Tech Tip: What is a Bus Type?

Bus Type, also known as the Bus Speed, is tied with the Peak Transfer Rate and Peak Data Rate. This is very critical to consider when upgrading or adding memory to an existing machine. If the memory modules aren’t on the same page, it can lead to undesirable results.

Backwards Compatibility

You won’t find memory being compatible between generations. For example, a DDR4 module won’t work with DDR3 memory environment or vice versa. However, you may find that modules can be compatible within the same generation. A faster DDR3 module may run with slower DDR3 modules, the only caveat is that the system will only run at the speed of the slowest module. In this case, your machine will be limited to the slowest compatible memory you have installed.

To help you find the right one, each memory’s speed can be understood by either its ‘Friendly Name’ or its ‘Industry Name’.

Doing the Math

Each one of the bus speeds can be calculated and has a logical reasoning behind it. It’s more than just a cool number attached to a series of characters.

For example, you may find on the market a DDR3-1333 or a PC3-10600. Both of these are descriptions of its speed of the same module. DDR3-1333 actually runs at 666.6 MHz. It also performs two transfers per each clock cycle resulting in a transfer rate of 1333.3 MT/s (million transfers per second). Since DDR3 modules have 64 data pins, there will be 64 bits in each transfer (or 8 bytes per transfer).

1333.3 MT/s * 64 bits = ‭85,331 Mb/s (or 10,666.4‬ MB/s)

Conclusion

In conclusion, the ‘Friendly name’ of a DDR module is the Bus Transfer Rate in MT/s (Million Transfers per second). and the ‘Industry name’ is the rounded total bandwidth of MB/s (Megabytes per second). Be aware of DDR modules and how they’ll work with your sytem if you’re upgrading or adding memory. Next time you see a module in the wild, you can identify what the bus type is what and it means.

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