SRAM vs DRAM: Difference Between SRAM & DRAM Explained

RAM, which stands for Random Access Memory, is a type of computer memory. A semiconductor device placed on a processor, it stores variables for calculations made by a CPU. In addition, RAM provides memory locations for registers, AKA requested information. First, the CPU receives a read instruction that includes the data’s memory address or location. Then, the computer communicates the address to the RAM controller. Subsequently, the read data gets transmitted back to a CPU cache.

This read/write operation is called timings. A computer with faster timings with less lag between them results in more immediate access times and less latency. Conversely, experiencing slower timings results in lower performance and higher latency.

RAM makes it possible to access any byte of memory without needing to access previous bytes. A volatile medium for storing data, RAM needs whatever device it’s on to be powered to access the memory and work.

There are two types of memory possible with RAM, SRAM, and DRAM.

DRAM, which is also known as Dynamic Random Access Memory, is a widely used type of RAM. It’s a memory chip that can hold large amounts of data but requires a lot of power.

SRAM, or Static Random Access Memory, is also a memory chip. It uses less power and offers better performance when compared to DRAM. That’s because DRAM needs to be refreshed while in use. SRAM does not need to be refreshed.

How both SRAM and DRAM are structured determines their main characteristics, pros and cons, and applications.

Static RAM (SRAM): Best used for:
SRAM is used for various types of electronics – anything from hearing aids to routers.

• CPU cache
• Hard drive cache
• Networking cache
• Scientific and automotive electronics
• Microprocessors
• Modern appliances
• Toys
• Computers
• Routers
• Peripheral equipment
• Portable and battery-operated equipment

Dynamic RAM (DRAM): Best used for:
DRAM is found in servers and used in computers’ main memory and graphics cards.

• System memory
• Connecting to a CPU bus
• Smartphones and tablets
• Laptops
• Digital electronics needing high-capacity memory
• Graphics cards

Table of Contents

• SRAM vs DRAM: Difference Between SRAM & DRAM Explained
  • Key Differences Between SRAM and DRAM
  • What is SRAM?
    • Structure of SRAM
    • Benefits of SRAM
    • Disadvantages of SRAM
    • 3 Types of SRAM
    • SRAM Pricing
  • What is DRAM?
    • Structure of DRAM
    • Benefits of DRAM
    • Disadvantages of DRAM
    • 5 Types of DRAM
    • DRAM Pricing
  • Can SRAM & DRAM be used together?
  • Bottom-Line: Difference Between SRAM & DRAM

Key Differences Between SRAM and DRAM

Learn more about computer memory: 9 Types of Computer Memory Defined (With Use Cases)

What is SRAM?

As long as it has power, SRAM retains data in its memory. Unlike DRAM, the need to continually refresh SRAM does not exist. Not needing to refresh is excellent because it means better performance as well as less power usage.

SRAM is commonly used for a computer’s memory cache. For example, they can be found in a processor’s L2 or L3 cache. Because of its cost and size, SRAM is not generally used for a computer’s main memory. However, you may find SRAM used as a buffer cache in a disk drive, a printer peripheral, or a network router or switch.

However, you can use SRAM for a variety of other purposes. As an example, SRAM might be part of a RAMDAC or a digital-to-analog converter on a computer’s video or graphics card.

SRAM can be found in many other devices, such as cell phones, tablets, and wearables. In addition, you can discover SRAM embedded in medical products, toys, appliances, automobiles, industrial equipment, and a wide range of IoT devices.

Structure of SRAM

SRAM is mainly used as a memory cache for a CPU. This type of semiconductor consists of flip-flops memory and uses bistable latching circuitry to store each bit. Data is stored using four to six transistor memory cells.

In an SRAM chip, each memory cell stores a digit in binary as long as power is supplied. Once a flip-flop stores a bit, it will keep that value until an opposite one is held. SRAM is relatively large, but it does give access to data quickly. In addition, SRAM is in the form of on-chip memory.

Benefits of SRAM

Both SRAM and DRAM have their advantages. However, when compared to DRAM, SRAM tends to be faster, with an access time as short as ten nanoseconds. Additionally, there is no need to refresh SRAM, like you constantly do with DRAM. SRAM also consumes less power than DRAM and only needs a steady, small current.

Disadvantages of SRAM

While SRAM has many benefits, SRAM also has a downside. SRAM tends to be more expensive, and it requires more chip space. There is less memory per chip, and they are harder to manufacture. The power SRAM consumes depends on the access frequency, so when SRAM is used at a slower pace, it draws almost negligible power when idling. However, SRAM will consume just as much energy at higher frequencies as DRAM.

3 Types of SRAM

The three types of SRAM modules are used to upgrade a system’s cache in older computers so that they can store more data. We’ve talked about what makes high speed possible is the SRAM above. Another reason SRAM tends to be fast is that it allows microprocessor access to other memory sources besides a hard disk.

SRAM has three modules:

1. Asynchronous static RAM: this SRAM was the first type ever made, and is usually used to offer an inexpensive upgrade to older machines. Upgrades may include memory or speed.
2. Synchronous burst static RAM: this type of SRAM is expensive but very fast.
3. Pipeline-burst static RAM SRAM: PBSRAM is the most commonly used SRAM today. After the first round of access, it’s designed to allow other access cycles to require fewer machine cycles, allowing for more data output.

SRAM Pricing

With all the speed and size benefits of SRAM, it’s no surprise that SRAM is much more expensive when compared to DRAM. While an SRAM cache costs around $5,000, a gigabyte or DRAM costs significantly less at around $50.

Because SRAM uses flip-flops, which can be made of up to 6 transistors, SRAM needs more transistors to store 1 bit than DRAM. If we compare, DRAM only uses a single transistor and capacitor. Thus, SRAM requires a higher number of transistors for the same amount of memory. All this increases the production cost.

Learn more about cache memory and how it works.

What is DRAM?

Dynamic random access memory (DRAM) is a type of semiconductor memory. DRAM is typically used for program code needed by a computer’s processor to work. However, you can also find DRAM on personal computers, workstations, and servers. RAM allows a PC processor to access any part of the memory directly rather than proceeding sequentially from a starting place.

RAM enables faster access to data compared to storage such as hard disks. RAM is faster primarily due to its location – close to a computer’s processor.

Structure of DRAM

DRAM is based on a 1T1C, or one-transistor, one-capacitor cell structure. The cells are arranged in a rectangular, grid-like array. A voltage is applied to the transistor in a DRAM cell. This voltage is then given a data value and placed on a bit-line. Once done, it charges the storage capacitor. Each bit of data is stored in a capacitor.

Over time, the charge in the capacitor tends to discharge when the transistor is turned off. That’s why the stored data in the capacitor must be refreshed every 64 milliseconds. DRAM requires less chip area because it has fewer components. Therefore, a DRAM chip holds more memory when compared to SRAM. In addition, DRAM has the characteristics of off-chip memory.

Benefits of DRAM

There are many advantages to using DRAM. Perhaps one of the most notable is the cost. The cost tends to be much lower when compared to SRAM. It also is quite simple in design, and the fact that it requires one transistor helps when it comes to the price point. Most computers use DRAM because it supports greater densities at a lower cost.

A DRAM also provides high-density levels and can store a lot of data. In addition, as long as DRAM is running, memory can be refreshed — and deleted.

Disadvantages of DRAM

Like SRAM, DRAM has advantages and disadvantages. When it comes to disadvantages, DRAM is slower than SRAM. DRAM requires little bursts of power every few milliseconds. It requires this power because it needs to refresh. This takes time, hence the reason why DRAM is slow. The average access time for DRAM is 60 nanoseconds, which comparatively, as we talked about earlier, SRAM’s access time can be around ten nanoseconds.

Another disadvantage to DRAM is that it actually needs power. Otherwise, you will lose data. DRAM also consumes more power when compared to SRAM.

5 Types of DRAM

1. Synchronous DRAM: this type of DRAM is used to sync CPU clock speeds with memory speeds. This lets the memory controller know the cycle of the CPU clock and allows the CPU to perform more actions simultaneously.
2. Rambus DRAM: this type of DRAM is a bit out of date. It was more widely used in graphic cards in the early 2000s.
3. Double Data Rate SDRAM: this type of DRAM almost doubles the bandwidth of synchronous DRAM because it uses double pinning. Double pinning allows data to transfer on rising and falling edges of a clock signal. DDR SDRAM has different iterations over time, including DDR2 SDRAM, DDR3 SDRAM, and DDR4 SDRAM.
4. Fast Page Mode DRAM:  this type of DRAM gives higher performance than other DRAM types by focusing on quick page access.
5. Extended data out DRAM:  this type of DRAM improves the time to read from memory on microprocessors, such as the Intel Pentium.

DRAM Pricing

When compared to SRAM, DRAM is much less expensive than SRAM. Part of the pricing is due to the pricing of their gigabytes. A gigabyte of DRAM will cost about $50, while SRAM can cost upwards of $5,000.

Learn more about DRAM and how it works.

Can SRAM & DRAM be used together?

With the differences being so huge between SRAM and DRAM, one may wonder if you can use both at the same time. The short answer is yes. Yes, you can use them both and, in fact, they complement each other. If the hardware incorporates both designs, there really isn’t a reason not to use them together. If you do use both, you’ll probably find that the RAM latency between the two can also be beneficial.

If you use both, the result is a memory system that acts as though it’s both inexpensive and fast. In short: you get the best of both worlds.

Bottom Line: Difference Between SRAM & DRAM

Static RAM, or SRAM, and dynamic RAM, or DRAM, are types of RAM. SRAM tends to have better performance with lower power requirements. However, SRAM tends to be much more expensive than DRAM. SRAM also takes up more space and is commonly used for a computer’s memory cache and is not used on a main memory due to its cost and size. SRAM also uses transistors, while DRAM uses capacitors and not many transistors.

Most computers use DRAM instead of SRAM, but SRAM is used for other purposes, such as a digital-to-analog converter on a computer’s graphics card.

Because of the differences between DRAM and SRAM, DRAM is better suited for main memory, and SRAM is better suited for a  processor cache.