A version of the Athlon processor from AMD. It is the codename of the successor to the Athlon core that was codenamed K75. What is so special about this newest processor? AMD has finally moved the L2 cache on-die with the rest of the processor. This speeds up the cache significantly as it will now be running at clock speed. Also because of this change the processor will no longer need to have a processor card. Other than a few OEM version of the chip it will be produced for a socket rather than a slot (Slot-A to be precise). With these chips we see the advent of the Socket-A interface.

Right from the get-go AMD released these bad boys with speeds ranging from 750MHz to 1GHz.

Officially called the "AMD Athlonprocessor featuring performance-enhancing on-chip L2 cache memory", the "T-Bird" (easier to say) is the successor to AMD's wildly successful Athlon (now known as the "Athlon Classic". See how the tech industry moves? It took 40 or 50 years for "Citizen Kane" to become a classic, CPU's now do it in a year or less).

The T-Bird is differentiated from the Classic in a few ways:

  • On-die 256KB L2 full-speed cache. The Classic, in comparison, had 512KB of off-die (on a different chip ("die") than the CPU core) cache running at either 1/2 or 3/5 clock speed. While half the size, the on-die nature (and subsequently, the higher speed) of the T-Bird's cache significantly improves processor performance because of the lower latency (45% lower, according to AMD).
  • 0.18-micron core, vs. the 0.25 micron core of the classic. This results in higher potential clock speeds at lower power consumption and lower heat output (all things being equal). It also shrinks the die size which translates to less-expensive chips (more yield per wafer).
  • The CPU packaging changed to the "Socket-A" form factor, from the Classic's "Slot-A". The classic used a "slot" form factor because the Classic required two separate chips to function: The core itself, and the 512KB of cache. The slot form factor allows the two chips to be mounted essentially on a circuit board, with interconnections between them. Moving to the socket form factor is possible with the T-Bird because it integrated both the core and L2 on one die. A socket design is cheaper to produce, and is frankly better packaging (IMHO). (It should be noted that the T-Bird was released in a Slot-A configuration for limited OEM distribution). And the real benefit WRT performance is that the on-die cache can be accessed at the native (full) CPU clock speed, while accessing the off-die cache was slower (1/2 or 3/5 CPU clock speed).
  • The T-Bird now sports 37M transistors, up from the Classic's 22M (neither count personally verified). The additional transistors on the T-Bird are primarily due to the on-die cache.
  • Not only is the L2 cache faster on the T-Bird, but it's implemented as 16-way set associative vs. the Classic's 2-way set associative implementation. While it isn't always true that "more is better," in the case of the T-Bird vs. the Classic, 16-way is better because it has a higher likelihood of containing the data needed by the CPU. This is what cache is for, after all.
  • The T-Bird moved (in certain cases) to copper-interconnects instead of the aluminum-interconnects of the Classic. Copper is a better conductor than aluminum, but in practice it really makes no difference. The purpose for AMD's move to copper is for future, higher-speed processors that will benefit from using copper.
  • The T-Bird supports a 200MHz Front-Side-Bus (FSB) as well as the new & speedier 266MHz (FSB). The Classic supports only the 200MHz FSB. FSB speed is important because this bus connects the CPU to the "outside world" of I/O and memory, and speeding it up results in improved access speeds to them (ergo, PC133 memory).
  • And last, the focus of marketing hype is clock-speed, and the T-Bird wins in this area with the fastest chip maxing out at 1.4GHz while the Classic hits 1.0GHz (and when it did it capped the crown from Intel by becoming the first commercial CPU to reach that mark).

Of course, this is becoming moot with the release of the "Athlon XP" series which could conceivably brand the T-Bird as the "Classic 2" in the Athlon line.

"AMD Thunderbird" is a sticker often seen on generic street-market CPU fans. These fans are generally seen on unmarked crappy-looking heatsinks hailing from parts unknown, probably from some small startup Taiwanese company (or maybe from a really big one that's learned never to use its name for anything, lest it acquire a reputation like ECS). The stickers look just like AMD Athlon and AMD Duron stickers, but they're fake while lots of people like to refer to their CPU by core name, companies don't. Do you see Intel calling their Pentium 4s "Intel Northwoods" and "Intel Prescotts"? If you see this sticker on a fan or heatsink, you can be pretty sure it's not actually officially supported by AMD. Probably bad, too.

On a related note, a friend of mine once decided to stick one of these mystery coolers with the AMD Thunderbird sticker on his 1.33GHz Thunderbird-- against my advice, I might add, since bad coolers will cause the Thunderbird to (in purely technical terms) explode, and there's really no way of telling how well these coolers work unless someone's already tested it. The cooler didn't look very good either: bent fins, odd design, mystery fan. It may have been copper, but copper doesn't save a bad design. He stuck a better fan on it, we booted the computer up (also against my advice), and he started a system benchmark to see how hot it ran under full load. About forty-four degrees Celsius. Better than his old (and considerably louder) ThermalTake heatsink.

Despite this positive experience with an Asian Mystery Cooler™, I wouldn't recommend putting anything with an "AMD Thunderbird" sticker on an actual AMD Thunderbird. I may have been wrong in this case, but when it comes to things that may cause your CPU to become a little puddle of silicon and ceramic substrate, it's never a bad idea to judge a book by its cover.

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