AMDآ’s Bulldozer and Bobcat Processors Preview

AMD is starting to talk about its new Bulldozer and Bobcat processors. Today we have some notes on the new processors that will interest you as well as give you a peek under the heatspreader. Not a full blown look, but just a glimpse of what is to come, hopefully.

Introduction

Do "Bulldozer" and "Bobcat" sound familiar? Well of course those code names do! We started reporting on those over three years ago, in July of 2007 to be exact. In fact we have only written six AMD CPU based articles since then; know why? Because pretty much nothing has truly changed on the AMD product front. While that sounds a bit brutal, it is true. Here is what AMD told us in 2007.

Bulldozer is slated to be launched into the "Sandtiger" server and workstation arena in mid-to-late 2009 using DDR3 memories.

Well we all know what happened after that, nothing much. Well, Phenom and Phenom II were both failures in the high end desktop market. These Phenoms do however make for a good bargain basement CPUs though and surely AMD has been selling lots of Phenom silicon based on price...and still not making any money at it. But here we are once again with Bulldozer being promised to bring huge changes to the server and high end desktop spaces.

I am sorry if I sound a bit pessimistic. But I am. Let me just call it the way I see it. I am not going to get excited about this processor till I am holding one in my hand and have a working AM3+ socket motherboard that can fully take advantage of all the Bulldozer processor features. When I have that, I will get excited. Hopefully we will all be excited and stay that way.

Bulldozer Notes

Below you will see the full Bulldozer and Bobcat (mobile) slide deck that we were presented. I am going to add a list of information I gleaned from AMD when we were presented the slide deck. In all honesty, AMD did not have a lot to say about Bulldozer beyond the slides and the engineer I was talking to was purely dedicated to server. But with AMD, we see the server parts "slide down" into the desktop arena with minimal features removed that are generally not important to desktop any way.

Bulldozer core "modules" will consist of two 4-pipeline cores that share a Float Point Scheduler and two 128-bit FMACs. Since a very small amount (outside of HPC) is FP calculations in today's code, the shared FP scheduler allows some significant power savings. The shared dual 128-bit FMACs can be used by each core or doubled up and used as a 256-bit FMAC. For this to be beneficial however, it will have to be specifically code for.

These cores also share an L2 cache. These modules can be arranged and connected via HyperTransport Bus facilities build multi-core processors. The 6000 series server processors will have 12 to 16 cores, or 6 to 8 modules. The 4000 series will have 4 to 8 cores. Server side chipset will be identical to what is currently on the market and G34 (6000 series) and C32 (4000 series) sockets will accept these server processors. These processors will work inside the exact same thermal envelopes as the previous processors, but will of course have up to double the cores.

These will be 32nm processors produced by GlobalFoundries.

"Significant enhancements" have been made to the memory controller that will represent a substantial increase in memory throughput, but that is all that would be said on the matter.

It was interesting to hear AMD compare its Bulldozer module to current Intel HyperThreading architecture and you will see the comparison made on the slides below. AMD seemed to be of the mind, "Why do we need something akin to HyperThreading when we can add an additional core to our module for about a 5% increase in die size?" AMD kept with the 2-core module to HyperThreading comparison throughout the talk.

More low power states and more advanced and granular clock gating will also be part of Bulldozer and upcoming Northbridge parts for the desktop. Expect to see two channels of DDR3 memory per module as well. As well a new modes of AMD's TurboCore technology that "overclocks" the processors.

On the desktop side, while this was not discussed, I would expect to see 4 and 8 core Bulldozer processors at the desktop launch, whenever that may be. AMD quoted no dates and to be perfectly honest, I did not ask as I did not want more Bulldozer promises.

What Makes This Special

This is what we said back in 2007.

The statements that most needs to be focused on are, "Continued Scaling for single-thread performance," and "Partitioned for future scalability and modularity." That would tell me that Bulldozer could be morphed according to the importance of the application whether it has specific multi-thread needs or single thread needs and still take advantage of all its resources. Currently using our dual and quad core processors, when we have a resource-hungry single threaded application, which is still usually the case, our other core(s) are sitting there doing nothing. Bulldozer seems to be able to unite its core to work together on a single threaded application. As for the "partitioned" statement I would have to read into that the heart of Bulldozer is somewhat akin to AMD’s M-SPACE design methodology in that it could be very possibly for AMD to build Bulldozer cores designed for specific applications and hardware.

Now while Bulldozer design has changed a good bit since 2007, its commitment to its core function has stayed alive from what we can see at the module level in the slides. We have a shared FP and SIMD unit front end along with two out of order back ends. I might be wrong on this but our operating systems should see the Bulldozer module as a single processor core with SMT enabled. Hence the continued comparison to HyperThreading, except unlike HyperThreading where Intel is "shoehorning" in instructions, the Bulldozer module will have another "entire core" to handle those instructions. It is all still a bit murky to me but this seems to be the direction. Threaded single threaded goodness?

(Edit: We now have information from AMD that makes this clear. The approach that AMD laid out years ago has changed.)

Each integer core will be able to run one software thread, and these threads can all be done simultaneously, unlike an SMT-type technology that lets two threads share one core. You typically find SMT technology on processors with much lower core counts, and its shared nature can create bottlenecks, even resulting in negative throughput in some cases.

What I do know is that we want to get our hands on hardware and see what it is going to mean to the enthusiast. My fingers are crossed that AMD is poised to give Intel some much needed competition.

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