Date:	Mon, 10 Apr 95 12:12 MDT
From:	mat AT ardi DOT com (Mat Hostetter)
To:	djgpp AT sun DOT soe DOT clarkson DOT edu
Subject:	RE: timers and smartdrive.exe
References:	<9504051112 DOT AA08398 AT sun DOT soe DOT clarkson DOT edu DOT soe> <Pine DOT 3 DOT 89 DOT 9504101353 DOT A8450-0100000 AT ra DOT isisnet DOT com>

bdavidson AT ra DOT isisnet DOT com writes:
>This rang a bell, so I went to my bookcase and dug out Dr. Dobb's 
>Journal, #184 (Jan. 1992), and there was an article called "Untangling 
>SMARTDrive" by Geoff Chappell (pp 64-72).

Ralf Brown's enormous interrupt list describes this interface.  Here
is the appropriate excerpt.

-Mat



INT 21 - SMARTDRV.SYS - IOCTL - CACHE CONTROL
	AX = 4403h
	BX = handle for device "SMARTAAR"
	CX = number of bytes to write
	DS:DX -> SMARTDRV control block (see below)
Return: CF clear if successful
	    AX = number of bytes actually written
	       = 0000h if control block too small for given command
	CF set on error
	    AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4402h"SMARTDRV",INT 2F/AX=4A10h/BX=0000h

Format of SMARTDRV control block:
Offset	Size	Description
 00h	BYTE	function code
		00h flush cache
		01h flush and discard cache
		02h disable caching (flushes and discards cache first)
		03h enable caching
		04h control write caching
		05h set flushing tick count
		06h lock cache contents
		07h unlock cache contents
		08h set flush-on-reboot flag
		09h unused
		0Ah control full-track caching
		0Bh reduce cache size
		0Ch increase cache size
		0Dh set INT 13 chain address
---function 04h---
 01h	BYTE	write caching control action
		00h turn off write-through
		01h turn on write-through
		02h turn off write buffering (also flushes cache)
		03h turn on write buffering (also flushes cache)
---function 05h---
 01h	WORD	number of timer ticks between cache flushes
---function 08h---
 01h	BYTE	new flush-on-reboot flag (00h off, 01h on)
---function 0Ah---
 01h	BYTE	full-track writes are
		00h not cached
		01h cached
---functions 0Bh,0Ch---
 01h	WORD	number of 16K pages by which to increase/reduce cache size
---function 0Dh---
 01h	DWORD	new address to which to chain on INT 13
Note:	the previous address is not preserved

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