Former AMD engineer commented on bulldozers: the design was wrong

The AMD FX series processor has eight cores and 3.6GHz high frequencies, but the actual performance is unsatisfactory. Can it be attributed to the inadequacy of the new architecture? Cliff A, an engineer who had left AMD many years ago. Maier stood up and commented that this was in fact blamed on AMD's design method adopted on bulldozers. It was wrong. It was no longer hand-built, carefully tuned, and relied too much on automatic design software. Although the result was faster (relatively speaking), Unable to provide maximum performance and efficiency.

Cliff A. Maier posted on the Internet and said: "From the design map, the bulldozer is a very beautiful chip ... (but) The management team decided that cross-engineering should be done, which means that we have to give up building our hand. The design of the processor, and the shift to SoC design, results in a lot of performance, chip area, and efficiency.The reason that DEC Alphas is so fast is that each transistor is designed by hand.Intel, AMD are at least on the chip. It was always the key part of the game. Everything changed before I left. They began to rely on synthesis tools, auto-layout, and routing tools."

The old engineer exposed that: "I have long been responsible for the management of the design process before I left the service, and I have tested these tools. I let companies that sell such design tools use them for experimentation, without any time constraints, and the end result is My design is always 20% larger than our manual design, 20% slower, and there are also a series of issues such as electronic migration. This is how AMD designs the chip now, and I believe it will perform well.”

Cliff A. Maier continued to comment: "At least one thing is for sure. AMD should learn from the K8 and K8 team's successful experience and design concept, instead of using a bunch of people who have never done anything to do a project, but ultimately it will Cancellation: It took Intel many years to come up with Nehalem, AMD is still a long way off, and there is not so much money in cocoa in their banks, otherwise they will not easily compromise with Intel on antitrust issues, and they will not sell their factories. ”

It is not known whether AMD used the automatic tools to design the entire bulldozer chip, but it seems that at least some of the inefficient parts are. According to data provided by AMD, the bulldozer chip contains up to 2 billion transistors, which is more than twice as much as its own previous generation of six cores and Intel Sandy Bridge. The entire chip area is 315 square millimeters, and it must be said that the scale is huge.

Subdivided, each dual-core module of the bulldozer plus 2MB of L2 cache uses 213 million transistors, an area of ​​30.9 square millimeters, and four modules of eight cores are 852 million transistors and 123.6 square millimeters. The specific number of transistors in the 8MB L3 cache (6bpc) is not disclosed and is estimated to be approximately 405 million. This left about 750 million transistors used in the HT bus, I / O input and output, memory controller modules and other complicated internal logic and routing, the chip area occupied is not small, the efficiency is obviously too low.

Although it cannot be confirmed, it can be surmised that automatic design tools will burden the bulldozer with as many as hundreds of millions of transistors. The consequences are self-evident.

Incidentally, the Intel Sandy Bridge has a maximum of 995 million transistors, a core area of ​​258 square millimeters, and a maximum price of 317 US dollars, while the bulldozer only sells at most 245 US dollars, and the profit gap during the period will not have to mention.

In the end, I need to remind everyone that the above statement is just a statement of one person. It does not reflect all the actual situations, and some readers responded that Intel actually switched to automatic design for the most part, and some people even called it Cliff A. What Maier mentioned was just a few years ago, so everyone looked at it and it was not too true.