Originally posted by ddtlm
Telomar:
What? Your entire position is rediculous. Bandwidth is a measurement of flow of data. Data is beasured in bytes, kilobytes, megabytes and gigabytes, etc etc. These each are different from each other by exactly a factor of 1024, not 1000. 1000 is wrong, and always will be. There can be no discussion of that claim because it is absolutilty totally wrong.
The P4 and PPC-970 have the number I have presented. Marketeers prent inflated, wrong numbers because they can get away with it. But they are still wrong. The P4 bus cannot transfer the data that is claimed, nor can the PPC-970 bus, and therefore the figures you quote are wrong.. Ok? They are wrong. End of discussion.
Totally wrong. Only marketeers use factors of 1000 because it distorts the truth in their favor, in all other cases all matters of memory are referred to in powers of 2, and factors of 1024 (2^10).
Because of overhead only 800mhz of this is available for transferring data. The P4 bus, and no other common bus, suffers from this design drawback. IMHO, IBM is stretching the truth to claim it is 900mhz because it does not transfer useful data at that rate under any circumstances.
You really don't have the first clue what you are talking about. Next you will try and teach people a kilowatt is really 1024 watts and not 1000 and the power companies are just out to extort money from you
The following prefixes are all predefined SI prefixes:
Kilo, Mega, Giga, Tera, Peta, etc.
Any engineer, scientist or person who has passed high school is aware that they are defined as official prefixes meaning 10^3, 10^6, 10^9, 10^12 and 10^15. You can check that with any national standards body.
Computer OSs and memory rely on a binary system however and it was easier in the early days to just take the nearest SI prefix (especially since they didn't have prefixes of their own). The answers aren't actually correct though and 1024 bytes isn't actually a kilobyte, that's 1000 bytes. By convention it was accepted due to the lack of other prefixes but it isn't correct nor has it ever been. The error has simply been ignored.
As time went on the error associated with this method of binary calculation and using SI prefixes becomes a larger and larger problem to the extent that in 1998 a new set of prefixes were defined for binary numbers to deal with it. You take the first two letters of the old prefix and add bi. ie:
Kibi, Mebi, Gibi, Tebi, etc = 2^10, 2^20, 2^30, 2^40 and so forth.
Now computer operating systems and memory manufacturers had good reason to use binary numbers and since they didn't have their own prefixes could previously be excused but bandwidth and storage never had such a reason so have used the prefixes as properly defined.
As for bus overhead every bus has overhead. The MPX bus, which is among the most efficient around runs at roughly 15% overhead. And it only even achieves those numbers in very specialised cases. Generally the number is closer to 25%. PC buses are generally worse still operating at around 65% of theoretical numbers or so. No small part of this is just inherent in operational costs of a bi-directional bus.
No other bus suffers that same area of overhead but every bus suffers from overhead. Also uni-directional buses allow for some reduction in overhead associated with a bi-directional bus.
I'd be expecting much better throughputs out of IBM's pair of uni-directional buses than from a PIV bus (except in the case where data streams in almost solely one direction). All buses have overheads so if you plan to factor in the PPC970's then factor in the PIV's.
