On Fri, Jan 28, 2005 at 01:46:22AM -0800, Declan Moriarty wrote:

> P1-233Mhz (I presume a 66 Mhz bus)    142 MB/S Intel 430 chipset
> K6/2-350Mhz   100 Mhz bus(pc100 ram)  127 MB/S SiS chipset
> k6/3-500Mhz   100 Mhz bus (pc100 ram) 130 MB/s Via Chipset
> P3 Coppermine -730Mhz 100 Mhz bus?    242 MB/S Intel 810 chipset
>       (It's loaded with pc100 ram)
> AthlonXP-2.6Ghz       333 Mhz bus (?ddr RAM)  730 MB/S Via Chipset
> 
> Unless the Intel chipsets are feeding the ram twice as fast, I fail to 
> see how these make sense. Particularly, how come Intel seems to get 242 
> MB/S when Via and SiS only get 130 MB/s? How come the humble p233 
> outsprints a k6-500? Which is real?
> 
> I am vague about the Intel stuff because the p3 was _given_ to me, and 
> the p233 is an ex-ebay Industrial cpu card.
> 
> I gather there is some difference in the way clock speeds are measured 
> between AMD and intel cpus. The Athlon was reported as 2.075 Mhz, 
> whereas in fact it's a 2.6Ghz. I have seen BIOS detect it as both. 
> (There was a BIOS revision on the Chaintech MB I have the Athlon in to 
> correct the detected cpu speed).
> 
> Any ideas?

How many RAM-slots are attached? Probably the P3 is using two RAM banks
in parallel but all other just access only to one bank at a time.
(or is DDRRAM attached? double datarate: it reads at both edges of the clock).
The Athlon2.6G is also using ddr ram with a 3 times higher clock, 
your list absolutely makes sense:
all older 100MHz RAMs have 130-140MB/s (single data rate)
the P3 has 2*120MB/s (double data rate)
the Athlohn has 2*3*120MB/s (double data rate, 3 times higher clock)

It is nice to see, that CPU speed has nothing to do with RAM speed.
(at least at higher clocks). However DRAM is getting complicated these days. 
I am not at the state of art level in this topic. But I would expect
1-2 GBytes/s RAM transferrate at high end PC's today.

M.
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Author: Matthias Weingart
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