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Format of DOS 4.01 (from UR 25066 Corrctive Services Disk on) disk buffer info

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Offset Size Description

00h

DWORD

pointer to array of disk buffer hash chain heads (see #01654)

04h

WORD

number of disk buffer hash chains (referred to as NDBCH below)

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

01h, possibly to distinguish from pre-UR 25066 format

0Dh

WORD

??? EMS segment for BUFFERS (only with /XD)

0Fh

WORD

??? EMS physical page number of EMS seg above (only with /XD)

11h

WORD

??? EMS segment for ??? (only with /XD)

13h

WORD

??? EMS physical page number of above (only with /XD)

15h

BYTE

??? number of EMS page frames present (only with /XD)

16h

WORD

segment of one-sector workspace buffer allocated in main memory if BUFFERS/XS or /XD options in effect, possibly to avoid DMA into EMS

18h

WORD

EMS handle for buffers, zero if not in EMS

1Ah

WORD

EMS physical page number used for buffers (usually 255)

1Ch

WORD

??? appears always to be 0001h

1Eh

WORD

segment of EMS physical page frame

20h

WORD

??? appears always to be zero

22h

BYTE

00h if /XS
01h if /XD
FFh if if BUFFERS not in EMS

See Also:

#01649,#01650,#01652,#01657