r/Alienware • u/Desk_Admirable • 55m ago
Discussion Area 51 Desktop Intel 285k Owners, performance and how to increase it.
**TL;DR**
* If you've got the 285K Area-51 with Dell's 64GB 6400 kit, XMP Profile 1 runs the memory in Gear 4. Turning XMP *off* is actually faster for the CPU. Free, two minutes, zero risk.
* I then went a lot further and got the same sticks running 6400 in Gear 2 with tighter timings, using settings Dell hides. Memory latency went from about 114 ns to 90 ns and my Time Spy CPU score from around 16,400 to around 19,800.
* Happy to stick everything on GitHub if people want it.
**The sorry saga**
Dell does not allow us to set Intel200S!
I bought an Area-51 recently (AAT2250, Core Ultra 9 285K, RTX 5090, 2x32GB Dell/Kingston DDR5-6400, Dell part XN09RP). Lovely machine, but the benchmarks never added up. My first clean Time Spy CPU score was around 16,400. On 3DMark that beats roughly 12% of people with the exact same CPU and GPU. Bottom of the class, on a PC that costs what this one does.
Talk about an insult.
I spent a couple of weeks on the CPU side first: power limits, undervolting, the lot. Nothing moved it.
**What it turned out to be**
Open CPU-Z and look at the Memory tab. With XMP Profile 1 on, mine showed the DRAM at 3192 MHz and the memory controller at 798 MHz. That's Gear 4, where the controller runs at a quarter of the memory speed. It's the slow mode, normally kept for very fast kits that can't run any other way.
Turn XMP off in the BIOS (F2, Performance, Extreme Memory Profile, pick Default DIMM Profile) and you get 5600 in Gear 2, with the controller at half speed (about 1397 MHz).
On mine:
* XMP 6400, Gear 4: about 114 ns latency, Time Spy CPU between roughly 16,400 and 17,000
* Default 5600, Gear 2: about 106 ns latency, Time Spy CPU around 17,900
To be fair to XMP, raw bandwidth is a bit higher with it on (about 91 vs 83 GB/s). But latency and every CPU-bound number I tried were better on plain old 5600. Bit mad really.
**Going further (this part is at your own risk)**
Dell's BIOS is built on Intel's, and all of Intel's memory options are still in there, just hidden. Windows isn't allowed to write to them, but a UEFI shell on a USB stick at boot is. That let me set a custom memory profile that Dell's menu doesn't show: speed, gear, timings and DIMM voltage.
I worked up in small steps over a few days:
* 6000 Gear 2, CL38-40-40: about 95 ns
* 6400 Gear 2, CL46 (Dell's own XMP timings, just in Gear 2 this time): about 96 ns
* 6400 Gear 2, CL40-42-42 at 1.25 V with the refresh interval doubled: about 90 ns
Time Spy is now just over 40,000 overall, with a CPU score of around 19,800. That overall score is in the top 9% of all 5090 results on 3DMark. My first run on this PC was below the median. And the CPU score is finally above the average for a 285K with a 5090.
Reality check: games at 4K barely move, because they're waiting on the GPU. Cyberpunk with path tracing went from about 71 to 72.5 fps. This fixes the CPU side, it doesn't buy you a new graphics card.
Stability so far: 9 hours of y-cruncher overnight, and 90 minutes of FurMark and y-cruncher together with the DIMMs sat at 78C. No errors.
**Things I learned the hard way**
* Ask these sticks for more than 1.25 V and the PC won't start at all (2 amber, 4 white blinks). 1.30 V and 1.35 V both did it. I still don't know why.
* Dell's RTC reset (PC off but plugged in, hold the power button for 25 seconds) wipes the hidden settings and got me back every time. It saved me twice.
* The sticks are made by Kingston and look identical to the retail FURY Beast 2x32GB kits. Kingston's datasheet for the retail 6000 kit is here: https://www.kingston.com/datasheets/KF560C40BBK2-64.pdf It's a handy sanity check on what's normal for these chips, but the Dell ones are only rated for their own XMP (6400 CL46 at 1.2 V), so don't assume the retail timings will just work.
* The doubled refresh interval is outside what any manufacturer ships. It tested clean here, but it's the one change I'd tell people not to copy blindly.
**Caveats**
* This is one machine, on BIOS 1.21.0. I've stopped updating the BIOS, because Dell has closed this sort of thing with updates on other models.
* It needs Secure Boot off to boot the USB shell, and I doubt it does your warranty any favours. If you break yours, that's on you.
* The simple fix (XMP off) has none of these risks. Start there.
**What I'd love to know from you lot**
* What does CPU-Z show on yours with XMP on, and which BIOS version are you on?
* Anyone on a newer BIOS: is it still Gear 4?
* Anyone with the 7200 CUDIMM kit, or an Aurora: what gear do you get?
* Has anyone got more than 1.25 V working on these sticks, or know why it refuses?
* Anything else you've found. I'd rather share this than sit on it, and I'm sure some of you know things I don't.
If there's interest I'll put the lot on GitHub: my notes, the map of the hidden settings, the scripts (they refuse to write anything unless the BIOS matches what they expect) and the memory test I used.
Credit where it's due: I did the firmware digging and the scripting with a lot of help from Claude. I'm not that clever by myself.
