AMD Expo 1.2 Expected To Bring Faster Memory Overclocking & CUDIMM Support
Because of the way we interact with these features, it's easy to think of Intel XMP and AMD EXPO as binary, 'yes or no' features, but both standards have actually gone through a few revisions. Right now, we're on revision 1.1 of AMD's EXPO, but it looks like 1.2 is on the horizon, and we know that because it has just appeared in the patch notes for critical system monitoring utility HWiNFO. However, that in itself is perhaps not as interesting as what it represents for the future of AMD's processors.
First, the concrete news: HWiNFO version 8.35-5890 Beta is out, and it improves the already-included support for Intel's Nova Lake, it fixes several bugs, it adds a new stress test tool, it adds NPU sensor monitoring for AMD and Qualcomm chips, and it improves support for LPCAMM2 modules—all good stuff. Down near the bottom of the list is a simple note that the new version adds EXPO 1.20 support; there's not much to go on based on that.
However, on Xwitter, famed memory overclocking expert 1usmus (author of the Ryzen DRAM Calculator) explained that EXPO 1.2 is about adding support for CUDIMMs. If you haven't been keeping up, CUDIMMs are DDR5 memory modules with integrated clock drivers; this allows them to maintain higher signaling rates without needing massive overvolts like many standard DDR5 kits that exceed 7000 MT/s.
You can use CUDIMMs on extant AMD 600 and 800 series platforms with Ryzen 8000 and 9000 CPUs, but only in "Bypass Mode". Bypass Mode is exactly what it sounds like—the clock drivers are bypassed, and the module is accessed just like a normal DDR5 DIMM. The biggest problem is that the XMP/EXPO drivers for CUDIMMs will be configured with normal non-Bypass operation in mind, which means you're going to have to do some manual memory tuning if you want something approaching normal performance. In our testing, DDR5 CUDIMMs on X870E run at just 3200 MT/s by default in Bypass Mode, an abysmal speed.
Intel's current-generation CPUs, the Core Ultra 200 series based on "Arrow Lake", expect CUDIMMs as default. It's likely that AMD's next-generation CPUs, based on the Zen 6 architecture, will as well. However, there's a catch—even those chips won't be able to properly support CUDIMMs on extant motherboards, at least according to 1usmus. He notes in another xweet that "the CA bus needs to be modified (basically a new chipset.)"
In other words, while AMD's next-generation CPUs will assuredly install into most Socket AM5 motherboards and work just fine, you'll be limited to using standard DDR5 DIMMs (or CUDIMMs in Bypass Mode), and that could mean leaving some performance on the table versus pairing one of the parts with a new 900-series chipset. Slow memory isn't the end of the world—especially on an X3D CPU—but it's something to keep in mind if you're planning an upgrade to Zen 6 when it comes out.
