So as far as I understand Random Access Memory lets us access any stored in it data regardless where it’s stored and with the same speed.
I just don’t understand what makes that physically possible. Data is being transfered through electrons at approximately the speed of light through the wires. But how do you connect the wires to access all of the data everywhere in RAM at the same time?
Is the data being broken down into bits over all the RAM units – making the data collection process longer as you have to gather all the data particles or is there something I’m missing.
If I got any of my facts wrong feel free to correct me.
In: 7
First the speed of light is largely irrelevant here. The data is accessed at the same speed for all practical purposes.
Having a section 3mm further away take longer is more of a scientific technicality than a practical difference.
That said, RAM does not necessarily operate at the speed. A common example is laptops with 12GB of RAM – they use an 8GB and a 4GB module.
Part of RAM’s high speed is parallelism. The 4GB stick will be parallel to 4GB in the 8GB stick and they’ll work together in dual channel to achieve full speed.
4GB will remain in single channel and will be slower.
RAM also operates on a complex bus system that will nullify many of these technicalities.
I like to compare it to a subway/metro train system. For example if all the data has to get on a subway car and travel to the CPU, it doesn’t matter if they enter slightly faster or slightly slower because everyone on the train reaches the next station at the same time.
There are many kinds of latencies and delays and steps along the way. From paying, to getting a ticket, to the time it takes for the doors to open and shut, to the travel time.
For example an AMD CPU might have an infinity fabric speed of 1,600 MHz with 3,200 MHz RAM. Here the RAM will dump two train loads of data at the I/O die’s memory controller, and then transfer onto a new train to the CPU. Maintaining this 2:1 ratio yields optimal performance.
Lastly, RAM traces on motherboards have zig-zags in them to maintain constant length to help with high speed signal integrity:
https://preview.redd.it/kkor7dcawu751.jpg?auto=webp&s=60a299a2d44a54a2fc975a9caa9ebcbda3bb16e8
These are carefully planned so all the traces are the same length.
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