Autor: john_at_coaxline.com
Data: Fri 26 Dec 1997 - 12:30:32 MET
Important News for Overclockers
===============================
Quite a lot of time has passed since my last update of
the
Overclocking Guide and now some really important
things
happened, which urged me to write something about this
topic.
Although I never included it in my Overclocking Guide,
the
Pentium II is a wonderful CPU to overclock. All PII
266 CPUs that I
came across worked just fine at 300 MHz and as long as
you
cooled the chip well enough, they even run at 337.5
MHZ, (4.5x75
MHz).
A simular thing used to be true for the Pentium MMX
CPUs, even
Pentium MMX 166 CPUs ran just fine at even 233 MHz
after
simply changing the multiplier.
The Time Has Changed
=======================
For a several weeks now it looks as if Intel has an
excellent yield
in the production of the Pentium MMX as well as of the
Pentium II.
This means that probably 90% of the produced chips are
of top
range spec, meaning that Intel almost only produces
Pentium
MMX 233 and Pentium II 300 CPUs. However, since a lot
of
people are still asking for Pentium MMX 166 and 200
CPUs as
well as PII 233 and 266 parts, Intel has to mark a lot
of faster parts
slower than they are in reality. Now here the
overclocking issue
comes in. Intel is aware of the fact that people know
about
overclocking and they want to get top money for top
performance.
I never thought of having a reason to buy a PII 300,
because the
PII 266 was just as good. Lots of you advised friends
to buy a
Pentium MMX 166 instead of a 233, because it ran the
same and
indeed it was. Intel doesn't want this, as everyone
can imagine.
Hence they did something that they've done once before
in the
past. I'm sure that lots of you still remember the
Pentium 133
SY022 CPUs, which wouldn't recognize any multiplier
setting
higher than x2. Intel disabled the higher multipliers
by just not
bonding one of the multiplier pins. That is the same
they are doing
now. Please understand that this is some kind of
touchy thing
when chip production starts. You can only test a CPU
after it's
packaged, which means after bonding. As long as you
are not
producing many fast chips like e.g. a Pentium MMX 233,
you are
taking the risk of wasting some high end parts by
bonding them to
only 166 or 200 MHz versions. That's why Intel never
has this
'overclock protection' in newly released chips.
However, when the
yield of high end chips is really high, even higher
than what the
market wants, you can afford castrating fast parts to
slow ones by
just bonding it.
The result of this is that Pentium MMX 166, Pentium
MMX
200, Pentium II 233 and Pentium II 266 CPUs cannot be
overclocked via higher multiplier settings anymore.
This
seems to be the case for the last 4 to 6 weeks, which
means that
there are hardly any 'overclockable' Intel CPUs on any
of the shop
shelves anymore. Only a shop that's hardly selling any
and that's
got a CPU lying around for a long time might have one
of the
'gems' left.
This restriction of the multiplier settings does of
course not affect
the overclocking via higher bus speeds. You can still
run a PII 266
at 300 MHz, but it'll have to be 75 MHz x 4, because
66 MHz x 4.5
won't work anymore. You can even push it to 333 MHz,
but this
means using 83 MHz bus speed, which runs only in very
few
boards with very few RAM types and hardly ever with
AGP
graphic cards. Forget about 100 MHz in 440FX or 440 LX
boards. I've tried it with the extremely stable LX6
from Abit and
with the best memory I could get. 83 MHz is fine in
the LX6, but
forget the 100 MHz it offers. The same is valid for
the latest
versions of the Asus LX boards that also offer you 100
MHz bus
speed - it just doesn't work. 75 MHz are fine with
Pentium II CPUs,
83 and more should rather be left alone, because the
system gets
too unstable and AGP graphic cards don't like an AGP
bus
running at 83 MHz instead of 66. 100 Mhz should be
left to the
upcoming 440BX boards and the 'Deschutes' Pentium II
CPUs
that are designed for 100 MHz bus speed.
Socket 7 CPUs at 83 are easier to handle, so there's
still a
chance of running a Pentium MMX166 CPU at up to 208
MHz and
a PPMT 200 at up to 250 MHz, c't Magazine may scream
and
shout, but ten thousands of people that run 83 MHz
reliably and
stably for months can't just be wiped away and it even
works in
Germany, not only outside this wonderful country.
One last word to the castrated Pentium II 233 and 266
CPUs. This
is the first Intel CPU which is 'assembled'. This
brings the thought
near that the disabling of the higher multiplier was
not done inside
the actual chip package, but somewhere inside the
cartridge. It
could be possible that this castration can be
'reversed' after
openng the cartridge and finding the right spot. If
anyone of you is
willing to try ... let me know and I'll publish it.
It's just a damn
problem to open that %^&*$#@ cartridge ...
And What about the Others ... ?
================================
Well, what about the AMD K6 and the Cyrix/IBM 6x86MX ?
If you
let me start with the 6x86MX, I have to tell you that
especially
Cyrix is selling their 6x86MX chips pretty close to
the margins, as
well known from the past already. They came up with
the - with all
due respect - crazy idea of selling parts with
different specs under
the same name. You can get PR166 CPUs at 2x66 and
2.5x60
MHz, PR200 CPUs at 2x75 or 2.5x66 MHz and PR233 CPUs
at
2.5x75 or 2x83 MHz. These CPUs with the same P-rating
are
actually not performing equally, but who cares? Now I
came
across cases where you couldn't even clock a PR200 CPU
at
2x75 MHz to 2.5 x 66 MHz, which is slightly faster.
Hence forget
about overclocking unless you got a nice PR233 at 2.5
x 75 MHz,
since then you might have a chance. IBM is
unfortunately under
the threat of conformity with Cyrix and rumors say
that IBM is
selling their chips the same way against their own
believe ... well,
well.
This leaves AMD's K6 as the only real overclocking
champ and
as long as your K6 is real, you've got a good chance
to overclock
which ever way you like, either with multiplier
increase or with
higher bus speeds or with both. However there's a
little problem.
AMD doesn't seem to care much about the fact that
remarking
their chips can be done by a six year old child.
There's only some
paint printed on the aluminium heat sink attachment,
which you
can wipe off with several different chemicals.
Printing a new
marking on the 'naked' CPU is not too hard to do. This
makes a
K6 233 out of a K6 200 or even K6 166. Be careful with
that,
examine the printing very carefully. If it's done
well, you won't have
a chance though. The incidence of remarked K6 CPUs is
cerainly
higher than you think, and most reports about
'unoverclockable'
K6 CPUs are due to remarked 166 version, marked to a
K6 200.
To archiwum zostało wygenerowane przez hypermail 2.1.7 : Tue 18 May 2004 - 16:39:02 MET DST