<b>Updated</b> CPU Cheatsheet - Seven Years of Covert CPU Operations

Duron and Athlon

I won't bother going into details of the early Athlon and Duron processors. They were great in their day, but they're getting to be rather long in the tooth. If there is a strong demand for more details on these processors, I will add them at a later point, but for now I simply recommend that you bite the bullet and upgrade.

For those interested in some historical information, here are a few more tidbits. The early Argon, Pluto and Orion Athlon chips had L2 cache chips contained within the Slot A cartridge. This cache could run at 1/2, 2/5, or 1/3 of the core clock speed - the faster the core, the lower the ratio. This led to situations where, for example, a 700 MHz Athlon with 350 MHz L2 would outperform the more expensive 750/300, or the 850/340 would beat the 900/300 due to the slower cache. Generally speaking, performance comparisons between the Athlon and Pentium III chips of the day were neck-and-neck affairs, with each side winning some benchmarks. Athlon had better x87 floating point performance, while Intel generally won out with features like MMX and SSE - at least in applications that were properly optimized.

The socket A processors switched to an integrated full-speed L2 cache, but the cache was half as large. The increased speed and reduced latencies, however, more than made up for the decrease in cache size. At this time, AMD was able to actually surpass Intel in raw performance for a period of time. The Athlon Thunderbird eventually reached 1.4 GHz, while the Pentium III tried for 1.13 GHz and failed. Later versions of the Pentium III dubbed Tualatin would eventually reach 1.4 GHz, but those only came after the introduction of the Pentium 4. Athlon during these times was the chip for gaming systems.

One other item worth noting is that all of the Athlon and Duron systems used the EV6 bus protocol acquired from DEC/Alpha. This was a double-pumped system bus, which improved performance relative to older buses like that used in P6 motherboards. The bus speeds listed in the charts are the base bus speed, which is then multiplied by the CPU multiplier to arrive at the final CPU speed. However, due to the double-pumping, many motherboards will list the bus speed as the doubled value. The actual performance increased gained from the doubling of the bandwidth is not as large as some might expect, but it probably accounts for somewhere between 5 to 15 percent of the total performance of the architecture, depending on the application.

The Athlon 64 and Opteron processors, meanwhile, have switched to a HyperTransport bus running at 800 MHz on the early chips and 1 GHz on socket 939 chips. The main benefit of the HT bus is that it doesn't require as many traces (wires), so it makes motherboard layouts somewhat easier to design. This also allows for multiple high-speed bus connections when used in SMP systems without resorting to designs with more layers.

Athlon XP and Sempron Processors

Athlon XP (Desktop) & Sempron (Desktop Value)
Athlon XP 1500+	1333	Palomino	256	133.3	10.0X
Athlon XP 1600+	1400	Palomino	256	133.3	10.5X
Athlon XP 1700+	1467	Palomino/TBA	256	133.3	11.0X
Athlon XP 1800+	1533	Palomino/TBA	256	133.3	11.5X
Sempron 2200+	1500	Thoroughbred B	256	166.7	9.0X
Athlon XP 1900+	1600	Palomino/TBA	256	133.3	12.0X
Athlon XP 2000+	1667	Palomino/TBA	256	133.3	12.5X
Athlon XP 2000+	1667	Thorton	256	133.3	12.5X
Athlon XP 2000+	1533	Barton	512	133.3	11.5X
Athlon XP 2100+	1733	Palomino/TBA	256	133.3	13.0X
Sempron 2400+	1667	Thoroughbred B	256	166.7	10.0X
Athlon XP 2200+	1800	TBA/TBB	256	133.3	13.5X
Athlon XP 2200+	1800	Thorton	256	133.3	13.5X
Sempron 2500+	1750	Thoroughbred B	256	166.7	10.5X
Athlon XP 2200+	1667	Barton	512	133.3	12.5X
Sempron 2600+	1833	Thoroughbred B	256	166.7	11.0X
Athlon XP 2400+	2000	Thoroughbred B	256	133.3	15.0X
Athlon XP 2400+	2000	Thorton	256	133.3	15.0X
Athlon XP 2400+	1800	Barton	512	133.3	13.5X
Athlon XP 2500+	1867	Barton	512	133.3	14.0X
Sempron 2800+	2000	Thoroughbred B	256	166.7	12.0X
Athlon XP 2600+	2133	Thoroughbred B	256	133.3	16.0X
Athlon XP 2500+	1833	Barton	512	166.7	11.0X
Athlon XP 2600+	2083	Thoroughbred B	256	166.7	12.5X
Athlon XP 2600+	2000	Barton	512	133.3	15.0X
Athlon XP 2600+	1917	Barton	512	166.7	11.5X
Athlon XP 2700+	2167	Thoroughbred B	256	166.7	13.0X
Athlon XP 2800+	2250	Thoroughbred B	256	166.7	13.5X
Athlon XP 2800+	2083	Barton	512	166.7	12.5X
Athlon XP 3000+	2167	Barton	512	166.7	13.0X
Athlon XP 3000+	2100	Barton	512	200	10.5X
Athlon XP 3200+	2200	Barton	512	200	11.0X
*** All system buses for Athlon XP, Sempron, Athlon 64, and Opteron are "double pumped", so their data rate is twice the bus speed. The multiplier is based off the listed speed.

Many of the processors listed in the charts were not commonly available, so they may not be well known. Some of these parts were shipped to OEMs who had special requirements, for example they might want to use cheaper PC2100 RAM with a Barton core. Some of the listed chips might also have been mobile parts which were mistakenly listed in the wrong table. However, the majority of these chips actually do exist in various PCs. Note also that some parts were likely to be seen more in overseas markets than in the US. If you are sure that a part is incorrect or doesn't exist, feel free to post a comment or send an email.

Athlon XP tweaked some of the finer details of the Athlon architecture to improve performance. Since XP was also going up against Pentium 4 instead of Pentium III, AMD (re)introduced model numbers and began their "clock speed isn't everything" campaign. According to AMD, the XP line was rated in terms of performance relative to the Thunderbird core, but few people actually believe that. It was almost surely market driven, as the Pentium 4 was scaling rapidly in clock speed, and the Athlon cores couldn't possibly keep up in raw MHz. And of course, AMD is correct that clock speed isn't everything - average instructions executed per clock (IPC) multiplied by clock speed would give you the real instruction throughput. Unfortunately, coming up with a precise measurement of IPC is virtually impossible - it varies depending on the code executed. Still, clock-for-clock, Athlons are definitely faster than P4 chips, and the PR ratings were relatively accurate, at least in the beginning.

As the "processor wars" continued, both companies released tweaked designs. Thoroughbred was a process shrink that brought higher clock speeds, but not as high as initially desired. A reworked Thoroughbred B core - which added an extra layer to the core, among other things - helped raise the clock limit a bit more and allowed Athlon XP to eventually reach 2250 MHz. Note that Thoroughbred B cores can often overclock to 2.3 to 2.4 GHz with sufficient cooling, while the A versions are often limited to ~2.1 GHz.

After Thoroughbred, AMD added more cache with the Barton core, and readjusted their model numbers accordingly, since more cache brought more performance. This was really where the model numbers started to become suspect, though, since Intel had also added more cache and increased bus speeds without "adjusting" any model numbers. The 2500+, 2600+ and 2800+ tended to struggle a bit in keeping up with their Intel counterparts, but the real problem came when Intel released the 200 MHz (800 FSB) "C" version of their Pentium 4. The jump to 3200+ with the 200 MHz FSB really only kept the Athlon XP competitive with the P4 2.8C in overall performance comparisons. Of course, here the model names were a stroke of genius, as many people simply assumed that a 3200+ really was the equivalent of the 3.2C.

Athlon XP-Mobile Processors

Athlon XP-M (Mobile)
Athlon XP-M 850	850	Palomino	256	100	8.5X
Athlon XP-M 900	900	Palomino	256	100	9.0X
Athlon XP-M 950	950	Palomino	256	100	9.5X
Athlon XP-M 1000	1000	Palomino	256	100	10.0X
Athlon XP-M 1100	1100	Palomino	256	100	11.0X
Athlon XP-M 1200	1200	Palomino	256	100	12.0X
Athlon XP-M 1400+	1200	Thoroughbred	256	133.3	9.0X
Athlon XP-M 1500+	1300	Palomino	256	100	13.0X
Athlon XP-M 1600+	1400	Palomino	256	100	14.0X
Athlon XP-M 1500+	1333	Thoroughbred	256	133.3	10.0X
Athlon XP-M 1600+	1400	Thoroughbred	256	133.3	10.5X
Athlon XP-M 1700+	1467	Thoroughbred	256	133.3	11.0X
Athlon XP-M 1800+	1533	Thoroughbred	256	133.3	11.5X
Athlon XP-M 1900+	1600	Thoroughbred	256	133.3	12.0X
Athlon XP-M 1900+	1467	Barton	512	133.3	11.0X
Athlon XP-M 2000+	1667	Thoroughbred	256	133.3	12.5X
Athlon XP-M 2000+	1533	Barton	512	133.3	11.5X
Athlon XP-M 2100+	1600	Barton	512	133.3	12.0X
Athlon XP-M 2200+	1800	Thoroughbred	256	133.3	13.5X
Athlon XP-M 2200+	1667	Barton	512	133.3	12.5X
Athlon XP-M 2400+	1800	Barton	512	133.3	13.5X
Athlon XP-M 2500+	1867	Barton	512	133.3	14.0X
Athlon XP-M 2600+	2000	Barton	512	133.3	15.0X
Athlon XP-M 2800+	2133	Barton	512	133.3	16.0X
*** All system buses for Athlon XP, Sempron, Athlon 64, and Opteron are "double pumped", so their data rate is twice the bus speed. The multiplier is based off the listed speed.

There's not really a whole lot to say about the Mobile AMD processors. They are identical to their desktop counterparts, except they run on lower voltages and can run at reduced clock speeds to save power. Later on, the Athlon XP-M processors gained tremendous popularity due to their unlocked multipliers, which allowed them to overclock very well, as you could keep the bus speed close to the standard 200 MHz.

There are some OEM parts as well in the Mobile Athlon market which use a different socket than the standard 462 pin socket A. For the Athlon XP, there is a 563 pin version, and for Athlon 64 there is a 638 pin version. Further details and information on these parts is, at present, lacking.

Athlon 64 and Opteron Processors

Athlon 64 & "Performance" Sempron
Sempron 3100+	1800	Paris*	256	200	9.0X	754
Athlon 64 2800+	1800	Clawhammer	512	200	9.0X	754
Athlon 64 2800+	1800	Newcastle	512	200	9.0X	754
Athlon 64 3000+	2000	Clawhammer	512	200	10.0X	754
Athlon 64 3000+	2000	Newcastle	512	200	10.0X	754
Athlon 64 3200+	2000	Clawhammer	1024	200	10.0X	754
Athlon 64 3200+	2200	Newcastle	512	200	11.0X	754
Athlon 64 3400+	2200	Clawhammer	1024	200	11.0X	754
Athlon 64 3400+	2400	Newcastle	512	200	12.0X	754
Athlon 64 3500+	2200	Newcastle	512	200	11.0X	939
Athlon 64 3700+	2400	Clawhammer	1024	200	12.0X	754
Athlon 64 FX-51	2200	Sledgehammer	1024	200	11.0X	940
Athlon 64 3700+	2600	Newcastle	512	200	13.0X	754
Athlon 64 3800+	2400	Newcastle	512	200	12.0X	939
Athlon 64 FX-53	2400	Sledgehammer	1024	200	12.0X	940
Athlon 64 FX-53	2400	Sledgehammer	1024	200	12.0X	939

Opteron**
Opteron x40	1400	Sledgehammer	1024	200	7.0X
Opteron x42	1600	Sledgehammer	1024	200	8.0X
Opteron x44	1800	Sledgehammer	1024	200	9.0X
Opteron x46	2000	Sledgehammer	1024	200	10.0X
Opteron x48	2200	Sledgehammer	1024	200	11.0X
Opteron x50	2400	Sledgehammer	1024	200	12.0X
* The Paris core does not support 64-bit computing. It is included with the Athlon 64 because of the socket and because the integrated memory controller puts it ahead of the Athlon XP in performance.
** All Opterons are available in 1xx, 2xx, and 8xx versions. x=1 is for single processor systems, x=2 is for up to dual processor systems, and x=8 is for up to octal processor systems.
*** All system buses for Athlon XP, Sempron, Athlon 64, and Opteron are "double pumped", so their data rate is twice the bus speed. The multiplier is based off the listed speed.

With the Athlon 64, as the name suggests AMD added support for 64-bit addresses and integers. This was done by widening their pathways and registers, but it wasn't a radical redesign of the core Athlon architecture. It has a pipeline that was increased to 12/17 stages, it got SSE2 support added, and the system bus was switched to a HyperTransport bus. The longer pipelines allow it to scale to somewhat higher clockspeeds, and the HyperTransport buses - there are three in the Opteron - allow for better SMP, but the core remains essentially the same. The addition of x86-64 support has garnered a lot of attention, but so far it's pretty much marketing hype. It has potential to improve performance once 64-bit support arrives, but that potential has not yet been realized in the mainstream market. The scientific and academic community, however, has greeted the introduction of affordable 64-bit processing with open arms. Most consumers, meanwhile, are stuck waiting for Windows XP-64.

The reason for the superior performance of the Athlon 64 - in current 32-bit code as well as in 64-bit code to a lesser extent - lies mostly with the integrated memory controller, which dramatically reduces memory latencies. In effect, it helps to turn system RAM into a very large but still relatively slow L3 cache. It also continues to reduce memory latencies as clock speeds increase. Memory latencies on the Athlon XP were roughly 81 ns at 3200+ speeds, and the P4 3.2C was around 77 ns latency. Meanwhile, the Athlon 64 3400+ comes in at an astonishingly low 48 ns. As mentioned before, those latency figures are getting somewhat close to L3 cache values - for example, the L3 cache in a 3.06 GHz Xeon is about 10 ns. It's still four times slower, but it's also twice as fast as RAM on a P4 system.

No better example of this can be found than the newly introduced Paris core, a.k.a. Sempron 3100+. At 1.8 GHz, it is substantially slower than the fastest Athlon XP in core speed, and yet in typical use it outperforms even the Athlon XP 3200+. This from a part that has half as much cache as the Barton and Newcastle cores! The only area where it fails to keep up is in tasks that generally fit within the L1/L2 cache of the CPU, i.e. certain encoding tasks. In that case, the lack of raw clockspeed is a hindrance.

Of course, reduced latency isn't the entire story of the Athlon 64. In 64-bit mode, the number of useable registers for both integer and floating point operations has been doubled. Depending on the code being run, this could potentially bring 10 to 20 percent more performance. Certain applications that make heavy use of 64-bit integers can also benefit from the added 64-bit support, for example cryptography and encoding tools. However, MMX and SSE have provided alternative means of improving 64-bit integer performance for many years now - they just require more programming effort to realize.