Mail Archives: djgpp/1998/02/04/10:15:48
> sorry about the ignorance, but what is dubble buffering?
*Double* buffering is a concept related to the use of memory caches
for reading and writing data to disks (your hard disk). I hope you
know what purpose caches serve. Think of caches as a time-saving
strategy for accessing both code and data quickly from memory rather
than trying to access the disk, which is probably 5-10 (?) times
slower if you do the latter. If what you want is in your cache
(in memory?), you save time; if not, you have to go to disk to get
the parts that you need to use for the moment. This whole notion of
time-saving by using caches is I think what prompted Intel to put 14
levels of caches (yes, I am being facetious) in their CPUs so that
your code and data could be fetched even faster, if you can believe
it, than the time it takes to go from RAM to the CPU.
Rather than try to botch any further an explanation of what a cache
is or is not or why it would be necessary, you can get a MS-DOS
prompt and type in 'help smartdrv' and find the parts related to use
of double buffering. It doesn't really explain the purpose of double
buffering, only if you should use it; why you are not told 'why' but
just 'how' may be a Microsoft customer service policy.
I will help a little by directly excerpting certain parts of the help
screens related to the use of Microsoft's SMARTDRV.
----------<begin excerpt>-------------------------------------------
SMARTDRV.EXE--Notes
Double buffering and conventional memory
SMARTDrive's double-buffering component must be loaded in conventional
memory. It uses 2K of conventional memory, and cannot be loaded in
upper memory.
The SMARTDrive disk cache can use either upper memory or conventional
memory. For more information, see <SMARTDRV--Notes>.
Determining whether you need to use double buffering
If you use EMM386 or run Windows in 386 enhanced mode, you may need to
use double buffering. Double buffering is most commonly required with
an SCSI (small computer system interface) hard disk or other device,
but can also be necessary with an ESDI (enhanced system device
interface) or MCA (microchannel architecture) device.
Most hard disks do not need to use double buffering. If you are not
sure whether your hard disk needs double buffering, follow these
steps:
1 Add the following command to your CONFIG.SYS file if the file does
not already contain such a command:
device=c:\dos\smartdrv.exe /double_buffer
This command must appear before the DEVICE command that starts
EMM386, if any.
2 Add the following command to your AUTOEXEC.BAT file if the file
does not already contain such a command:
c:\dos\smartdrv
3 Run the MemMaker program if you haven't already done so.
4 Use the MEM /C /P command to confirm that upper memory is in use.
5 At the command prompt, type SMARTDRV and then press ENTER.
SMARTDrive displays information about your system.
6 Look at the column labeled "Buffering." If any line in this column
reads "yes," you need to run the double-buffering component of
SMARTDrive. (If your system seems to be running slowly, try adding
the /L switch to the SMARTDRV command in AUTOEXEC.BAT.)
If every line in the "Buffering" column says "no," you can remove
the DEVICE command for SMARTDRV.EXE from your CONFIG.SYS file.
If any line in the "Buffering" column contains the character "-",
then SMARTDrive is unable to detect whether double buffering is
needed. Use the MEM /C /P command to confirm that programs are
located in upper memory.
----------<end excerpt>----------------------------------------------
Let this be the final word, since it was Microsoft that spoke them.
:)
Mitch Halloran
Research (Bio)chemist
Duzen Laboratories Group
Ankara TURKEY
mitch AT duzen DOT com DOT tr
other job title: Sequoia's (dob 12-20-95) daddy
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