----------------------------Original message----------------------------
> I just had to comment.  If you want speed, you need to consider the speed of
> the bus.  The processor may run at 66 mmhz, but your bus (motherboard) is
> pushing the data around at a maudlin' 10 mhz depending on the motherboard's
> architecture (ISA, EISA, microchannel).
 
Tis true, however you have to consider where the data is coming
from.  Memory is typically NOT on the main bus so isn't affected.
Then you must consider how fast the data source can supply the
data, will it saturate the 5meg/sec speed of the ISA bus?
 
A modem? never.  Ethernet? probably not.  Hard drive? maybe.
Video? yes!.
 
> This why local bus options are
> so popular.  IMHO, a local bus option for the disk drive is important if
> you are doing a lot of disk read/writes, this is true if you are using the
> the disk caching.
 
In many situations, the limits of the hard drive come into play
before the limits of the bus and there are other important
factors as well.
 
For example, I have 2 hard drives with similar published
performance specs, one SCSI and one IDE.  I get over twice the
throughput on the SCSI disk connected through an ISA bus than
from the IDE disk on a local-bus.  Furthermore, the SCSI
controller does DMA so the CPU load is tiny compared to the IDE.
This may not be important under DOS, but it makes a big
difference in a multitasking system such as Unix (which I use),
OS/2 or NT.
 
Having said that, if you have multiple hard drives feeding
through an ISA bus *and* a multitaksing OS to keep them all
reading/writing at full tilt, the bus speed does come back into
the picture.
 
-john
 
== John Fieber ================================== Young Science Library ==
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