MHz describes the speed of the computer's microprocessor or CPU (central
processing unit) in megahertz or millions of cycles per second. The speed
of the CPU multiplied by the number of bits or bytes (there are eight bits
in a byte) the CPU processes in each cycle gives one a very rough sense of
how much information the CPU can process in terms of bits per second. For
example, an Intel 486 or a Motorola 68040 processes information in 16 bit
chunks (I think), so a 25 MHz 486 or 68040 could process 25 million x 16
bits each second, or 400 million bits per second, or (rewritten) 400,000
kilobits per second (Kbps). This calculation make the erroneous assumption
that a CPU only takes one cycle to move a chunk of data. However, even if
one changes the assumption such that the CPU requires 100 cycles to move
one chunk, the estimated CPU throughput becomes 4,000 Kbps.
Note that 4,000 Kbps is still ever two orders of magnitude (over 100x) the
throughput of a 28.8 Kbps modem. Another limitation is the throughput of
the serial card or port on your computer, but these remain in the 56 Kbps
and up range, so the bottleneck remains the modem.
I just gave my parents a Mac LC III ($300 for a 25 MHz 68030 processor, not
including monitor) and a Supra 144LC modem, which I expect will be just
fine for beginning www and word processing.
Hope this helps!
JP
------------------------------------------------------------------------------
JOHN W. PILGRIM
Technology & SB1274 Resource Teacher email: pilgrim@muse.sfusd.k12.ca.us
Horace Mann Academic Middle School AOL: Bharati (Pls no mail here)
San Francisco Unified School District vox: 415-695-5881
3351 Twenty Third Street fax: 415-695-5884
San Francisco, California 94110, USA
If you're on the SFUSD WAN, check out http://156.1.28.5/webschool/default.html
-------------------------------------------------------------------------------