AMD K6 2 and K6 III processors
for the M571
This page contains additional information regarding AMD K6 2 and K6 3 processors.
Which Processor to use?
The most suitable upgrade processors for M571 3.2, 3.2a, and 7.0 boards are AMD K6 2 and AMD K6 3 chips. Other chips may provide some performance increase, but AMD chips discussed here offer maximum performance on M571 boards.
AMD K6 3
processors include an on-board 256KB 4 way Level 2 cache running at full
processor speed. This feature enabled the K6 3 to be marketed against Intel's
Pentium II line of processors, which had double this amount of on-board cache
running at only 1/2 processor speed. When a K6 3 is installed on an M571, the
512KB mainboard cache normally used as Level 2 cache functions as a Level 3
cache, and adds an additional 5% performance increase in some applications. The
K6 3 was available in 400 and 450 MHz models, each with two core voltage
ratings. The K6 3 incorporated the equivalent of 21.3 million transistors in
its design and is the most powerful processor to be successfully adapted to
M571 3.2, 3.2a, and 7.0 boards.
AMD K6 3
chips were introduced in February 1999 and discontinued a little over a year
later.
AMD K6 2
processors may be described as K6 3s without on-board Level 2 cache. Although
their design, incorporating the equivalent of 9.3 million transistors, is not
as sophisticated as their more powerful cousins, they are still readily
available on the market and represent the 2nd most powerful and sophisticated
processor that has been successfully adapted for use on M571 3.2, 3.2a, and 7.0
boards.
Later, AMD
introduced the K6 2+ and K6 3+ series of processors, which were primarily
intended for use in laptop computers. The thinner .018 die reduced both the
voltage and power requirements, and lowered the amount of heat these processors
produced. The K6 3+ retained the 256KB of L2 on chip cache, but the K6 2+
received a 128 KB on chip L2 cache. On chip cache meant that the laptop
manufacturers didn’t need to include L2 cache on their laptop system boards.
K6 2+
and K6 3+ processors will remain unusable until a new BIOS revision is
available for the M571 systems!
An
interesting tabulation of information that is useful for identifying and comparing
Socket 7 processors (among others) may be found at: http://users.erols.com/chare/586.htm
The
application wcpuid is one of many that are handy for identifying processors.
wcpuid can be obtained from tweakfiles.com at: http://www.tweakfiles.com/processor/wcpuid.html
What is the best chip to use in
an M571 System?
This depends on what you are using your M571 for, what you want to spend, and what is available in your area.
For an
inexpensive upgrade that produces excellent results, a K6 2 is an excellent
choice. At the time of this writing, 400 MHz and lower speeds can be found on
Ebay for less than $10 USD, including shipping. (Remember, if you are shopping on Ebay to pay close
attention to the shipping charges. It is common for these to run between $8 and
$10 above the cost of the processor!) Even a 300 MHz K6 2 will often overclock nicely; I’ve got
one running now that has been overclocked to 400 MHz, and it has been running
fine for over a year, continuously. If you plan to try and overclock your M571
system, as detailed on the Upgrade
Page, you may want to find a faster K6 2. 500 MHz and 533 MHZ processors
are common, and even these often go for less than $15 USD, shipping included.
If you want
the added performance of the K6 3, the lowest powered 333 MHz processor can
sometimes be found for less than $10 USD, shipping included. Like the K6 2, a
333 MHZ K6 3 will often overclock up to 400 MHz, with a small amount of extra
voltage as detailed on the Upgrade
Page.
380 MHz K6
3 processors are often available for around $25 USD, and these very commonly
overclock to 400 MHz with no problems.
Always
remember that the lower voltage processors, such as the 2.2 volt ones, will
generally tolerate overclocking better than the higher, 2.4 volt processors.
I was able
to get my 2.2 volt K6 3 400 to overclock to 458 MHz (83.3 x 5.5), but it would
not go faster than that. I would suggest that, if you want to try and get your
system to run at 500 MHz with a K6 3, you search for a 2.2 volt version of a
450 MHz processor, and keep your fingers crossed. These are the most desirable
processors, and are usually priced accordingly.
Can an M571 supply enough power
to a new chip?
Yes, but attention must be paid to how each installation is performed. I have seen two types of MOSFET "choppers" in the Vcore power supply: one is from Phillips, and the other is made by CET. (You can find links to these companies and download links to MOSFET data sheets on the Links Page. Details of the Vcore power circuit are available on Franc Zabkar's powernotes page; (click here). These data sheets show that the "chopper" has a power handling capacity of 86 watts for the Phillips unit and 50 watts for the CET unit at 25*C (or, 77*F) which is room temperature. Recall that CPUs are usually rated between 60*C and 70*C (or, 140*F to 158*F). In order to obtain the rated level of power handling, the inside of the computer case must be at room temperature!
Of course,
with ribbon cables blocking airflow and perhaps poor case ventilation, case
temperatures may rise far above room tempurature.
One of the
most power hungry processors used on the M571 when it was new was the AMD K6 233.
These processors had a maximum power consumption rating of 28.3 watts @ 3.2
volts (Vcore). Some Cyrix CPUs also consumed nearly this much power. It can be
seen that this level of power consumption is well under the maximum power
handling capability of either "chopper" MOSFET at 25*C. Now, with
these power levels in mind, let's look at the selection of AMD chips that can
be used on M571 3.2, 3.2a, and 7.0.
How do I achieve a 6x multiplier
setting on AMD K6 2 and AMED K6 3 processors?
The highest multiplier documented on M571 boards is 5.5x. However, a clock multiplier setting of 2x is interpreted by K6 2 and K6 3 chips as 6x. For example, a Front Side Bus setting of 66 MHz and a multiplier setting of 2x would provide a processor speed of 400 MHz (6 x 66 MHz = 400 MHz). Similarly, a Front Side Bus speed of 83 MHz and a multiplier setting of 2x would result in a processor speed of 500 MHz (6 x 83 MHz = 500 MHz).
What K6 3 processor is suitable
for my M571?
K6 3 processors were made available in two speeds, 400 MHz and 450 MHz, and two core voltages, 2.2 volts and 2.4 volts.
The
following table describes the AMD K6 3 product line:
|
Designation |
Processor
speed |
Core
voltage |
Power
dissipation |
|
AMD-K6-III/450AFX |
450 MHz |
2.2 v +/- .1 |
20.20 W |
|
AMD-K6-III/450AHX |
450 MHz |
2.4 v +/- .1 |
29.50 W |
|
AMD-K6-III/400AFR |
400 MHz |
2.2 v +/- .1 |
18.10 W |
|
AMD-K6-III/400AHX |
400 MHz |
2.4 v +/- .1 |
26.80 W |
K6 3 processors
were also made in a mobile version for laptop computers. The following table
describes the AMD K6 3 mobile product line:
|
Designation |
Processor
speed |
Core
voltage |
Power
dissipation |
|
AMD-K6-III/450ACK |
450 MHz |
2.0 v +/- .1 |
16.00 W |
|
AMD-K6-III/433ACK |
433 MHz |
2.0 v +/- .1 |
16.00 W |
|
AMD-K6-III/400ACK |
400 MHz |
2.0 v +/- .1 |
16.00 W |
|
AMD-K6-III/380AFK |
380 MHz |
2.2 v +/- .1 |
16.00 W |
Three
models of K6 3 processors are not described in any AMD technical documents, but
are commonly found. These processors work well in M571 systems:
|
Designation |
Processor
speed |
Core
voltage |
Power
dissipation |
|
AMD-K6-III/366AFK |
366 MHz |
2.2 v +/- .1 |
|
|
AMD-K6-III/350AFK |
350 MHz |
2.2 v +/- .1 |
|
|
AMD-K6-III/333AFR |
333 MHz |
2.2 v +/- .1 |
|
The 366
MHz version has a 66 MHz rated Front Side Bus rating, so one should approach
the use of faster Front Side Bus settings carefully. The 350 MHz processor has
a 100 MHz Front Side Bus rating, and the 333 MHz processor has a 95 MHz Front
Side Bus rating. Both of these processors should support any speed that is
obtainable on the M571 using 66, 75, or 83.3 Front Side Bus settings.
What K6 2 models are suitable
for my M571?
The K6 2 can also provide a useful
upgrade for M571 boards. K6 2 processors range in speed from 266 MHz to 550
MHz. The following table presents a list of K6 2 processors of 350 MHz and
above that may be used to upgrade M571 boards:
|
Designation |
Processor
speed |
Core
voltage |
Power
dissipation |
|
AMD-K6-2/550AGR |
550 MHz |
2.3 v +/- .1 |
25.00 W |
|
AMD-K6-2/533AFX |
533 MHz |
2.2 v +/- .1 |
20.75 W |
|
AMD-K6-2/500AFX |
500 MHz |
2.2 v +/- .1 |
20.75 W |
|
AMD-K6-2/475AFX |
475 MHz |
2.2 v +/- .1 |
19.80 W |
|
AMD-K6-2/475AHX |
475 MHz |
2.4 v +/- .1 |
29.60 W |
|
AMD-K6-2/450AFX |
450 MHz |
2.2 v +/- .1 |
18.80 W |
|
AMD-K6-2/450AHX |
450 MHz |
2.4 v +/- .1 |
28.40 W |
|
AMD-K6-2/400AFR |
400 MHz |
2.2 v +/- .1 |
16.90 W |
|
AMD-K6-2/400AFQ |
400 MHz |
2.2 v +/- .1 |
22.70 W |
|
AMD-K6-2/380AFR |
380 MHz |
2.2 v +/- .1 |
21.60 W |
|
AMD-K6-2/366AFR |
366 MHz |
2.2 v +/- .1 |
20.80 W |
|
AMD-K6-2/350AFR |
350 MHz |
2.2 v +/- .1 |
19.95 W |
K6 2
processors are also made in a mobile version for laptop computers. The
following table describes the AMD K6 2 mobile product line:
|
Designation |
Processor
speed |
Core
voltage |
Power
dissipation |
|
AMD-K6-2/500ADK |
500 MHz |
2.1 v +/- .1 |
20.00 W |
|
AMD-K6-2/475ACK |
475 MHz |
2.0 v +/- .1 |
16.00 W |
|
AMD-K6-2/450ADK |
450 MHz |
2.1 v +/- .1 |
16.00 W |
|
AMD-K6-2/433ADK |
433 MHz |
2.1 v +/- .1 |
16.00 W |
|
AMD-K6-2/400ACK |
400 MHz |
2.0 v +/- .1 |
16.00 W |
|
AMD-K6-2/400AFK |
400 MHz |
2.2 v +/- .1 |
16.00 W |
|
AMD-K6-2/380AFK |
380 MHz |
2.2 v +/- .1 |
16.00 W |
|
AMD-K6-2/366AFK |
366 MHz |
2.2 v +/- .1 |
16.00 W |
|
AMD-K6-2/350AFK |
350 MHz |
2.2 v +/- .1 |
16.00 W |
These
chips can be found at dealers and at the sources listed for the K6 3. My latest
checks indicate that $30 to $40 USD is a reasonable price range for a K5 2 500
MHz chip.
Why are power dissipation
figures included?
2.4 core volt chips put out more heat than other chips. The top power consumers in this list are the K6 3 450, K6 3 400, K6 2 475 and K6 2 450 chips with 2.4v Vcore ratings. All of these chips consume about the same amount of power as the old K6 233. No matter what chip is used, install a high capacity processor cooling fan with thermal grease. The lowest rated processors specify a 60* C operating environment, which is 140* F. 60*C is quickly reached in a small, poorly vented cases where a number of expansion cards add heat and ribbon cables block air flow.Take steps to keep case temperature at a moderate level! The last letter in AMD's chip designation indicates environmental temperature. Refer to AMD documentation for additional information. When planning your installation and considering the Vcore power supply capacity, keep in mind that these operating temperature ratings are well above the room temperature rating of either MOSFET chopper in the Vcore supply circuit. Keep your case cool!
Facilitating
air flow through the system case is necessary to keep temperatures low. Air
must be able to enter and leave the case, and this flow is commonly assisted by
using cooling fans. Avoid anything in the case which can block airflow. Ribbon
cables are often big offenders, but this problem can be solved by rolling up
long ribbon cable runs and securing the resulting bundle with small tie wraps.
AMD has
provided a concise guide to case layout that can be downloaded from their site:
(cooling_guide.pdf).
While this document is intended for ATX style motherboards, it provides
concepts to consider when laying out a system in a mid-tower case. Generally,
fans are more efficient when they discharge into free air, rather than blowing
into a higher realtive pressure. Another useful site for cooling is 7Volts, a collection of many useful tips and
trick for your system.
Are technical details of K6 2
and K6 3 processors available?
AMD has detailed technical specifications available on their web site. These documents are viewable and downloadable as Adobe Acrobat (.pdf) files. Click on these links to view or download information on K6 2 and K6 3 processors:
Technical
specifications on AMD K6 3 processors: http://www.amd.com/K6/k6docs/pdf/21918.pdf
Technical
specifications on AMD K6 3 mobile processors: http://www.amd.com/K6/k6docs/pdf/22655.pdf
Technical
specifications on AMD K6 2 processors: http://www.amd.com/K6/k6docs/pdf/21850.pdf
Technical
specifications on AMD K6 2 mobile processors: http://www.amd.com/K6/k6docs/pdf/21896.pdf
What is the "CXT
Core"?
AMD introduced the "CXT core" technology in K6 2 chips in November, 1998. (All K6 3 chips have CXT cores.) All K6 3 or K6 2 chips of 366 MHz or above are CXT based. K6 2 266 MHz versions did not come with the CXT core. 300, 333, and 350 K6 2s came in both non-CXT and CXT versions. Here's how to tell CXT core from non-CXT core CPUs:
26351 = CXT core (called
"Sharptooth")
26050
= non-CXT core (called "Chomper")
(Note the small 5 digit numbers in the lower left hand corner of the chip.)
CXT chips support write
allocation and write combining capabilities, which increase performance about
2% to 4% over non-CXT chips, depending on the application that is being run.
Freeware applications are available to enable write allocation and write
combining, but if you are using the 04-21-99 BIOS release, these features are
already enabled on your M571.
What about AMD K6 2+ and K6 3+
chips?
K6 2/3+ processors are not
compatible with M571 3.2, 3.2a, or 7.0 BIOS including the 4/21/99 release. Work
is underway to make a BIOS revision available that will allow the M571 to use
K6 2+ and K3 3+ chips. I am presently testing a revised BIOS that permits the
“+” series of chips to work on the M571. I have installed it on an M571 3.2a
board and, using Franc Zabkar’s information that is available on this site (M571 v7.0 Vcore - Part 3 – the voltage worked out to
1.999 volts with the 47 Kohm resistor), have the system running quite nicely. Below is a picture of
the K6 2+ 533 ACZ processor that I obtained from an Ebay auction:
The K6 2/3+
is a very desirable chip, because it is made with a thinner die than the older
line of K6 2/3s (.018 instead of .025), so they consume less power and produce
less heat. The K6 2+ has an on-die L2 cache of 128 KB, or one half of the
normal K6 3/3+ L2 cache. These chips overclock much better than the .025 die
chips: While 50 to 75 MHz increases are about all one can expect out of a K6 3,
there are K6 3+ chips running above 700 MHz! (Special cooling and voltage
considerations are needed for this!)
this page was last modified 1
August 2005