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一款DOS下的RAM disk和disk cache组合在一起的工具。

                        COMBI-Disk -
                   RAM disk & disk cache


Preface.
--------

        - Why don't You use disk cache?
        - I'd like, but memory constrains prevent me from using it:
          I need more memory for  RAM disk.
-----
        - Why don't You use RAM disk?
        - I'd like, but memory constrains prevent me from using it:
          I need more memory for disk cache.
-----
        - Why don't You use RAM disk or disk cache?
        - I'd like, but some of my applications require free extended
          memory.

If one of these answers is Yours then COMBI-Disk is for You!
You may hit THREE targets with a single shot - installing COMBI-Disk
You get a RAM disk and a Disk-Cache and free XMS memory at the same
time in the SAME area of extended memory!

When You install COMBI-Disk You specify amount of extended memory for
it and You get a RAM disk of the specified size and a Disk-Cache of the
same size. You may also specify amount of memory which should be
released if some program requires it. Then when You work with Your PC,
You enjoy COMBI's disk cache which is not worse than others (I hope it
is better).  Suppose now that You start a program which needs a disk
buffer for temporary storage and tell it to use RAM disk.  Then the
program may use the whole amount of the RAM disk's space (though
contracting the size of cache).  When it terminates and deletes
temporary files You get back your cache buffer!  If a program requests
XMS memory COMBI-disk may loan some of its memory to the program (if it
has the requested amount free of RAM disk data). When the program
releases the memory COMBI-disk reallocates it back.


Applications.
------------

Some programs (e.g. compilers, word-processors etc.) need a buffer for
temporary storage, and if the storage is RAM disk then their performance
may be increased few times compared with the case of usage of hard disk
instead. That's why You may sometimes need a RAM disk. But if You use
standard RAM disk (Microsoft (C) RAMDRIVE.SYS or IBM (C) VDISK.SYS or any
other) it often comes out that it stays empty most of the time though
consuming Your extended (expanded) memory. That's why You may wish to
give up using RAM disk or make it less in order to have more memory
for disk cache which is always useful.

Moreover, some of programs can take advantage of XMS memory if it is
available. That's why You may wish to give up using disk cache (though
some of caches support memory reallocation without reinstallation).

                Don't get disappointed!
     COMBI-Disk
is a nice solution of this problem! It uses a little more memory for
RAM disk than is needed to keep all files written into it while all the
remaining memory is used for cache.  You need not bother to make this
memory larger - just WRITE Your file(s) into RAM disk, all the rest it
does itself! You need not bother as well to contract RAM disk's size
and increase cache size - just DELETE files from RAM disk and all the
released memory will be used for cache!  You need not bother to
reconfigure Your system when You need some free XMS memory - COMBI-disk
takes care of that itself (however, if You forgot to specify amount of
memory COMBI-disk would release, You have to run COMBI control program
to tell COMBI-disk that You need certain amount of free XMS memory).


System requirements.
-------------------

        1. 80x86 based machine with extended memory.
        2. DOS 3.30+.
        3. Extended memory manager which supports XMS 2.0 specifications
	   which supports "reallocate XMS" function (Microsoft (C) HIMEM.SYS
           ver 2.77+ or Quarterdeck (C) QEMM.SYS will do, as well as most
           others).


General features.
----------------

        - COMBI-disk may use up to 16 Mbytes of extended (XMS) memory.
        - Up to 8 physical hard disks are supported.
        - Starting from version 1.00 background write caching is
          supported.
        - Automatic reallocation of XMS memory.
        - Variable size of cache block (memory allocation unit) -
          from 1 to 8 disk sectors (512 bytes each).
        - IOCtl interface to control program.
        - HMA may be used for COMBI-disk data tables (even when MS-DOS
          5.0 is loaded into HMA and under DR-DOS 6.0 as well).


Installation.
------------

Warning! It is recommended to make backup of hard disk before
installation of COMBI-disk (as well as any other disk cache program).

COMBI-Disk installation process is quite straightforward, although it
requires some tweaking with the contents of your CONFIG.SYS file. Copy
COMBI.SYS into Your hard-disk and insert the following line into Your
CONFIG.SYS file

        DEVICE=[drive:][path]COMBI.SYS [<parameters>]

The proper place in CONFIG.SYS would be after all memory managers,
after disk managers and if possible before disk write-protection
programs (otherwise You should not turn on write caching).

The <parameters> are all optional and include:

[<buff_size> [<rls_size>]] [/V [<RAMd_parms>]] [/C [<cache_parms]] [/H] [/Q]



<buff_size> -  the amount of XMS memory (Kbytes) You want to use for
               COMBI-Disk. Minimum  is 128K, maximum is about 14000K.
               If it is omitted then all available memory is default.
               There is no harm if You specify more memory than really is
               available - then COMBI-disk uses all available memory.

<rls_size>  -  maximum number of XMS memory (Kbytes) COMBI-disk should
               release when it is requested. Default is 0. Note, if You
               want to specify this number You should also specify
               <buff_size>.

/V          -  means that RAM disk parameters follow.

<RAMd_parms> - RAM disk parameters may be the following:

F:<disk_size>- specifies formatted size of RAM disk. By default COMBI
               creates RAM disk of the size (<buff_size> - <rls_size> -
               - <min_cache>) Kbytes, so that there would never arise
               problem that there is not enough free XMS memory to
               allocate for RAM disk. But You may (and I recommend You)
               specify larger size: up to (<buff_size> - <min_cache>) -
	       that gives You maximum flexibility though sometimes may
	       cause errors if the same program that borrowed XMS from
	       COMBI tries to write a lot to RAM disk.

R:<root_num> - number of entries in root directory of RAM disk. Default
               is 64. If You encounter DOS error "can't create file..."
               when number of file in root directory is 63 (plus one
               for volume label) then try specifying, say, R:128.

S:<sect_size>- sector size for RAM disk - 256 or 512 bytes, default is
               512 bytes. Using 256 bytes sectors may sometimes save
               some space on RAM disk but this is effective only if
               RAM disk size is less than 1 Mbyte.

N           -  tells RAM disk not to return 'sector not found' error
               (see also below). This setting may be always changed by
               control program.

/C          -  means that cache parameters follow.

<cache_parms>- cache parameters may be the following:

M:<min_cache>- specifies minimum cache size (Kbytes). This reduces size
               of RAM disk but guarantees that specified amount of
               memory will be always allocated to cache. Default is 0.

U:<block_sec>- number of sectors per cache block (from 1 to 8). Using
               smaller blocks may result in more effective usage of
               memory (if You have not much of it) but leads to slower
               operation for large read/write transfers. Default is 8.

O           -  tells COMBI-disk to turn OFF disk cache after
               installation. Cache may be turned ON at any time by
               control program. This may be useful for testing period
	       if You have some problems.

B           -  enable background disk writes. By default background
               writes are set off on installation. May be changed at
               any time by control program.

I           -  forces COMBI's disk cache to start background writing
               immediately. By default background writing starts within
               18 timer ticks (approx. 1 sec.) after last access to hard
               disk. This is in effect only when background writing is
               enabled. I admit that sometimes it may be more safe to
	       start writing immediately rather than wait a second, but
	       as a rule that slows down cache performance, especially
	       for large transfers.

/H          -  tells COMBI-disk to use HMA for data tables.

/Q          -  tells COMBI-disk not to display installation parameters.

In short, recommended installation parameters for best performance are:

DEVICE=<drive>:<path>COMBI.SYS 16000 16000 /V F:16000 /C B /H

In this case COMBI allocates all available XMS memory but will release
almost all when it is requested, RAM disk is created of maximum size
and write caching is enabled. (You may use other numbers instead of 16000
if You have less than 16 Mbytes of XMS or don't want to spend all XMS
for COMBI.)

Note:   Minus ('-') may be used everywhere in command line instead of
        slash ('/'), and equal sign ('=') instead of colon (':'). Case
        of the letters is insignificant. Spaces are required only after
        COMBI.SYS name and between two adjacent numbers.


Installation messages.
---------------------

                COMBI-Disk: RAM disk & disk cache
        Copyright (C) 1991, 1992 by Vadim V. Vlasov, Moscow, Russia,
                        Version 1.10

             - This banner always appears and tells You that
               COMBI-disk is being installed.


ERROR: Incorrect DOS version!

             - DOS version must be above or equal to 3.30 and below 6.00.

ERROR: Invalid parameter!

             -  An invalid parameter appears in command line or some
                parameter is specified in improper place.

ERROR: Extended Memory Manager not present!

             -  COMBI-Disk needs XMM driver. Check that Your XMM driver
                is installed before COMBI-Disk.

ERROR: No extended memory available!

             -  All Your extended memory is used by some other programs
                or less than 128K is available.

ERROR: Can't allocate extended memory!

             -  An error encountered when COMBI-Disk tried to allocate
                extended memory.

ERROR: Not enough memory!

             -  Not enough memory for COMBI-disk's code and data. This
                is almost impossible.

ERROR: No hard drives on system(?!)

             -  COMBI-disk can't determine presence of hard disk(s) and
                its (their) parameter(s).

WARNING: Inconsistent parameters.

             -  Some of numeric parameters conflict with each other. As
                a rule this is not fatal - some of the numbers will be
                adjusted.

WARNING: Can't hook XMS driver entry chain.

             -  COMBI-disk won't intercept XMS (re)allocation calls and
                hence automatic reallocation of COMBI's memory is
                disabled. However, You may change amount of used XMS
                memory by control program.

WARNING: Not enough HMA for data tables or HMA not available.

             -  COMBI-disk will use more low memory for its data tables.
                (For 3 Mbytes buffer it is about 10K)

If "ERROR:..." message is displayed COMBI-disk aborts installation.

If the installation is successful a table appears (if it is not
disabled by /Q switch) which summarizes installation options and
announces how much memory is used by COMBI-disk.

Note. Some of numeric parameters specified in command line may be
adjusted by COMBI-disk.


Testing.