Ram 1Gb v's 768mb

  BigAl127 12:38 06 Sep 2004

I currently have 768mb (1x 256mb & 1 512mb) of PC2100 ram in my 2.4Ghz pentium 4 computer.
A friend says by having 2 different size ram sticks in, i'm losing performance, and would be better upgrading the 256mb stick to a 512mb stick giving me 1Gb.

Now, I know that 1Gb has got to be better than 768Mb, but is my friend right about the layout in general?

  Diodorus Siculus 12:44 06 Sep 2004

Not really - if you have the larger stick in the first slot, and the smaller in the second, you will have adequate performance.

  wee eddie 16:03 06 Sep 2004

Yours are both of the same speed - PC2100.

If they were of different speeds, both would operate at the speed of the slower.

  BigAl127 16:58 06 Sep 2004

He was definitely referring to size rather than speed. Basically he said the following:-

1 x 64mb and 1 x 128mb Run well together

1 x 128mb and 1 x 256mb smallish loss in performance

1 x 256mb and 1 x 512mb quite a loss in performance.

i.e. the greater the difference in size of sticks, the greater the performance loss, is my understanding of what he was saying. Which would mean a 1 x 1gb and 1 x 512mb would give an even greater loss of performance.

  Diodorus Siculus 17:04 06 Sep 2004

How does he work this out? It doesn't seem to be very intuitive...

  Dorsai 18:04 06 Sep 2004

I think what your friend is refering to may be true, but his interpretation not too accurate. But it goes beyond my knowledge, and then some.

I managed to find a doc from intel, which does not directly relate to your system, at was about DDR ram with FSB speeds of 400Mhz and above, but it may apply in a broard sence.

What i think it said was that if Dimm 1 and Dimm 2 are both used, but by different sized Dimms, the mobo access the memory in 'single channel mode' (what ever that is).

If only one slot is used, or both slots have the same sized dimm in, the mobo runs in 'double channel mode' (ditto).

Double channel does sound like it should be faster than single channel...But by how much (Double i guess)?

As you dont say which mobo you have, i cant be sure it applies, as i don't know what chipset the mobo uses to access memory, so can't try and search more accuratly.

  bremner 19:45 06 Sep 2004

Dual channel DDR as described by Dorsai would result in poor performance with two different size Dimms.

However there will be no deterioration in performance on a single channel set up like yours.

Your friend appears to be mixing the two systems up.

  BigAl127 21:14 06 Sep 2004


According to Belarc Advisor my board is a Trigem computer, inc. Imperial 1.10

The BIOS: Phoenix 6.00 09/12/2002

The system I have is an E-Machines 770

Hope the above helps you find me an answer.

  bremner 22:47 06 Sep 2004

"but is my friend right about the layout in general?"

No - he/she is mistaken that you are losing performance.

Of course you would be better with 1GB if you have Windows XP.

  sedgi 23:17 06 Sep 2004

I was also running same, but pc2700 768mb (1x 256mb & 1 512mb). I noticed no drop in performance but no increase when I added the 512, I`ve removed my 256 stick recomended by a friend, runs much better and have ordered another 512 to go 1gb. For £40-£50 it would be worth it.

As my friend explained to me, If he is correct, when having your memory set this way you are not getting any increase in performace because you still only process through 256mb, and if you turn things around you bottle neck 512 won`t fit through 256, take out the 256 and you get the full benefit of 512mb.

  TomJerry 23:22 06 Sep 2004

If the motherboard support dual-channel memory, memeory stick should be in matching pair. So your friend is right for this, but I do not think your motherboard support dual channel memory, so your friend's comment on your machine is wrong.

There are some tests on performance impact of memory, any performance increase beyond 512MB is very very small in many lab tests. In some tests, big memory even reduce performance.

Maybe you could borrow your friend's memory stick and benchmark your PC to find out.

Personally, do not bother with it.

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