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Old 11-28-2003, 08:10 AM   #1 (permalink)
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Default Newbie DDR question...

After scanning through some posts, I still have a few questions.

I just bought a system with 128MB/PC2700, figuring to upgrade the memory myself. According to the manual, it will support either 2100, 2700, or 3200.

So, if I add another stick of 258MB/PC2100, will the system run better due to additional RAM or slower due to different memory speed? Will it run better but not as fast as if they were both PC2700?

Also, I don't really understand "dual channel" memory or it's advantages. 1) How advantageous is it? 2) Do the memory sticks have to be the same speed? 3) Do the memory sticks have to be the same size (MB)? 4) How do I know if I am running dual channel or not?

I really appreciate any education that you can give me on this topic. I guess everyone has to start somewhere....

Thanks-- BAW

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Old 11-28-2003, 12:03 PM   #2 (permalink)
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It's always better to have memory at the same speed. If you have two different speed modules, the bus will be clocked to the speed of the slowest stick.

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Old 11-28-2003, 01:48 PM   #3 (permalink)
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TigerB, firstly let me welcome you here! Always a boon to have another eager mind to learn and share the knowledge.

Firstly, to answer you quesition, the term PC2100 means that the RAM can run at 266 Mhz, while PC2700s at 333 and PC3200s at 400. There're PC3500s and higher in the market now if I'm not mistaken. Naturally, the higher the hz the faster it'll run. Now to answer your questions:

1. DDR stands for Double Data Rate. With DDR, under optimal conditions twice as much data can be obtained from the memory subsystem during the same amount of time. In most modern PCs, memory data is provided to the processor in "synchronous" fashion. This means that data arrives rhythmically, to the beat of a drum (a tick of a clock, in fact...). The memory clock is actually an electrical signal that bounces between two voltage levels, and shown in the picture to the right.

With standard SDRAM, data is transferred from the memory to the processor when the clock signal bounces from LOW to HIGH. With DDR, data is transferred not only when the clock signal goes from LOW to HIGH, but also when the clock signal goes from HIGH to LOW. Voila! Twice as much data on each tick of the clock!

2. As ZeekDaGeek has said, if you have 2 different RAM at different speeds, it'll use the lower one.

3. No they don't need to be the same size. A combo of 128 and 512 is fine.

4. The make of your motherboard would mention it in the manual or the package it came in. As you've read the manual, it supports up to PC3200.

Hope this helps, :-). Cheers mate!
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Old 11-28-2003, 01:58 PM   #4 (permalink)
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Thanks for the info. Mucho gracias...

I have another question: I have three sticks of DDR memory--

(I know... It's not a lot of memory) I only have two slots on my board. I was trying to decide between
a) 382MB @ 333 or
b) 512MB at the default lowest speed of 266 (and possibly dual channel???)

I finally decided on option A and when I plugged it in and fired it up, my system utility told me that my memory was running at 266MHz. WHAT'S UP WITH THAT?

Thanks again...
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Old 11-28-2003, 02:12 PM   #5 (permalink)
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Sounds as though it might be the BIOS settings? Try going in there and leave the RAM settings at default. This should allow it to detect the RAM settings automatically.
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Old 11-28-2003, 03:31 PM   #6 (permalink)
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TigerB you said you have 3 memory modules installed? if one of them was ddr266 than your memory bus was clocked to the lowest speed.

if the lowest speed was 333Mhz than either you have quality issues with some of your memory or your motherboard is not detecting it properly. in that case you will have to manually adjust your memory frequency or be happy with slow memory.

dual channel is a gimmick. you get about 7-15% increase in memory performance. it is better to have the same speed memory in a sysem, but if your computer runs stable don't worry about it.
ekÆsine is offline  
Old 11-28-2003, 04:16 PM   #7 (permalink)
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Sorry if I was unclear...

I HAVE 3 sticks of memory, but they are not installed. I only have two slots on my board.

I finally made a decision and (like you advised) chose to use the combination of 128 and 256 MB, both at 333 MHz. However, as noted above, my computer says it's only at 266 MHz. Weird. I'm going to go home and try to alter the BIOS settings as 'sayboon' suggested and see if that helps.

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Old 11-29-2003, 06:02 AM   #8 (permalink)
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Not all board offer dual DDR capabilities.

This link explains the theory and your Mobo manual will tell you if it is supported.
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Old 11-29-2003, 05:23 PM   #9 (permalink)
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set your memory frequency to 166Mhz. you may have to set user defined settings first to allow the adjustment.
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Old 12-01-2003, 07:13 AM   #10 (permalink)
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To clear up confusion you may get with the guys saying set it at 166:

Your memory is 333 Dual Data Rate memory, that means its 166Mhz x 2 (thats where the Dual Data Rate terminology comes into it).

IMHO Memory is confusing stuff, I mean you have the base frequency (166Mhz), then the Dual Data Rate frequency (333Mhz), then you have the PC2700 etc value (could somebady say what is this called and what does it mean?), then you have dual channel mode (confusingly similarly worded to Dual Data Rate). Its no wonder an lot of people get confused over Memory.


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