4.3 Advanced Micro Devices (AMD) Processors
Until
late 1999, Intel had the desktop
processor market largely to itself. There were competing incompatible
systems such as the Apple Mac, based on processors from Motorola,
IBM, and others, but those systems sold in relatively small numbers.
Some companies, including Cyrix, IDT, Harris, and AMD itself, made
Intel-compatible processors, but those were invariably a step behind
Intel's flagship processors. When those
companies—which Intel calls
"imitators"—were producing
enhanced 286s, Intel was already shipping the 386 in volume. When the
imitators began producing enhanced 386-compatible processors, Intel
had already begun shipping the 486, and so on. Each time Cyrix, AMD,
and the others got a step up, Intel would turn around and release the
next-generation processor. As a result, these other
companies' processors sold at low prices and were
used largely in low-end systems. No one could compete with Intel in
their core market.
All of that changed dramatically in late 1999, when AMD began
shipping a processor called the Athlon. The Athlon
didn't just match the best Intel processors. It was
faster than the best Intel could produce, and was in many respects a
more sophisticated processor. Intel had a fight on its hands, and
it's remained so to the present day.
If you ever take a moment to appreciate how much processor you can
get for so little money nowadays, give thanks to AMD. Without AMD,
we'd all still be running sixth-generation Intel
processors at 500 MHz or so. An entry-level Intel processor would
cost $200 or $250, and a high-end one (that might run at 750 MHz)
would probably cost $1,000 or more. The presence of AMD as a worthy
competitor meant that Intel could no longer play the game of
releasing faster processors in dribs and drabs at very high prices.
Instead, they had to fight for their lives by shipping faster and
faster processors at lower and lower prices. We all have AMD to thank
for that, and Intel should thank AMD as well. Although
we're sure Intel wishes AMD would just disappear
(and vice versa), the fact is that the competition has made both
Intel and AMD better companies, as well as providing the obvious
benefits to us, the users.
The following sections describe current and recent AMD processor
models.
4.3.1 The AMD Athlon Family
The AMD Athlon, which was originally codenamed the K7 and began
shipping in August 1999, was the first Intel-compatible processor
from any maker that could compete on equal footing with mainstream
Intel processors of the time. First-generation Athlon processors
matched or exceeded Katmai-core Pentium III processors in most
respects, including (for the first time ever) floating-point
performance. Intel finally had a real fight on its hands.
Although AMD represented the Athlon as the first seventh-generation
processor, we regard the K7 Athlon as essentially an enhanced
sixth-generation processor. Athlon has, in theory, several advantages
relative to the aging Intel sixth-generation architecture, including
the ability to perform 9 operations per clock cycle (versus 5 for the
Pentium III); more integer pipelines (3 versus 2); more
floating-point pipelines (3 versus 1); a much larger L1 cache (128 KB
versus 32 KB); more full x86 decoders (3 versus 1); and a faster FSB
(100 MHz double-pumped to 200 MHz by transferring data on both the
rising and falling edges of the clock cycle versus the single-pumped
Intel 100/133 MHz bus, which transfers data only once during a clock
cycle). While all that was very nice, tests showed that in practice
the K7 Athlon and Pentium III were evenly matched at lower clock
speeds, with the Pentium III sometimes showing a slight advantage in
integer performance, and the Athlon a slight advantage in
floating-point performance. At higher clock speeds, however, where
the Pentium III L2 cache running at full CPU speed comes into play,
the Coppermine Pentium III won most benchmarks handily.
AMD produced two variants of the
first-generation Athlon, both in Slot A form. The earliest Athlons
used the 0.25 K7 core, but AMD transitioned within a few
months to the improved 0.18 K75 core, which was codenamed
Pluto for speeds lower than 1 GHz and
Orion in the 1 GHz model. Although the K7 and
K75 Athlons are good processors, they have the following drawbacks:
- Poor chipset and motherboard support
-
Initial acceptance of the Athlon was hampered because the only
chipset available was the AMD-750, which was originally intended as a
technology demonstrator rather than as a production chipset. The VIA
KX133 chipset, originally planned to ship at the same time as the
Athlon, was significantly delayed, and motherboards based on the
KX133 began shipping in volume only in Q2/2000. Many motherboard
manufacturers delayed introducing Athlon motherboards, and their
first products were crude compared to the elegant motherboards
available for the Pentium III. In addition to indifferent quality,
stability, compatibility, performance, and features, first-generation
Athlon motherboards were in short supply and relatively expensive
compared to comparable models for the Pentium III. In addition,
KX133-based motherboards have problems of their own, including their
inability to support Slot A Thunderbird-core Athlons. AMD soon made
it clear that Slot A was an interim solution and that they would
quickly transition to Socket A, so manufacturers devoted little
effort to improving orphaned Slot A motherboards.
- Fractional CPU-speed L2 cache
-
Like the Deschutes-core Pentium II and the Katmai-core Pentium III,
K7 Athlons used L2 cache running at half CPU speed. Unlike the
Coppermine Pentium III, which uses on-die L2 cache running at full
CPU speed, the Athlon uses discrete L2 cache chips, which AMD must
buy from third parties. The Athlon architecture allows running L2
cache at anything from a small fraction of CPU speed to full CPU
speed. AMD has taken advantage of this as they have introduced faster
versions of the Athlon by reducing the speed of L2 cache relative to
processor speed, allowing them to use less expensive L2 cache chips.
The Athlon/700 and slower run L2 cache at 1/2 CPU speed; the
Athlon/750, /800, and /850 run L2 cache at 2/5 CPU speed. The
Athlon/900 and faster run L2 cache at 1/3 CPU speed. Unfortunately,
compared to the full-speed Pentium III Coppermine L2 cache, the slow
L2 cache used on fast Athlons decreases performance substantially in
many applications.
- High power consumption
-
Athlon processors are power-hungry, with some 0.25 models
consuming nearly 60 watts. In comparison, typical Intel processors
use one-half to one-third that amount. High power consumption and the
resulting heat production has many implications, including the
requirement for improved system cooling and larger power supplies. In
fact, for the Athlon, AMD took the unprecedented step of certifying
power supplies for use with their processor. If you build a system
around a first-generation Athlon, you must make
sure that both cooling and power supply are adequate to meet the
extraordinarily high current draw and heat dissipation of the
processor.
- Lack of SMP support
-
Until mid-2001, no multiprocessor Athlon systems existed. Although
all Athlon processors from the earliest models have been SMP-capable
(and in fact use the superior point-to-point SMP method rather than
Intel's shared bus method), dual-processor Athlon
systems had to wait for the release of the AMD 760MP chipset
(originally designated the AMD 770) in mid-2001. This early absence
of SMP support hurt Athlon acceptance in the critical corporate
markets, not so much because there was a huge demand for SMP but
because the lack of SMP support led buyers to consider the Athlon a
less advanced processor than Intel's offerings.
With the exception of SMP support, which was never lacking in the
processor, these faults were corrected in the second generation of
Athlon CPUs, which are based on the enhanced K75 core codenamed
Thunderbird. All early Athlon models used Slot
A, which is physically identical to Intel's SC242
(Slot 1), but uses EV-6 electrical signaling rather than the GTL
signaling used by Intel. Figure 4-10 shows a Slot A
Athlon processor.
Table 4-3 lists the important characteristics of
Slot A Athlon variants. Thunderbird processors were produced in very
small numbers in Slot A for OEM use and so are included in this table
for completeness, but we've never actually seen a
Slot A Thunderbird and don't know anyone who has.
Table 4-3. Slot A Athlon variants
Processor
|
Athlon
|
Athlon
|
Athlon
|
Athlon
|
Athlon
|
Athlon
|
Core
|
K7
|
K75
|
K75
|
K75
|
Thunderbird
|
Thunderbird
|
Model
|
1
|
2
|
2
|
2
|
4
|
4
|
Production dates
|
1999, 2000
|
2000
|
2000
|
2000
|
2000, 2001
|
2000, 2001
|
Clock speeds (MHz)
|
500, 550, 600, 650, 700
|
550, 600, 650, 700
|
750, 800, 850
|
900, 950, 1000
|
750, 800, 850
|
900, 950, 1000
|
L2 cache size
|
512 KB
|
512 KB
|
512 KB
|
512 KB
|
256 KB
|
256 KB
|
L2 cache speed
|
1/2 CPU
|
1/2 CPU
|
2/5 CPU
|
1/3 CPU
|
CPU
|
CPU
|
L2 cache bus width
|
64 bits
|
64 bits
|
64 bits
|
64 bits
|
64 bits
|
64 bits
|
System bus speed
|
100 MHz
|
100 MHz
|
100 MHz
|
100 MHz
|
100 MHz
|
100 MHz
|
Core voltage
|
1.6
|
1.6
|
1.6 (750) 1.7 (800/850)
|
1.8
|
1.7
|
1.75
|
I/O voltage
|
3.3
|
3.3
|
3.3
|
3.3
|
1.7
|
1.75
|
Dual CPU capable
|
|
|
|
|
|
|
Fabrication process
|
0.25
|
0.18
|
0.18
|
0.18
|
0.18
|
0.18
|
Interconnects
|
Al
|
Al
|
Al
|
Al
|
Al/Cu
|
Al/Cu
|
Die size (mm2)
|
184
|
102
|
102
|
102
|
120
|
120
|
Transistors (million)
|
22
|
22
|
22
|
22
|
37
|
37
|
Like Intel, with its shift from Slot 1 to Socket 370 for low-end
processors, AMD recognized that producing cartridge-based slotted
processors was needlessly expensive for the low end, and made it more
difficult to compete in the value segment. Also, improvements in
fabrication made it possible to embed L2 cache directly on the
processor die rather than using discrete cache chips. Accordingly,
AMD developed a socket technology, analogous to Socket 370, which
they called Socket A. AMD had never denied that Slot A was a stopgap
technology, and that Socket A was their mainstream technology of the
future. AMD rapidly phased out Slot A during 2000, and by late 2000
had fully transitioned to Socket A. AMD has to date produced five
major desktop processor variants in Socket A. From earliest to
latest, these include:
- Athlon (Thunderbird-core)
-
The Thunderbird Athlon was originally designated
Athlon Professional and targeted at the
mainstream desktop and entry-level workstation market, in direct
competition with the Intel Pentium III and Pentium 4. The first
Thunderbird processors used an 0.18 process with aluminum
interconnects, but by late 2000 AMD had transitioned to a
0.18 process with copper interconnects. During that
transition, AMD phased out Slot A Thunderbird models, and shifted
entirely to Socket A. Early Thunderbirds used the 100 MHz FSB
(double-pumped to 200 MHz), with later models also available in 133
MHz FSB variants. Figure 4-11 shows a Socket A
Athlon Thunderbird processor.
- Duron (Spitfire-core)
-
The Duron,
codenamed Spitfire and for a short time
designated Athlon Value, was targeted at the
value desktop market and was to be a Celeron-killer. With it AMD
straddled a fine line between matching Celeron clock speeds and
performance on the one hand, versus avoiding cannibalizing sales of
Athlon processors on the other. Accordingly, AMD differentiated the
Duron by limiting the clock speed of the fastest current Duron to one
step below the clock speed of the slowest current Athlon, by using a
smaller and less efficient L2 cache, and by making the Duron only in
100 MHz FSB versions (versus the 133 MHz FSB available on some Athlon
models). The Duron is a superb processor, and unquestionably offers
more bang for the buck than any other processor sold by AMD or Intel.
Although it achieved reasonable sales volumes in Europe it never
really took off in the U.S. because of the absence of high-quality
integrated Duron motherboards.
|
There was to have been another
variant of the Thunderbird-core Athlon, codenamed
Mustang and formally named Athlon
Ultra, but that processor never shipped except as samples.
Mustang was to be a Socket A part, targeted at servers and
high-performance workstations and desktops. It was to be an enhanced
version of Thunderbird, with reduced core size, lower power
consumption, and large, full-speed, on-die L2 cache, probably 2 MB or
more. Mustang was to have used a 133 MHz DDR FSB, yielding an
effective FSB of 266 MHz. It was intended to use a 0.18
process with copper interconnects from the start, and to require the
AMD 760 chipset or later. Alas, the Mustang never shipped. It would
have been a wonderful processor.
|
|
- Athlon XP (Palomino-core)
-
AMD originally intended to name the Palomino-core Athlon the
Athlon 4, for obvious reasons. In fact, the
first Palomino-core Athlons that shipped were the Mobile
Athlon 4 and the 1.0 GHz and 1.2 GHz versions of the
Athlon MP. Instead, given Microsoft's schedule for
introducing Windows XP, AMD decided their new processor might tag
along on the coattails of the new Windows version. Accordingly, AMD
finally named the Palomino-core Athlon the Athlon
XP. Various architectural changes from the Thunderbird
core, detailed below, allow the Athlon XP to achieve considerably
higher performance at a given clock speed than a comparable
Thunderbird. The Athlon XP is also the first recent AMD processor to
use a model designation unrelated to its actual clock speed. Figure 4-12 shows an AMD Athlon XP processor.
- Athlon MP (Palomino-core)
-
Even the first Athlon processors had the circuitry needed to support
dual-processor operation, but that remained a non-issue until the
introduction of the AMD 760MP chipset because no prior Athlon chipset
supported dual processors. In mid-2001, Tyan began shipping their
760MP-based Thunder motherboard, which supported dual Athlons, but it
was quite expensive and required a special power supply. In late
2001, Tyan began shipping the inexpensive Tiger MP dual Athlon board,
which used a standard power supply. Suddenly dual Athlon systems were
possible, and many enthusiasts set out to build one. AMD capitalized
on this new market by introducing Palomino-core Athlon XP processors
certified for dual-processor operation, which they named the
Athlon MP. In truth, a pair of standard Athlon
XPs or even Durons work properly in the Tyan MP boards. Many
hobbyists have successfully used them so, but the Athlon MP provides
a higher comfort level for OEMs and corporations who produce and buy
dual Athlon systems.
- Duron (Morgan-core)
-
The Morgan-core Duron is simply a refresh of the Spitfire Duron to
use the newer Palomino core. The advantages of the Morgan-core Duron
over the Spitfire-core Duron are analogous to the advantages of the
Palomino-core Athlon over the Thunderbird-core Athlon. The Morgan
core is essentially a Palomino core with a smaller and less efficient
L2 cache. As with the Spitfire, AMD carefully manages the Morgan to
prevent cannibalizing sales of the Athlon XP. The fastest current
Morgan is always at least one step slower than the slowest current
Athlon XP. In terms of absolute performance clock-for-clock, the
Morgan slightly outperforms the Coppermine-core Pentium III and the
Tualatin-core Celeron. If you're looking for the
absolute highest bang for your processor buck, a Morgan-core Duron is
the processor to choose. Figure 4-13 shows an AMD
Duron processor.
Table 4-4 lists the important characteristics of
Socket A Athlon and Duron variants. Note that some examples of the
Thunderbird Athlon/750, 800, and 850 use 1.70V rather than 1.75V, and
that some examples of the Duron/600, 650, and 700 use 1.5V rather
than 1.6V.
Table 4-4. Socket A Athlon and Duron variants
Processor
|
Athlon
|
Athlon
|
Athlon XP
|
Athlon MP
|
Duron
|
Duron
|
Core
|
Thunderbird
|
Thunderbird
|
Palomino
|
Palomino
|
Spitfire
|
Morgan
|
Model
|
4
|
4
|
6
|
6
|
3
|
7
|
Production dates
|
2000, 2001
|
2000, 2001
|
2001 -
|
2001 -
|
2000, 2001
|
2001 -
|
Clock speeds (MHz)
|
750, 800, 850, 900, 950, 1000, 1100, 1200, 1300, 1400
|
1000, 1133, 1200, 1333, 1400
|
1333, 1400, 1466, 1533, 1600
|
1000, 1200, 1333, 1400, 1533
|
600, 650, 700, 750, 800, 850, 900, 950
|
1000, 1100, 1200
|
L2 cache size
|
256 KB
|
256 KB
|
256 KB
|
256 KB
|
64 KB
|
64 KB
|
L2 cache speed
|
CPU
|
CPU
|
CPU
|
CPU
|
CPU
|
CPU
|
L2 cache bus width
|
64 bits
|
64 bits
|
64 bits
|
64 bits
|
64 bits
|
64 bits
|
System bus speed
|
100 MHz
|
133 MHz
|
133 MHz
|
133 MHz
|
100 MHz
|
100 MHz
|
Core voltage
|
1.75
|
1.75
|
1.75
|
1.75
|
1.6
|
1.6
|
I/O voltage
|
1.75
|
1.75
|
1.75
|
1.75
|
1.6
|
1.6
|
Dual CPU capable
|
|
|
|
|
|
|
Fabrication process
|
0.18
|
0.18
|
0.18
|
0.18
|
0.18
|
0.18
|
Interconnects
|
Al/Cu
|
Al/Cu
|
Cu
|
Cu
|
Cu
|
Cu
|
Die size (mm2)
|
120
|
120
|
128
|
128
|
100
|
106
|
Transistors (million)
|
37
|
37
|
37.5
|
37.5
|
25
|
25.18
|
AMD actually first shipped Palomino-core Athlon processors some
months before the Athlon/XP desktop processor in the Athlon 4 mobile
variant and the Athlon MP/1.0G and Athlon MP/1.2G variants, all of
which were designated by their actual clock speeds. Subsequent
Palomino-core Athlon processors are all designated using the
QuantiSpeed performance rating rather than their actual clock speeds.
For example, the Athlon XP/1500+, XP/1600+, XP/1700+, XP/1800+, and
XP/1900+ actually run at clock speeds of 1333, 1400, 1466, 1533, and
1600 MHz, respectively, as do the similarly badged Athlon MP
SMP-capable variants.
Although Palomino-core processors use the same 0.18
fabrication process used for Thunderbird-core processors, AMD made
several improvements in layout and architecture. Relative to the
Thunderbird-core Athlon, Palomino-core Athlons (including the Athlon
XP, the Athlon MP, and the Mobile Athlon 4) provide 3% to 7% faster
performance clock-for-clock, and include the following enhancements:
- Improved data prefetch mechanism
-
This allows the CPU, without being instructed to do so, to use
otherwise unused FSB bandwidth to prefetch data that it thinks may be
needed soon. This single feature accounts for most of the performance
improvement in the Palomino core relative to the Thunderbird, and
also increases the processor's dependence on a
high-speed FSB/memory bus. Better data prefetch most benefits
applications that require high memory bandwidth and have predictable
memory access patterns, including video editing, 3D rendering, and
database serving.
- Enhanced Translation Look-aside Buffers
-
Translation Look-aside Buffers (TLBs) cache
translated memory addresses. Translation is needed for the CPU to
access data in main memory. Caching translated addresses makes
finding data in main memory much faster. Palomino-core Athlons
include the following three enhancements to the TLBs:
- More L1 Data TLBs
-
Palomino-core Athlons increase the number of L1 Data TLBs from 32 to
40. The larger number of TLB entries increases the probability that
the needed translated address will be cached, thereby improving
performance. Even with 40 entries, though, the Palomino-core Athlon
has fewer L1 TLB entries than the Intel Pentium III or Pentium 4, and
the benefit of this small increase is minor.
- L2 TLBs use exclusive architecture
-
In Thunderbird-core Athlons, the L1 and L2 TLBs are non-exclusive,
which means that data cached in the L1 TLB is also cached in the L2
TLB. With the Palomino core, AMD uses an exclusive TLB architecture,
which means that data cached in the L1 TLB is not replicated in the
L2 TLB. The benefit of exclusive caching is that more entries can be
cached in the L2 TLB. The drawback is that using exclusive caching
results in additional latency when a necessary address is not cached
in the L2 TLB. Overall, exclusive TLB caching again results in a
minor performance increase.
- TLB entries can be speculatively reloaded
-
Speculative reloading means that if an address is not present in the
TLB, the processor can load the address into the TLB before the
instruction that requested the address has finished executing,
thereby making the cached address available without the latency
incurred by earlier Athlon cores, which could load the TLB entry only
after the requesting instruction had executed. Once again,
speculative reloading provides a minor performance improvement.
- SSE instruction set support
-
Palomino-core Athlons support the full Intel SSE instruction set,
which AMD designates 3DNow! Professional.
Earlier Athlon processors supported only a subset of SSE and so could
not set the processor flag to indicate full support. That meant that
SSE-capable software could not use SSE on AMD processors, which in
turn meant that AMD processors ran SSE-capable software much more
slowly than did Intel SSE-capable processors. Palomino-core Athlons
set the SSE flag to true, which allows software to use the full SSE
instruction set (but not the SSE2 instruction
set supported by Intel Pentium 4 processors). Also note that although
Palomino-core Athlons support the full SSE instruction set, all that
means is that they can run SSE-enabled software. It does not
necessarily mean that they run SSE-enabled software as fast as a
Pentium III or Pentium 4 processor does.
- Reduced power consumption
-
Palomino-core Athlons have an improved design that reduces power
consumption by 20% relative to Thunderbird, which reduces heat
production and allows the Palomino core to achieve higher clock
speeds than the Thunderbird core.
|
Rather oddly, Morgan-core Durons (based on the Athlon Palomino core)
actually draw more current than the older Spitfire-core Durons (based
on the Athlon Thunderbird core). In fact, Morgan-core Durons draw the
same current as Palomino-core Athlons operating at the same clock
speed, which leads us to believe that Morgan-core Durons are
literally simply Palomino-core Athlons with part of the L2 cache
disabled.
|
|
- Thermal diode
-
Palomino-core Athlons are the first AMD processors that include a
thermal diode, which is designed to prevent damage to the processor
from overheating by shutting down power to the processor if it
exceeds the allowable design temperature. Intel processors have
included a thermal diode for years. It is nearly impossible to damage
an Intel Pentium III or Pentium 4 processor by overheating, even by
so extreme a step as removing the heatsink/fan from the processor
while it is running. Pentium III systems crash when they overheat
badly, but the processor itself is protected from damage. Pentium 4
systems don't even crash, but simply keep running,
albeit at a snail's pace. The AMD thermal diode,
alas, is an inferior implementation. Although the thermal diode on an
AMD processor can shut down the CPU safely when heat builds gradually
(as with a failed CPU fan), it does not react quickly enough to
protect the processor against a catastrophic overheating event, such
as the heatsink falling off.
|
The Godzilla-size heatsink/fan units used on modern
high-speed processors cause catastrophic heatsink/fan unit failures
more often than you might think. Whereas Pentium 4 processors use a
heatsink/fan retention mechanism that clamps securely to the
motherboard, AMD processors still depend on heatsink/fan units that
clamp to the CPU socket itself, which isn't designed
to support that much weight, particularly in a vertical configuration
such as a mini-tower system. If the heatsink/fan unit comes loose, as
it may do when the system is shipped or moved, an AMD processor will
literally burn itself to a crisp within a fraction of a second of
power being applied. We're talking smoke and flames
here. This problem is one of the major causes of AMD systems arriving
DOA, but may also occur any time you move an AMD system. So, if you move an AMD system
or if you've just received a new AMD system,
always take the cover off and make sure the
heatsink/fan unit is still firmly attached
before you apply power to the system. You have
been warned.
|
|
Although the Athlon XP included some significant
technical enhancements over the Thunderbird-core Athlon, the change
that received the most attention was AMD's decision
to abandon clock speed labeling and instead designate Athlon XP
models with a Performance Rating (PR) system.
AMD K7-, K75-, and Thunderbird-core Athlon processors
were labeled with their actual clock speeds. AMD Athlon XP
(Palomino-core) processors use AMD's QuantiSpeed
designations, which are simply a revival of the hoary Performance
Rating system. Although AMD claims that these PR numbers refer to
relative performance of Palomino-core processors versus
Thunderbird-core processors, most observers believe that AMD hopes
consumers will associate Athlon XP model numbers with Pentium 4 clock
speeds. For example, although the AMD Athlon XP/1500+ processor
actually runs at 1333 MHz, we think AMD believes buyers will at least
subconsciously associate the 1500+ model number with the Pentium
4/1.5G, which does in fact run at a 1,500 MHz clock speed.
AMD has gone to great pains to conceal the actual clock speed
of Athlon MP processors from users. For example, they mandate that
the actual clock speed not appear in advertisements, and have
actually gone so far as to insist that system and motherboard makers
modify the BIOS to ensure that it reports only the model number and
not the actual clock speed. It's interesting that
AMD trumpeted their faster clock speeds until Intel overtook AMD and
left them in the dust in terms of clock speeds. Now that AMD can no
longer match Intel's clock speeds, clock speeds are
no longer important. Or so says AMD.
4.3.1.1 Other AMD Processors
In addition to the flagship Athlon
and Duron series, the following AMD processors remain available,
albeit in limited distribution:
- K6-2
-
The K6-2 was introduced in mid-1998 as AMD's
alternative to the Intel Pentium II and Celeron. K6-2 integer
performance is close to that of a Pentium II or Celeron at the same
clock speed, but floating-point performance is noticeably inferior.
The K6-2 never sold in large numbers, both because its performance
was inferior to Intel alternatives and because the K6-2 ran only in
obsolescent Socket 7 motherboards. With the shipment of the Athlon
and later the Duron, AMD de-emphasized the K6-2, allowing it to die a
slow death. Until early 2001, the K6-2 was still used in a few
entry-level PCs. As of June 2002, the K6-2 remains in limited
distribution in 500, 533, and 550 MHz versions.
- K6-III
-
The Socket 7 K6-III shipped in Q1/99 at 450 MHz, but the expected
faster versions never materialized. Although the K6-III was
officially discontinued in spring 2000, some vendors still had
limited numbers of the K6-III/400 and /450 in stock as of June 2002,
and we expect that these processors will remain available in
diminishing numbers throughout 2002. The K6-III was designed to
function in any K6-2 motherboard with only a BIOS update. It added a
256 KB on-chip L2 cache, which addressed the long-standing problem of
Socket 7 L2 cache being accessible only via the relatively slow
memory bus. The K6-III also supports an L3 cache residing on the
motherboard, which increases performance, but may introduce subtle
problems with existing chipsets. K6-III integer performance generally
matches the Celeron at the same clock speed. Floating-point
performance is improved relative to the K6-2, but still inferior to
Intel.
The
introduction of Socket A Athlon and Duron processors
sounded the death knell for the AMD K6-* line of processors. Still,
as long as they remain available, the K6-2 and K6-III processors are
reasonable choices for upgrading a late-model Super Socket 7 system,
to the extent that it makes sense to upgrade such a system at all.
Before you consider upgrading a system with a K6-series processor,
check both the AMD web site (http://www.amd.com) and the motherboard
manufacturer's web site to determine compatibility
between the processor and motherboard. In particular, determine
whether the motherboard supplies the proper voltages for the
processor and whether it requires a BIOS update to support the
processor properly.
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