Further musings and specs.
The next problem in evaluating DDR550 memory properly is in finding a motherboard that's able to hit 275MHz FSB/driven clock with utter stability. EPoX's S939-based 9NDA3+ answered the call.
A simple case of lower the multiplier on our AMD Athlon 64 3800+ and raising driven clock to the required 275MHz. HTT frequency was adjusted down to 4x from the default 5x. I've also chosen an overall clock speed of 2200MHz as we can directly compare this setup's performance against a 2200MHz/200MHz driven clock's.
One has the choice of limiting the memory clock with a 5:4 driven clock-to-RAM ratio. In evaluating the Corsair XMS4400, however, synchronicity was the key.
A 20-minute run of Memtest86+ confirmed the RAM was up to specification, as far as an nForce3 250 motherboard was concerned.
Official specification
512MB and 1024MB kits available
Implemented using 16 256MBit chips per module (1GB kit)
Samsung K4H560838F-TCCD chips (nominally rated at DDR500) on a custom Corsair PCB
100% tested at 275MHz (DDR550) on both AMD and Intel platforms
Lifetime Corsair warranty
Latency: 2.5-4-4-8 @ 2.75v
Let's now see what kind of job these high-speed modules make of our memory-dependant benchmarks.