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Can I calculate the maximum bandwidth of DDR RAM myself?


Calculate the maximum bandwidth of the DDR RAM yourself, scenarios correctly thought out and nicely worked out with examples:



PS:
These values ​​are only achieved when writing/reading a 64 bit or 32 bit value! However, it only makes sense if values ​​are reset, e.g. with the ZeroMemory command.

Question about measurement results in ► ►  ... IsMyMemoryOK

1. Scenario 1: DDR4-3200 in dual-channel mode
2. Scenario 2: DDR5-4800 in single-channel mode
3. Scenario 3: Overclocked example
4. Calculating back from GB to MHz ;-)
5. Important notes:



The bandwidth values ​​shown refer to the theoretical maximum performance under ideal conditions, especially when reading or writing data linearly. These conditions are often observed in special scenarios such as resetting memory with functions such as ZeroMemory or memset. 


1.) Scenario 1: DDR4-3200 in dual-channel mode



- Clock:
3200 MHz

- Transfer rate per clock:
64 bits

- Channels:
2 (dual channel)

Calculation:
(3200MHz × 64Bit × 2) / 8 = 51,200MB/s

or directly to GB with 3.2 GH and the factor
(64Bit × 2 = 128Bit / 8) = 16
16 * 3.2 = 51.2 GB

Maximum bandwidth:
51,200 MB/s (or 51.2 GB/s)




2.) Scenario 2: DDR5-4800 in single-channel mode



- Clock:
4800 MHz

- Transfer rate per clock:
64 bits

- Channels:
1 (single channel)

Calculation:
( 4800MHz × 64Bit × 1 ) / 8 = 38,400MB/s

Maximum bandwidth:
38,400 MB/s (or 38.4 GB/s)




3.) Scenario 3: Overclocked example



- Clock:
2133 MHz (overclocked to 2800 MHz)

- Transfer rate per clock:
72 bits (unusual, but assumed)

- Channels:
2 (dual-channel)

Calculation:
( 2800MHz × 72Bit ×2 ) / 8 = 47,040MB/s

Maximum bandwidth:
47,040 MB/s (or 47.04 GB/s)




4.) Calculating back from GB to MHz ;-)



Measured value:
51.2 GB/s

Calculation:
51.2 GB/s / 16 = 3.2 * 1000 = 6400MHz

For dual channel:
3200MHz / 2 = Two 3200 DDR4 RAM modules in the dual channel

For single channel:
This would mean one DDR5 6400 RAM module in the single channel

This gives you a good understanding of the bandwidth calculation based on clock frequency, bus width and channels!

Value 8: 8 bits = 1 byte

64 bits for  single channel are then 64 * 1 = 64 bits 

64 bits for  dual channel are then 64 * 2 = 128 bits 

64 bits for  triple channel are then  64 * 3   = 192 bits 


5.) Important notes:




- Theoretical maximum bandwidth:
These values ​​represent the theoretical bandwidth. In practice, the actual bandwidth can be affected by factors such as memory latencies, processor architecture, and software.


- Bus width:
Both DDR4 and DDR5 have a bus width of 64 bits per channel. DDR5 differs in its architecture, which uses two 32-bit channels per module, but the effective bus width per channel remains 64 bits.



FAQ 5: Updated on: 6 October 2024 14:49 Windows

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Can I calculate the maximum bandwidth of DDR RAM myself?


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