Intel: No plans for a socketed Skylake with eDRAM

— 8:09 PM on September 1, 2015

You may recall that the surprise star of our recent Core i7-6700K review was the Core i7-5775C, a chip based on the prior-generation Broadwell architecture with a novel configuration.

You see, the Core i7-5775C is a socketed desktop processor, but it's derived from a mobile-focused product that incorporates 128MB of eDRAM on the package with the CPU. The eDRAM is present mainly to act as an accelerator for integrated graphics, and it's pretty effective in that role. Intel CPUs with Iris Pro graphics and eDRAM  have been used in Apple's iMac and in nifty little systems like the Brix Pro.

However, that eDRAM doesn't just act as a graphics cache. It's an L4 cache for the entire processor—a big, fast pool of on-package memory that can accelerate any task whose working data set fits into it.

The Core i7-5775C

We found in recent testing that the Core i7-5775C's extra cache makes it excellent for gaming with a discrete graphics card. In spite of a ~30W and ~500MHz handicap, the 5775C often matches or even outperforms the Skylake-based Core i7-6700K in recent games.

The natural next question, then, became: will there be a socketed Skylake desktop part with eDRAM, too? That chip could presumably offer the best of all worlds.

I asked this question at a briefing ahead of today's Skylake product introductions, and the answer is, sadly,  no. Intel has no plans to produce a socketed Skylake derivative with eDRAM for desktop systems.

The firm didn't elaborate on the reasons behind this decision when we asked, but there has been a change in leadership. Lisa Graff, who ran Intel's desktop business for the last couple of years, has left that role, and Gregory Bryant has taken over as Corporate Vice President and GM of Desktop Client Platforms. On Graff's watch, Intel produced several unconventional products for desktop systems based on user feedback, including the Devil's Canyon K-series products, the unlocked Pentium Anniversary Edition, and the socketed desktop Broadwell parts. With Graff out, we'll have to see whether Intel continues to deliver innovative desktop products like these under Bryant's leadership.

There may be some hope. A source familiar with Intel's plans told us that we may see a revival of the socketed desktop parts with eDRAM as part of next year's 14-nm Kaby Lake refresh. The same source indicated that one possible reason Intel didn't choose to produce a socketed Skylake with eDRAM could be the schedule. After all, the socketed Broadwells with eDRAM hit the market almost simultaneously with the first Skylake parts—and they are still scarce here in North America. The Broadwell desktop parts likely won't be available in healthy volumes until multiple Skylake models are, too. Qualifying a socketed CPU with eDRAM takes time, and it's possible a Skylake variant could put Intel in to the same sort of uncomfortable situation yet again. Skipping a generation and going directly to Kaby Lake might make the most sense.

The dimensions of the Skylake CPU and the 22-nm eDRAM chip may also have presented a problem. The two chips have to fit together on a common package. I don't have the exact dimensions of the two chips involved. We know that the packages for the mobile U- and H-series processors with eDRAM are both 42 mm wide. The LGA1151 package for socketed Skylake parts, by contrast, measures 37.5 mm in both directions. It's possible the eDRAM and CPU simply wouldn't fit.

Whatever happens, we're hoping Intel pays attention to these socketed desktop processors with big caches going forward. The benchmarks show that they're especially well-suited for gaming. That fact makes them infinitely more exciting for most enthusiasts than, for instance, the BCLK overclocking measures built into Skylake K-series chips that the company is now somewhat strangely touting as "for the gamers."

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