Modern computers need to have RAM installed on RAM sticks.
This wasnt always the case, though, as DIMMs were invented in the 1990s.
Because many chips were needed, a lot of space was taken up.
TheSingle In-line Memory Module or SIMMwas designed to free up most of that space.
The memory chips were installed on a separate circuit board and plugged into the motherboard at a perpendicular angle.
The first generation of SIMMs used electrical pins that went into sockets like a large SIP chip.
To reduce costs and increase the integrity of the connectors, the pins were redesigned to be edge connectors.
These edge connectors are still used in modern DIMMs, albeit with some modifications.
The thing about these new edge connectors was that they went over the whole bottom edge.
Each connector pad ran over the SIMMs front, bottom, and back.
The overall number of connectors didnt change, just the punch in.
This is the key difference between SIMMs and DIMMs.
On SIMMs, the connectors are redundant on either side because theyre really one pin.
The connectors on DIMMs are different on each side, doubling the pin count with no extra effort.
Note:Slightly confusingly, these edge connectors are still generally referred to as pins.
Adding more pins means more data can be transmitted per clock cycle, increasing the bandwidth.
Not all of the pins go into improving the actual I/O bandwidth of the SIMM.
A range of pins is used to issue commands to the RAM too.
When CPUs process data, they need that data to be in the CPU cache.
That cache is significantly faster than RAM but much more expensive, so theres not much of it.
So, data is stored in RAM and then copied to the cache when needed.
This means that as many bits as possible can be transmitted per clock cycle.
As CPU development continued, the memory bus width was increased to 16-bits.
SIMMs were paired up to get around this, providing 16 data pins to fill the memory bus.
Of course, CPU development didnt stop there, and the 32-bit memory bus soon came along.
While some systems supported dual 72-pin SIMMs, a new form factor took the lead, DIMM.
Eventually, the DIMM form factor became the standard, and SIMM dropped out of use.
Essentially nothing still uses SIMM now.
Indeed no new hardware.
However, there are almost certainly legacy devices still running it somewhere.
DIMM is still used today and is unlikely to go anywhere soon.
Conclusion
SIMM was the original form factor for the memory stick.
