Format of DOS 5.0-6.0 disk buffer info:
Offset	Size	Description	)
 00h	DWORD	pointer to least-recently-used buffer header (may be in HMA)
		(see #01655)
 04h	WORD	number of dirty disk buffers
 06h	DWORD	pointer to lookahead buffer, zero if not present
 0Ah	WORD	number of lookahead sectors, else zero (the y in BUFFERS=x,y)
 0Ch	BYTE	buffer location
		00h base memory, no workspace buffer
		01h HMA, workspace buffer in base memory
 0Dh	DWORD	pointer to one-segment workspace buffer in base memory
 11h  3 BYTEs	unused
 14h	WORD	???
 16h	BYTE	flag: INT 24 fail while making an I/O status call
 17h	BYTE	temp storage for user memory allocation strategy during EXEC
 18h	BYTE	counter: number of INT 21 calls for which A20 is off
 19h	BYTE	bit flags
		bit 0: ???
		bit 1: SWITCHES=/W specified in CONFIG.SYS (don't load
			WINA20.SYS when MS Windows 3.0 starts)
		bit 2: in EXEC state (INT 21/AX=4B05h)
 1Ah	WORD	offset of unpack code start (used only during INT 21/AX=4B05h)
 1Ch	BYTE	bit 0 set iff UMB MCB chain linked to normal MCB chain
 1Dh	WORD	minimum paragraphs of memory required by program being EXECed
 1Fh	WORD	segment of first MCB in upper memory blocks or FFFFh if DOS
		  memory chain in base 640K only (first UMB MCB usually at
		  9FFFh, locking out video memory with a DOS-owned memory
		the MCB this word points at contains a valid link into high
		  memory even if it is marked with a 'Z' indicating the last
		  memory block
 21h	WORD	paragraph from which to start scanning during memory allocation
SeeAlso: #01652,#01653