Date:
Tuesday , November 29, 2011
Author:
Kyle Bennett
Google +1

HardOCP Readers Ask AMD Bulldozer Questions

AMD came to HardOCP after the lackluster Bulldozer desktop launch and wanted to reach out to the hardware enthusiast community by answering questions that many of us had. We posted a HardForum thread and allowed [H] readers to ask their questions. AMD culled through the questions and AMD staffers answered 10 of the questions.

Introduction

Shortly after our AMD Bulldozer / FX-8150 Desktop Performance Review, AMD wanted to reach out to the enthusiast hardware community and answer some of the many questions that our readers had. We posted a thread in the HardForum and allowed our readers to ask AMD questions directly. You can find all of the 100 questions asked on these pages. As you might know, since then, AMD fired approximately 1,400 employees. While we expected more questions to be answered, we are understanding of the reduction of AMD employees, we are also accepting of the fact that resources to answer these questions are very much slimmed down. So what we have been presented by AMD are 10 questions that it thinks we would most like to see answered. These are those questions and answers.

10 Enthusiast Questions about Desktop Bulldozer

1. Why was the L1 cache size reduced going from Phenom II to Bulldozer?

Mike Butler, Senior Fellow Design Engineer, AMD - Over the years, AMD CPU architects have analyzed and simulated different client and server workload data footprints to efficiently size all levels of cache and have worked to optimize performance. For "Bulldozer" AMD implemented a write-thru L1D cache and focused on improving pre-fetch algorithms and increasing L1D cache bandwidth on popular small block transfers. For those less frequent, larger block transfers we rely upon the efficiencies built into our large 16-way 2MB L2.

Based on the average workloads today, we see this new design – despite the smaller L1 cache – as a more efficient way to process data.

2. Why are the integer operation benchmarks so low compared to even previous AMD 4 cores?

Mike Butler, Senior Fellow Design Engineer, AMD - "Bulldozer" is a new microarchitecture that differs in several ways from previous generations. The "Bulldozer" architecture uses both dedicated and shared resources, allowing for a more efficient design, improved instructions per watt and maintaining IPC over our widest operating range – from top boost frequencies in unlocked desktops to throughput server workloads at lower voltage, a range unmatched in prior AMD architecture generations.

As such, some individual benchmarks will show different performance levels (some higher, some lower) than prior core designs. The net performance delivered on multi-threaded applications represents a significant advancement in throughput, despite some older benchmarks not benefitting from the unique features and tradeoffs that went into the Bulldozer microarchitecture.

It is also important to note that the "Bulldozer" architecture is configured and optimized for server throughput. The two integer execution cores present in Bulldozer are designed to deliver area- and power-efficient multi-threaded throughput.

3. It seems that the idea of modules and cores sharing parts is brilliant, but the idea of increasing frequency while lowering IPC seems like a step backwards. Why was this decided on?

Mike Butler, Senior Fellow Design Engineer, AMD - Clearly, IPC is an important factor in processor performance, and IPC has decreased slightly in this first instantiation of "Bulldozer." That said there are multiple performance factors – and trade-offs – that went into the design of the forward-looking "Bulldozer" architecture.

The new CPU core delivers higher frequency while maintaining IPC, improved multi-thread (parallel computing) performance, instructions per watt, advanced boost functionality, new x86 instruction sets, and over-clock capabilities never seen in previous microarchitectures. We believe these enhancements will show positive lift for end-users as new operating systems and software applications take advantage of the new features inside "Bulldozer." And, looking forward, as process technology matures over time, the core is well structured for potential increased frequencies in the future.

4. Based on various reviews and benchmarks, the price vs performance of BD seems subpar relative to current Intel SB offerings. Can you explain you competitive positioning relative to Intel?

Adam Kozak, Product Marketing Manager, AMD - AMD designed this part around applications and environments that we believe our customers use – and which we expect them to use going forward. The architecture focuses on high-frequency and resource sharing to achieve optimal throughput and speed in next generation applications and high-resolution gaming.

This is a forward-looking, innovate approach to CPU design. And while that is difficult to measure with older, single threaded benchmarks, we believe the AMD FX CPUs offer a great experience for how our performance customers use their PCs today.