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I have an old Dell 640m which I desperately want to upgrade the RAM of. It currently contains these memory modules (a total of 1GB running at 533MHz). I have found the User Manual which (on page 158) states the following:

Memory module connector: two SODIMM connectors
Memory module capacities: 256 MB, 512 MB, 1 GB, and 2GB
Memory type: 1.8-V SODIMM DDR-2
Minimum memory: 256 MB
Maximum memory: 2 GB

but how can I determine the maximum RAM speed that it can support?


Although I have searched online for this, I have found conflicting information, some even stating its maximum ram capacity is 4GB


I just ran $ dmidecode -t 16

# dmidecode 2.9
SMBIOS 2.4 present.

Handle 0x1000, DMI type 16, 15 bytes
Physical Memory Array
        Location: System Board Or Motherboard
        Use: System Memory
        Error Correction Type: None
        Maximum Capacity: 4 GB
        Error Information Handle: Not Provided
        Number Of Devices: 2

so would that be more trustworthy than the manual, or is that a fallback value?

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According to Dell this system only has two memory slots. Are you sure it's a 640m? – danielcg Feb 14 '13 at 1:39
yes... it says so on the side. and that is the number of memory slots stated Memory module connector: two SODIMM connectors – topherg Feb 14 '13 at 1:41
"I have an old Dell 640m which I desperately want to upgrade the RAM of. It currently contains these memory modules" – danielcg Feb 14 '13 at 1:48
upgrade, as in replace. whats your point? – topherg Feb 14 '13 at 1:50
up vote 2 down vote accepted

according to, all the memory they list as compatible is DDR2 PC2-5300 • CL=5 • Unbuffered • NON-ECC • DDR2-667

So it looks like 667 is the only option.

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but they state the maximum ram capacity is 4gb, so i trust that site as far as i can throw the hardware connecting me to it – topherg Feb 14 '13 at 1:35
it appears that website might have merit, in which case, if I install 667 RAM, and it turns out the maximum it can support is 533, will it default to 533 or fail entirely? – topherg Feb 14 '13 at 1:58
I would trust crucial, if they say it supports 667, it does. – Keltari Feb 14 '13 at 2:06
yes the max is 4gb, so you could get 2x2gb sticks – Keltari Feb 14 '13 at 2:07
@cgoddard: For modern RAM, the stated clock speed is the maximum clock speed. It can run just fine at a lower clock speed and you will usually still get at least some of the benefit of the lower latency that faster RAM has (assuming all your RAM is the same). So, all other things being equal (cost, latency cycles, etcetera), you should buy 667MHz RAM. – David Schwartz Feb 14 '13 at 4:24

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