RAM and HyperTransport questions...


macrumors 604
Original poster
May 30, 2002
Toronto, Ontario, Canada
How's it hangin everyone??

Its been a long time since I've been here, due to a 3 month pleasure cruise on a used G4 733Mhz QuickSilver that went 2 days before smoking itself a big joint to death while I was away. So I'm outta a computer for a while :( !

Here are my questions.......

DDR SDRAM. I'm aware that there is 3 designations 1600, 2100, 2600. All I know is the higher the number the faster the RAM is on both the rise & fall of the CPU clock speed. What are these designations, and how fast does the ram run at respectively, and also, how is it possible for the ram to run at 166Mhz when the system bus speed is only at 133Mhz???? Does the system bus speed remain the same or while the RAM bus to the CPU increases or what??? Also how does DDR SDRAM affect CPU speed?

What is the XServe's system bus speed??

And lastly, during Steve Jobs webcast of the XServe he mentioned it containing a "HyperTransport" connector inside for future expansion needs, but thats all he commented on it, and thus no questions during the webcast about it either. What the hell is HyperTransport, and what does it mean to a non-graphics professional, office working, gamer like myself?????

Thanks for all the help I can get in advance!!


Moderator emeritus
Jun 25, 2002
Gone but not forgotten.
As far as DDR RAM goes. It operates at twice the bus speed traditionally. What you've listed runs at 200 MHz (2 x 100), 266 (2 x 133.33), and 333 (2 x 166.67). There is also 400 MHz DDR but I don't know the designation, only that's its prohibitively expensive.

XServe uses a 133 MHz memory bus.

HyperTransport, I believe, is an inter-device transfer protocol championed by AMD, Apple, IBM, Sun, and others. You may find the information you require at http://www.hypertransport.org/.
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