Strange thing about the new iMac

Catfish_Man

macrumors 68030
Original poster
Sep 13, 2001
2,579
1
Portland, OR
I was looking at the doc posted a bit ago about how to take it apart and I noticed something strange.

Note: There are two RAM expansion slots. This describes installing a memory module in the internal memory slot located on the main logic board. It uses PC133 168-pin DIMMs up to 512 MB in capacity, requires removal of the main logic board and can only be installed or replaced by an Apple Authorized Service Provider.

The user-accesible slot requiring PC100 144-pin SO-DIMMs (Small-Outline Dual Inline Memory Module) can be upgraded to 256 MB in capacity.

(from page 98)
It uses both PC133 and PC100 RAM. I thought that you needed a 133MHz system bus to use PC133 RAM effectively, and I thought that if you mixed PC100 and PC133 it would run the whole thing at the speed of the slower memory. Am I wrong, or is this strange?
 

U

Unregistered

Guest
Re: Strange thing about the new iMac

Originally posted by Catfish_Man
I was looking at the doc posted a bit ago about how to take it apart and I noticed something strange.



It uses both PC133 and PC100 RAM. I thought that you needed a 133MHz system bus to use PC133 RAM effectively, and I thought that if you mixed PC100 and PC133 it would run the whole thing at the speed of the slower memory. Am I wrong, or is this strange?
It's an odd configuration in general, but I could see it as a way to get everything to fit. As for the whole thing running at the speed of the slower memory, it has a 100mhz system bus anyway, so running at the slower speed shouldn't make any difference as far as I know. I have two different speed DIMMs in my 600mhz iMac and I've never had any problems. Many chip suppliers were sending out PC133s, even when you order 100s, claiming that the 133s will work fine in place of the 100s.
 

datalok

macrumors member
Jan 6, 2002
70
0
well here in Aus 133 is cheaper than 100 and the difference is 133 is rated to run at that speed - most 100's can with no prob but since ram probs are a beatch to pin down it is best to use the 133 - imho
 

gotohamish

macrumors 65816
Jul 15, 2001
1,070
0
BKLN
efficient ram

I believe if you have a 100 bus, ram can fall short of it's mark:

IE - PC100 ram can run at about 90, or 95 - thus lowering your bus speed. If you use PC133 and it runs slower, it's still running at more than 100 so you get full 100 bus speeds.

I think...