Is DDR5-8000 CL38 stable? Bleeding-edge Intel XMP and timings guide
DDR5-8000 CL38 is the bleeding edge of mainstream XMP memory in 2026, a speed grade that only works reliably in two-DIMM configurations (one DIMM per channel) on high-end Z790 / Z890 boards with strong memory controllers. The 9.50 ns first-word latency is essentially matched to DDR5-7200 CL34; the real story is bandwidth.
Calculator
RAM Latency Calculator
Timings are in memory clock cycles. True latency in nanoseconds is derived from the data rate.
True Latency
First-word latency (CL)
9.50 ns
Time from a read command to the first bit of data arriving.
I/O bus clock
4000 MHz
Cycle time
0.250 ns
tRCD delay
12.00 ns
tRP delay
12.00 ns
tRAS
24.00 ns
tRC (tRP + tRAS)
36.00 ns
Assumes one 64-bit channel. Dual channel doubles this, quad channel quadruples it.
How this is calculated
4000 MHz bus clock, 0.25 ns per cycle, 38 cycles of CL = 9.50 ns. Peak per-channel bandwidth is 64 GB/s, 11% over DDR5-7200 and 25% over DDR5-6400. Four-DIMM configurations almost always require backing off to DDR5-6400 or slower on this same platform, which is why enthusiast builds targeting 8000 MT/s universally use 2× 24 GB or 2× 48 GB kits rather than 4× smaller modules.
Verdict
DDR5-8000 CL38 is for enthusiasts with a good IMC-bin CPU and a 2-DIMM board. The gains over DDR5-6400 CL32 are real but modest in games; it matters most for memory-bandwidth-bound synthetic workloads.
More DDR5 scenarios
Frequently asked questions
Is DDR5-8000 CL38 worth the price premium?
Can you run four sticks of DDR5-8000 CL38?
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