Faster memory for PCs: DDR5-8800 specified

There are six new clock speeds for DDR5 memory. The JEDEC Solid-State Technology Association has now re-specified DDR5-6800 to DDR5-8800 – previously the maximum was DDR5-6400. For users of desktop PCs and notebooks, this primarily means that AMD, Intel and ARM chip designers will be able to release faster SDRAM for their processors in the future.

The companies will adhere to the officially specified clock speeds, depending on what the integrated memory controllers can handle. Apart from the JEDEC specification, 8400 series bars from G.Skill have been freely available since the beginning of the year. They count as overclocking modules that do not adhere to the JEDEC specifications and run at a higher voltage.

Stability before performance

JEDEC stipulates significantly laxer timings for maximum stability. The organization differentiates between the three classes A, B and C. A still has the best timings of the three with 62-62-62 (CL, tRCD, tRP). This means that the SDRAM continues to operate mathematically at a CAS latency of 14.09 nanoseconds. JEDEC has previously targeted values of around 14 ns for all DDR5 levels.

Specified DDR5 clock speeds (JEDEC, Class-A timings)
Clock Rate	CAS-tRCD-tRP-Timings	CAS Latency (ns)	Transfer Rate (GB/s)
DDR5-3200	22-22-22	13,75	25,6
DDR5-3600	26-26-26	14,44	28,8
DDR5-4000	28-28-28	14,0	32,0
DDR5-4400	32-32-32	14,55	35,2
DDR5-4800	34-34-34	14,17	38,4
DDR5-5200	38-38-38	14,62	41,6
DDR5-5600	40-40-40	14,29	44,8
DDR5-6000	42-42-42	14,0	48,0
DDR5-6400	46-46-46	14,38	51,2
DDR5-6800	48-48-48	14,12	54,4
DDR5-7200	52-52-52	14,44	57,6
DDR5-7600	54-54-54	14,21	60,8
DDR5-8000	56-56-56	14,0	64,0
DDR5-8400	60-60-60	14,29	67,2
DDR5-8800	62-62-62	14,09	70,4

In practice, this only means an increase in the memory transfer rate to 70.4 gigabytes per second and latch. Typical desktop processors such as the Ryzen 7000 or Core i-14000 would achieve just under 141 GByte/s in dual-channel operation with two latches. Octo channel systems, for example with AMD's Ryzen Threadripper Pro 7000, can look forward to 563 GByte/s and would therefore already be at the level of mid-range graphics cards.

Meanwhile, the aforementioned G.Skill kits with DDR5-8400 clocks have 40-52-52 timings and thus achieve a CAS latency of just 9.5 nanoseconds. However, with a price tag of at least €7.70 per gigabyte (starting from 842 €), the kits are hardly affordable.

Against rowhammer attacks

Meanwhile, JEDEC has also included a new technology in the adapted DDR5 specification JESD79-5C. Per-Row Activation Counting (PRAC) sounds like a technique to prevent Rowhammer-type attacks:

"PRAC precisely counts DRAM activations on a wordline granularity. When PRAC-enabled DRAM detects an excessive number of activations, it alerts the system to pause traffic and to designate time for mitigative measures. These interrelated actions underpin PRAC's ability to provide a fundamentally accurate and predictable approach for addressing data integrity challenges through close coordination between the DRAM and the system."

However, halted data traffic also necessarily means that the technology will cost performance.

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(mma)