Specifications

Computer Architecture and Maintenance (G-Scheme-2014)
Disk caches
A disk cache is a program to speed up disk access by storing the most frequently use
information in the computer's memory and reading ahead from the disk in
anticipation. With floppy disks, the time saved can be spectacular. Writes are almost
always performed to the disk to prevent loss of data in case of power failure. Example:
PC-CACHE, as supplied with PC-Tools. A shareware product is EMMCACHE.
Print spoolers
A print spooler utilises the computer's memory as a high speed buffer so that a fast
computer is not slowed down by a slow printer. For example you can print a 100 page
database report and then load a spread sheet program, print reports and graphs, then
use your wordprocessor while the database report is still printing. Print spoolers that
use extended memory usually come with the memory card. The AST SUPERSPL is a
good example of a spooler with lots of options. A shareware product is EXTSPL.
Q.Difference between Extended and Expanded Memory
Ans. Extended memory
Memory addresses greater than or equal to one megabyte are called extended
memory. The 8088 and 8086 PCs can't have extended memory because these chips can
access only addresses of less than one megabyte (1MB) in size.
With the minor exception of the High Memory Area (HMA), extended memory can be
addressed only by applications run in real mode. It is possible, however, for DOS
applications to make use of this memory to store data (but not to execute code directly
from there). XMS (eXtended Memory Standard, promulgated by Microsoft) permits
applications to allocate extended memory and takes care of copying data to and from
extended memory and conventional memory so that the application does not have to
worry about switching between modes.
Like EMS, XMS usually requires loading a device driver of some sort. Extended
memory is limited to 15Mb on 286es and 386SXes (15Mb extended plus 1Mb
conventional and upper memory equals 16Mb, or 224, 24 being the number of address
lines coming out of the CPU), limited to 4 gigabytes (232) for 386DX chips and up,
although very few motherboards have been designed to hold that much memory.
Expanded memory
Expanded memory is addressed from within the lower 1MB space, usually above 640K.
Prepared By – Prof. Manoj.kavedia (9860174297 – 9324258878 ) (www.kavediasir.yolasite.com)
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