Memory help

[Kakin]

I got a dell 8400 from my work place and planning to upgrade this to my main computer at home. It’s a 3.4ghz Pentium 4 HT. I opened the heatsink and couldn’t find out which 3.4ghz was it. From Tom’s Hardware’s website there are 3, (E550, E650, and E651)
One poor thing is this computer only have 512mb of memory, as per dell I can only upgrade to 400 or 533 mhz DDR2. From Crucial, I can use either PC2 4200, 5300 or 6400. On Pricwatch.com the 2gb Kit are all the same price which from $45 to $50. Here are my questions. Can I downgrade my memory from PC2-6400 to maintain to the computer’s need and keep the PC2-6400 for future usage(http://www.newegg.com/Product/Product.aspx?Item=N82E16820220144 This just have a $40 MIR)?
Anyone know what CPU I have?
Thank You!

[Kakin]

Just spoke to Dell's representative, they say only can use up to 533mhz(pc2-4200). I am sure I can use PC2-6400, but just want to get 100% before I get that 15% restocking fees if not right. Any feedback will be appreciated!

[llChaosll]

From what I know, the 6400 could be used it would just be underclocked to whatever the board uses, but Im not 100% sure. So don't take my word on it.
As long as its DDR2 Memory & a DDR2 CPU & MB.
GL! :)

[Kakin]

Just ordered this, will see....
http://www.newegg.com/Product/Product.asp?Item=N82E16820220144

[jason4207]

You should have ordered RAM rated for 1.8v operation. Those you linked are rated for 2.2v operation, and I doubt that Dell will allow you to set the DRAM voltage manually. However, since you are underclocking them quite a bit they may operate just fine at 1.8v.

[Kakin]

Just installed the ram yesterday at 1am and worked fine. I checked the bios, all memory run at 400mhz. If I just have these new pair of memorys it will run on 533mhz. I thought what the heck with that 133mhz, so put every memorys together to make 2.5GB. I put the new 2GB memory in the first bay on motherboard and the old one 512mb in the second bay, hopefully it use the 2gb first when using computer...

[grndragon57]

If you put in the 512mb 400mhz you will loose dual channel also all your memory will run at the speed of the slowest stick. Leave out the 512mb it will run at 533mhz in dual channel.

[Kakin]

The 512 is 2x256mb dual channel. Is it worthed for an extra 133mhz vs more memory? I thought more memory is faster...

[grndragon57]

With 3 Sticks of RAM none of them will run in dual channel. 2gb 533mhz dual channel will be faster than 2.5gb 400mhz no dual channel.

[Kakin]

With 3 Sticks of RAM none of them will run in dual channel. 2gb 533mhz dual channel will be faster than 2.5gb 400mhz no dual channel.

All the memorys are dual channel. 2 sticks for 512mb with 400mhz and 2 sticks for 2 GB with 800mhz. I wish I can crack the dell's bios and make it run 800mhz, so I can only put 2gb down.

[jason4207]

You're running dual-channel, so don't worry about that. 2.5GB is only better than 2GB if you're system is using more than 2GB at any given time. Are you running XP or VISTA. VISTA uses a lot more RAM than XP, but even in VISTA I've yet to use much more than 1GB, much less 2GB of RAM. I only run VISTA to play Bioshock, though, so my experience may not be typical.

On my work PC I have seen RAM usage climb into the 1.7GB range if I leave Firefox open for several days, and have several AutoCAD drawings, Excel spreadsheets, PDFs, and various other windows open. Firefox can eat up some RAM if left unattended. I only have 1GB on my work PC, so I am forced to shut-down un-used programs, or just re-start Firefox to eliminate the virtual memory lag.

Bottom-line: 2GB is plenty, and the faster speed will give a slight performance boost. If you find you're using more than 2GB then pop those other 2 sticks in.

* to see RAM usage pull up the task manager. On the bottom it says "Commit Charge: xxxxM/xxxxM". The left number is your RAM usage. If it ever climbs above 2048M then you may want more than 2GB RAM.

[Kakin]

I test the computer with both 2gb + 512mb or 2gb by itself and the reading for 3dmark06 is 4260 vs 4261 and cpu 933 vs 938 respectfully. After a week of observation, I always have 1.5gb left on memory. I took the 512mb out. Thanks for the advice. :)