You must be curious: mobile phone memory (RAM) often reaches 8G or 12G, but why do microcontrollers have less than 1M of RAM?
To understand, the classic AT89C51 microcontroller has only 128 bytes of RAM (memory). Similarly, the classic MSP430F149 also has only 2K of RAM space. Even the STM32F1 series, which is commonly used now, has a maximum RAM of less than 100K.
Thus, many friends have this question: now solid-state drives are measured in terabytes, mobile phones and computers have memories of 8G or even 32G, but why do microcontrollers have less than 1M of RAM?
Today, we will discuss RAM and the issue of low memory in microcontrollers (Note: the microcontroller referred to in this article is MCU microcontroller).
About RAM
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Random access -
Volatile -
Sensitive to static electricity -
Fast access speed -
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Reasons for Small RAM Capacity
Compared to Flash and hard drives, achieving a sufficiently large capacity for RAM is much more costly.
1. More Complex RAM Technology
RAM requires faster speeds and cannot draw too much current. To meet and balance these higher requirements, more specialized and advanced semiconductor capacitor technologies need to be used.
2. Larger Silicon Area
Because RAM technology is more complex, it occupies a larger silicon area.
Everyone knows the chip manufacturing process. Currently, chips are primarily made from silicon (although more advanced materials have been invented now), and a larger silicon area means that the cost of a single chip is higher; this principle is understood by everyone.
By understanding the relationships between wafer, die, and cell, you can roughly grasp that chips are actually generated in “batches”.
3. Power Consumption Reasons
Microcontrollers usually require low power consumption, especially low-power microcontrollers, which must operate in standby mode at the nA level.
To meet low power consumption, RAM in microcontrollers is usually static RAM (SRAM).
Here, it is worth expanding on DRAM (Dynamic RAM), which requires periodic refreshing of the stored charge due to leakage; DRAM thus requires driving circuits, which naturally leads to higher power consumption compared to SRAM.
4. Low Demand for Large Capacity RAM in Microcontrollers
As we all know, projects developed using microcontrollers are usually bare metal or RTOS, and large software is generally not used, especially in the early days (early projects with low RAM demand generally expanded RAM externally).
Therefore, many early projects did not have high requirements for microcontroller RAM capacity, and a significant portion of RAM was not utilized.
Of course, with the rapid development of UI, AI, and the Internet of Things, the demand for RAM in microcontrollers is also continuously increasing. Many new microcontrollers now have RAM capacities that are also increasing, such as 256K or even 512K.
5. Other Factors
In addition to the points mentioned above, factors such as lifespan, stability, and compatibility also indirectly affect RAM size.
Finally, everyone is welcome to add more reasons.
Source: strongerHuang
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