As part of today’s launch AMD released two new Kaveri based APUs as part of the FM2+ platform, the A10-7860K and the A6-7470K, as well as clarifying the way the new 125W Wraith stock cooler would be distributed at this time. What went under the radar almost was the release of a third part, the Athlon X4 845 CPU, featuring no integrated graphics but AMD’s newest architecture instead.

This makes good timing, because our review of AMD’s Carrizo, the mobile platform using the latest AMD architecture is set to go up in the next couple of days. AMD’s Excavator cores were the poignant part of AMD’s Tech Day in mid-2015, where the new Excavator architecture was discussed and especially in relation to the previous generation Steamroller cores.

The goal of Excavator, as we were told at the time, was to develop a series of big steps into improving the efficiency of the base Bulldozer microarchitecture through high density libraries, better metal stacks in production, more on-chip analysis to save power, more power planes to regulate those chances and everything in-between. We were told we wouldn’t see the Excavator core on the desktop in its desktop form because the design focused on the 15W-35W power window, rather than the 45W+ on the desktop.

Fast forward to today and there seems to be a slight reversal here. The new AMD Athlon X4 845 is a pair of Excavator modules in a desktop package, designed to slot right in where the Steamroller design through Kaveri has been sitting for a couple of years. Why the change? And why a single SKU at 65W, way off the 15W-35W range quoted as 'ideal' back at the Tech Day?

AMD Excavator Based Lineup
  A12 PRO-
Athlon X4
Platform Mobile Mobile Mobile Mobile Mobile Desktop
Modules 2 2 2 2 1 2
Threads 4 4 4 4 2 4
Core Freq. (GHz) 2.1-3.4 2.1-3.4 1.8-3.2 1.6-3.0 1.6-3.0 3.5-3.8
Compute Units 4+8 4+8 4+6 4+6 2+4 4+0
512 512 384 384 256 N/A
IGP Freq. (MHz) 800 800 800 720 800 N/A
TDP 15-35W 15-35W 15W 15W 15W 65W
2133 2133 2133 2133 1600 2133
L2 Cache 2x1MB 2x1MB 2x1MB 2x2MB 2x1MB 2x1MB

One thing that was made perfectly clear in AMD’s briefing on the new Athlon was that this is not a performance part – due to the nature of Excavator the new CPU would be purely an efficiency play, allowing customers to take advantage of the latest architecture in the desktop if they didn’t need the full-fat performance. Arguably you could already find Excavator in the desktop, through Dell’s Inspiron 3656 range which uses a mobile part in a desktop case with a discrete graphics card.

With the new Athlon, the fact that there is no graphics part to the FM2+ processor does raise several questions. Is this a new die specifically for the Excavator on desktop, which might run into the tens of millions of dollars to produce, or is it repurposed mobile silicon put into a desktop package. Instinct tells us it’s the latter, perhaps better binned parts to show that the core can do 3.8 GHz at 65W, but at the expense of the integrated graphics, or due to production issues the integrated graphics on die are unusable.  One of the interesting things is also the L2 cache situation, because the Excavator modules in Carrizo were designed with 1MB of L2 per module, rather than the 2MB of L2 cache per module in desktop Kaveri. This is somewhat balanced by the larger L1 data cache in Excavator, but because there is no L3 cache either, it has to rely on other Excavator enhancements (better prefetch, wider prefetch windows) in order to bring it up to speed.

The PCIe 3.0 lanes are also at x8, which is another mobile limitation rather than the result of the PCIe root complex being half-disabled.

AMD has already stated that the next generation of AMD APUs will be on the AM4 platform, code named Bristol Ridge and Summit Ridge. We assume Bristol Ridge to be Excavator based, because there has to be something between now and Zen, but it would seem to suggest that the Excavator memory controller has support for DDR3 and DDR4, similar to what was suggested when AMD announced their DDR4-capable R-series APUs for embedded late last year. This may mean that AM4 supports both DDR3 and DDR4 as a result, which would not be unsurprising given how most DRAM transitions go.

We have asked for samples when they start to circulate. The Athlon X4 845 will have a MSRP of $70.

Source: AMD

Additional, 3rd Feb: We have been told by AMD that 'The Athlon X4 845 is based on the "Carrizo" die with the GPU and FCH disabled. [T]he Athlon X4 845 supports DDR3 memory at speeds up to 2133MHz.'. Also, despite the focus on efficiency, the X4 845 will not have a configurable TDP.

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  • Gigaplex - Tuesday, February 2, 2016 - link

    Which probably means something like 80W TDP, rounded down to 65W. You still need a better cooling solution than 65W.
  • seanr - Tuesday, February 2, 2016 - link

    The 95w cooler should help keep cpu throttling down. Pretty good for a stock cooler as AMD does really seem to care about end user experience. Options and perks need to be more appreciated. It's nice to see corporations care about end users.
  • MrCommunistGen - Tuesday, February 2, 2016 - link

    I think it's interesting that they're using their 95W TDP cooler on these newer 65W TDP chips. I wonder if they could also be taking a page out of the Fiji playbook, where keeping temps lower also reduces leakage and helps keep the chips in that lower TDP range.
  • Oxford Guy - Tuesday, February 2, 2016 - link

    Part of that could be to deal with substandard motherboards that don't even put heatsinks on their three or four phase analog VRMs.
  • DrMrLordX - Tuesday, February 2, 2016 - link

    As mentioned by other posters, this is an Athlon part, which means it is a harvested die (as has been the case since at least Kaveri). It is a standard Carrizo with the iGPU disabled. FM2+ does not have the power planes required to handle Carrizo, though it certainly can do it when not supplying any power to the iGPU.

    So, to address Dr. Cutress' speculation: this product does not rely on its own separate die.
  • 0ldman79 - Wednesday, February 3, 2016 - link

    It just makes too much sense to have AM3+ available that can handle high powered chips...

    Maybe their just in such a financial bind they're having to cut back to keep the business afloat, but at this point they've handed the performance title over to Intel. It's not that the APU are bad, but the fact my FX 6300, released in 2012, is still very, very close to the fastest CPU AMD has sold is kinda sad.
  • MrCommunistGen - Wednesday, February 3, 2016 - link

    FM2+ not having the appropriate power planes to drive the Carrizo iGPU was my theory as well but on my part it was really just unfounded speculation. Is there any document you used that helped you come to that conclusion?
  • 0ldman79 - Tuesday, February 2, 2016 - link

    Let me preface this by saying 90% of my computers are AMD based...


    The fastest CPU made by AMD is how many years old? I've got an FX6300, which I do enjoy, however, AMD doesn't really have anything that is dramatically faster than my 2+ year old CPU.
  • abufrejoval - Wednesday, February 3, 2016 - link

    AMD seems very, very intent at not wasting a single cent or missing out on even the smallest opportunity to make an extra buck.

    I'm wondering if these chips aren't actually round wafer vs. rectangular die victims rather than just ordinary defects.

    I mean, every time you see people showing wafers around, you have all these incomplete chips at the edges, which prove all these etching and deposition processes are truly parallel and that leaving *out* these partial chips would be more expensive than producing unusable fragments...

    ...except that *some* of these usable fragments actually contain a fully functioning CPU (perhaps one on every wafer), with the CPU actually taking up less than 50% of the chip's area.

    So if perhaps one out of every 100 dies on a wafer is a "headless" CPU, all it takes is properly fusing off the GPU connects to produce a chip that can be used with an dGPU.

    Except, that today's mobile designs no longer really support iGPU-less operation even if they have a "turbo charged" dGPU (quotes, because it sometimes turns out that these dGPUs actually aren't faster any more).

    So they just overclock the headless mobile CPU and they have a Desktop class performance part pretty much for free.
  • Pissedoffyouth - Thursday, February 4, 2016 - link

    a 125w Athlon version of this clocked at something like 4.5ghz would be pretty cool upgrade

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