It is a form, speed and type of memory.
PC5300/PC5400 667MHz SODIMM Chip will be compatible for the Dell Inspiron 1721.
One can purchase 2GB DDR2 667MHz, at several online sites. Some of these online sites that carry this memory are "Amazon", "eBay", "Tigerdirect", and "Newegg".
Obviously the difference is speed.
DDR2 667MHz
it depend on your computer type,max ram that your computer can support
You can use 240-pin DDR2 667MHZ. And this mother board supports dual channel.Hope this helps.
667 MHz is a frequency that can be applied to computing, wave mechanics, or engine cycles. Hertz or Hz is a unit of measurement that measures frequency (for example an engine that rotates at 15 revolutions per second has a frequency of 15Hz). MegaHertz (MHz) is equal to One million Hertz, so one million times per second. I believe that you are asking in terms of computing because 667Mhz is the common speed of PC5400 DDR2 memory. This is a modern type of computer memory, so rest assured that it will suit your needs (i am assuming that you are looking to buy memory). The best brands to buy memory are: * Kingston * Corsair * Patriot * OCz
As long as they're the same type (DDR2, DDR3). The speed of the RAM should either be the same or higher than your original since the computer matches all installed RAM to the lowest speed. e.g. my computer currently has a 2GB 800MHz DDR2 as well as a 1GB 667MHz DDR2. But the RAM is set to 667MHz and isn't utilising the full 800MHz on the 2GB.
2 dimm 2gb RAM comes with 2 1gb modules. 4 dimm 2gb RAM comes with 4 512mb modules.
I believe so but it'll downgrade to the lowest one.
Yes. They are backwards compatible. Even with the installed 800MHz ram It will still only run at 667MHz speeds.
DDR and DDR2 slots are different (different pin density and different notch location). Putting a DDR2 stick in will be impossible, and even if you did manage to jam it in, it wouldn't work. Stick to what the tech support people tell you and it'll work just fine.