Using a Compressed RAM Disk
Although the technique described here is interesting, its usefulness is
debatable. Some experts say that you can get better mileage out of your
extended memory by using it in a disk cache. However, a large RAM disk
used as your TEMP directory will speed up I/O Redirection and Windows
Print Manager tremendously.
A compressed RAM disk provides nearly double the storage for the same
amount of RAM. The speed difference is negligible (it's still far faster
than the fastest uncached hard disk).
■ You must install the RAM disk earlier than DBLSPACE.SYS in your
CONFIG.SYS file. Otherwise, each time you mount the RAM disk,
DoubleSpace will modify DBLSPACE.INI to take over its drive ID (and the
next time you boot, the RAM disk's ID will be one notch higher... ad
■ You must have at least one available DoubleSpace reserved drive ID.
Use Dblspace /LIST to check this. If not, run Dblspace, choose Options
from the Tools menu, and change the setting.
█▌The Simple, Vanilla Technique▐█
■ Create a 1.2 MB RAM disk. For instance..
DEVICEHIGH=c:\dos\ramdrive.sys 1200 /E (in CONFIG.SYS)
DEVICEHIGH=c:\dos\Dblspace.sys (in this order)
...and create a compressed drive....
DBLSPACE /CREATE D: /NEW=E: /SIZE=0.50 (in AUTOEXEC.BAT)
DBLSPACE /SIZE /RESERVE=0 E: (no reserved space needed)
...each time you boot.
■ This slows-down your boot sequence and you may want to use less than
1.2 MB for your RAM disk.
█▌The Interesting Technique▐█
Create a "dummy" compressed volume file on a diskette. Copy it to your
hard disk. In AUTOEXEC.BAT, copy it to a RAM disk and mount it. A
600K RAM disk will yield about 1 MB of fast RAM disk storage.
1) Format a 1.2M diskette in drive A...
Format a: /U /VDbl_RAMDisk
2) Create a minimum-size CVF▲ on the diskette; for instance,
Dblspace /COMPRESS A: /res=0
Dblspace /SIZE=0.56 A:
3) Unmount the compressed volume:
Dblspace /UNMOUNT A:
4) Clear the attributes of the CVF:
Attrib -h -r -s A:\DBLSPACE.000
5) Copy the CVF to your hard disk, giving it a different name:
Copy A:\DBLSPACE.000 C:\DUMMY.CVF
Note: You no longer need the compressed diskette.
6) Setup CONFIG.SYS to create a 600K RAM disk; for instance:
DEVICEHIGH=c:\dos\ramdrive.sys 600 /E
Put this BEFORE installing DBLSPACE.SYS. We'll assume that your RAM
disk is drive D.
7) Setup AUTOEXEC.BAT. Add these lines:
SET RAMDRV=D: (create a handy e-var)
Copy C:\DUMMY.CVF %RAMDRV%\DBLSPACE.000 (put CVF on RAM disk)
Dblspace /MOUNT %RAMDRV% (make it accessible)
Reboot. From now on, drive D (or whatever) will be your compressed RAM
drive and its host will have a higher letter, such as E or F.
■ Between steps 2 and 3, pre-load the diskette with often-used programs
and batch files. When you mount the pre-filled CVF, the programs will
be ready for action.
While you're at it, create a TEMP directory on the diskette. And in
AUTOEXEC.BAT, use Set TEMP=%RAMDRV%\TEMP.
■ Steps 2 and 6 minimize the memory use of the RAM disk. The technique
works fine for larger RAM disks (in fact, you may want to use about 1MB
to get best performance from Windows Print Manager).
■ In step 5, be sure to store the dummy CVF on a compressed disk; since
it is mostly empty (and it was formatted with /U in step 1), it will
take very little physical disk storage.
■ General tip for using RAM disks: Step 7 creates an e-var to identify
the RAM disk. In batch files that refer to the RAM disk drive ID, use
%RAMDRV%\ in place of D:\. That way, if you end up changing the drive
ID of the RAM disk, one change to AUTOEXEC.BAT fixes all of your batch
files and MAKE files.
Notes: ■ In nearly all respects, DoubleSpace treats a RAM disk as if it
were a hard disk. The one apparent difference is in
Dblspace /LIST, it will identify a disk as a "Compressed
RAMDrive" or "Local RAMDrive" only if its volume label is
■ By default, Smartdrv will provide disk caching for a compressed
RAM disk. This is particularly wasteful (if somewhat
humorous). Be sure to disable all caching for your RAM disk;
for instance, if the RAM disk host drive is E, add E- to the
Smartdrv command line in your AUTOEXEC.BAT file.
See Also: DoubleSpace (overview)