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AX = 4404h BL = drive number of DoubleDisk drive (00h = default, 01h = A:, etc.) CX = number of bytes (000Ah-0014h, call ignored otherwise) DS:DX -> data record (see #01530)
Return:
CF clear if successful AX = number of bytes read CF set on error AX = error code (01h,05h,06h,0Dh) (see #01680 at AH=59h/BX=0000h)
Program: DUBLDISK.SYS is the device driver portion of DoubleDisk, a disk expander by Vertisoft Systems, Inc.
InstallCheck:
For v2.6, scan memory for the signature "FAT 2.6 byte:", which is immediately followed by a data table (see #01531)
BUG: VOPT (a disk optimizer by Golden Bow Software) assumes that any driver which returns the "correct" number of bytes when the first word of the buffer for the data record contains the signature value 4444h is DoubleDisk; a workaround is for the non-DoubleDisk driver to return no data if the signature is present
See Also: AX=440Dh"DOS 3.2+"
Index:
Installation check;DUBLDISK.SYSFormat of DUBLDISK data record: Offset Size Description (Table 01530) 00h WORD (call) signature 4444h 02h BYTE (call) function 00h ??? 01h ??? ---function 00h--- 02h BYTE (ret) ??? 03h BYTE (ret) ??? ---function 01h--- 02h WORD (ret) 4444h 04h WORD allocation unit size??? 06h WORD ??? 08h WORD ??? 0Ah BYTE ???
Format of DUBLDISK signature data table: Offset Size Description (Table 01531) 00h 5 BYTEs ??? 05h BYTE first drive number 06h BYTE number of drives 07h ???
Category: File/Disk Compression - Int 21h - D
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