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I used this question to calculate if RAM from an old system will work in a new system; it seems to me that it won't work.

The old system has a CPU with an FSB of 533 with DDR2 RAM, resulting in an Effective Speed of 2.1 GHz.

The new system has a CPU with an FSB of 800 with DDR2 RAM, resulting in an Effective Speed of 3.2 GHz.

The effective speed of the RAM for the new system is faster than the Effective Speed of the RAM for the old system, and thus the RAM from the old system will not work in the new system correct?

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leeand00
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  • whats the factory frequency of the ram? – Uğur Gümüşhan Jul 11 '16 at 14:48
  • Do you mean the RAM Speed? 667 MHz – leeand00 Jul 11 '16 at 14:50
  • how can it be 667 if it's ddr 2? https://en.wikipedia.org/wiki/DDR2_SDRAM#Chips_and_modules – Uğur Gümüşhan Jul 11 '16 at 14:54
  • leeand00's question is quite relevant. RAM speed is not the same as CPU speed. Give it a try! The really big gotcha that many people are unaware of is that you don't want to be mixing different speeds of RAM chips. However, if all of the RAM chips work together now, they likely will there too. RAM manufacturers have done a relatively decent job of making incompatible RAM not fit. They haven't done a perfect job at this, there may be exceptions, but my vague understanding is that's usually been true (in the recent days, ever since DDR). – TOOGAM Jul 11 '16 at 14:56
  • I typed the service tag into Dells website... http://www.dell.com/support/home/us/en/19/product-support/servicetag/9HXKDH1/configuration Under Original Configuration -> Components I found the following: - 223-6623 : OptiPlex 740 Minitower, Athlon 1640B (2.7GHz,512KB) - INSTRUCTION, DEVIATE-TO-MSMT-L5.5, Pentium M Dothan, 1.73GHZ, 2 MEGB, 533FSB - 311-6446 : 4GB,Non-ECC,667MHz DDR2,2X2GB Dell OptiPlex 960 – leeand00 Jul 11 '16 at 14:58
  • So the front side bus is listed as 533, and the RAM is listed as 667MHz, unless I'm looking at the wrong variables. – leeand00 Jul 11 '16 at 14:59
  • tell me what your cpu is (in detail, dont just say i5 or something) and ill give you a correct answer in minutes – Uğur Gümüşhan Jul 11 '16 at 15:01
  • @UğurGümüşhan The old one the new one or both? – leeand00 Jul 11 '16 at 15:02
  • @leeand00 all info you can provide – Uğur Gümüşhan Jul 11 '16 at 15:03
  • The old one is: an Athlon 1640B. – leeand00 Jul 11 '16 at 15:05
  • The "new" one is either one of these two: – leeand00 Jul 11 '16 at 15:08
  • - PROCESSOR, 80547, PENTIUM 4 PRESCOTT DT, 640, SKT-T, MALE – leeand00 Jul 11 '16 at 15:08
  • - PROCESSOR, E4400, 2.00, 2M, CORE DUO-CONROE, M0 – leeand00 Jul 11 '16 at 15:08
  • be specific. use msinfo32.exe – Uğur Gümüşhan Jul 11 '16 at 15:09
  • The old one has Windows installed on it; I'll have to see about the other ones... – leeand00 Jul 11 '16 at 15:11
  • From msinfo32.exe: `AMD Athlon(tm) Processsor 1640B, 2700 Mhz, 1 Core(s), 1 Logical Processor(s)` (for the old one) – leeand00 Jul 11 '16 at 15:17
  • your 666 ram wont work on intel p4 prescott nor on intel core duo, you'll need a 800 mhz ram and that is "PC2 6400" or above" – Uğur Gümüşhan Jul 11 '16 at 15:21
  • @UğurGümüşhan Did you determine this the same way that I did? – leeand00 Jul 11 '16 at 15:23
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    a ram can support multiple frequencies, you told me it's 666mhz so your ram is PC2-5300 which is below pc2-6400. your ram supports 666mhz max. your fsb will not run below 800, you can still try to change your FSB to 666 through bios I dont think it will work – Uğur Gümüşhan Jul 11 '16 at 15:27
  • Do not specify processor type (the new one), specify MOTHERBOARD or computer model like Optiplex 740, HP ProBook 450 etc . – Vojtěch Dohnal Jul 19 '16 at 12:10
  • This question makes no sense at all. All of the CPUs being discussed have on-die memory controllers and no FSB. – David Schwartz Nov 03 '16 at 19:03

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your ram is pc2-5300 ~666mhz and your cpu is designed to work with pc2-6400 ~800mhz or above so I don't think your ram will work with your pentium 4 cpu.

You can still try lowering the fsb through your bios. I wouldn't touch it.

If you wanna make sure you reported the correct speed of your ram, you can install hwinfo64 and check the frequencies supported by your ram. It's a window like this.

enter image description here

Uğur Gümüşhan
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Both the question and the accepted answer contain egregiously wrong information.

As deduced from the comments, you have a Dell OptiPlex 740 with AMD Athlon 64 1640B. However the component list in the product support webpage erroneously includes Intel Pentium M Dothan 740, which is simply ridiculous, as you cannot have both AMD and Intel CPU in one PC.

Since this Intel CPU has 533 FSB, you mistake this as the FSB of your AMD CPU. In fact, the talk of FSB for AMD is inappropriate as AMD has a dedicated Memory Bus which allows your RAM to run at speed independent of the FSB.

So does this mean AMD is superior as RAM speed is reliant on FSB for Intel? Not exactly!

Because the method you quoted and used to determine RAM speed is also wrong. There is something called Memory Divider which allows the RAM to negogiate with Motherboard in order to run at full speed, and it usually works.

To put it simply, your DDR2-667 RAM will run at full speed, as it is the general standard for DDR2-compatible motherboard.

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