packard's HPMM.SYS 0001h for Microsoft's EMM386.EXE 0003h for Windows 3.x WIN386.EXE 0300h OS/2 (all versions to date) 0EDCh for DR DOS 6.0 EMM386.SYS 4560h ("E`") for Qualitas' 386MAX 4D43h ("MC") for V Communications' Memory Commander 5145h ("QE") for Quarterdeck's QEMM-386 524Dh ("RM") for Helix's Netroom RM386 (Table 03218) Values for VDSsee Virtual DMA Specification error code: 01h region not in contiguous memory 02h region crossed a physical alignment boundary 03h unable to lock pages 04h no buffer available 05h region too large for buffer 06h buffer currently in use 07h invalid memory region 08h region was not locked 09h number of physical pages greater than table length 0Ah invalid buffer ID 0Bh copy out of buffer range 0Ch invalid DMAsee Direct Memory Access channel number 0Dh disable count overflow 0Eh disable count underflow 0Fh function not supported 10h reserved flag bits set in DX Bitfields for VDSsee Virtual DMA Specification flags: Bit(s) Description (Table 03219) 0 PCIBM PC/XTIBM PC XT bus (DMAsee Direct Memory Access in first megabyte only) 1 physical buffer/remap region in first megabyte 2 automatic remap enabled 3 all memory is physically contiguous 4-15 reserved (zero)