----- Original
Message
-----
Sent:
Thursday, April 18, 2002 12:48 PM
Subject:
[ukha_d] Overclocking (was New PC recommendations)
-----Original Message-----
From: Andy Bovingdon [mailto:bov@xxxxxxx]
Sent: 17 April 2002 09:09
To: ukha_d@xxxxxxx
Subject: Re: [ukha_d] New PC recommendations
> In addition to an Athlon XP
processor,
think about 512Mb RAM (don't
> bother about the Corsair stuff
unless
you want to overclock - and you
> won't need to unless you want to
run
the latest games - I run a very
> processor intensive simulator for
my
helicopter so I run an XP1500 at
> the same speed as a
1900)
How
do
you actually go about overclocking? Apart from ensuring
the
chip
is
kept cool?
Overclocking
is based on the premise that with adequate cooling processors can be run at
far
faster than the rating printed on them. This is for two reasons – in
your
average office where vents are typically blocked and pretty average cooling
systems are employed processors need to run at the rated speed while they
are
pretty hot – reduce the temperature of the CPU and you can get more
speed
out of it. The other one is that when the factory makes chips it
doesn’t
set out to make say 2000 chips one day and 1800 chips another. It makes
chips
and puts them on a test rig to see what speed they can get out of them.
Generally all chips from the same batch of silicon will generate roughly
the
same speed. Now it gets more complicated, because one particular batch may
be
more than capable of running at 2000 speeds, but there may be demand for
say
1800s. These chips will be marked as 1800s and then copper links on the
surface
of the chip cut to set the speed of the chip electronically. Whether you
get a
good 1800 capable of running at much higher speeds or an average one is pot
luck. Overclocking used to bring with it massive cost savings (in the case
of
486 processors), now it doesn’t yield as much of a saving, people
tend to
overclock “because they can”.
It
actually gets more complicated with each iteration of processors. AMD and
Intel
really don’t care about people at home overclocking chips, what they
don’t want is some Far Eastern bucket shop re-marking chips and
selling
1600s as 1800s. To this end they make it more and more difficult to
overclock
each time the hobbyists find a way to circumvent the protection they build
in.
There
are two methods to overclocking – the first and easiest is simply to
turn
up the bus-speed in the bios (most Abit and Asus boards amongst others will
allow you to do this) so that instead of running at 10x133 (1333MHz) you
run at
10x140 say (1400MHz). This means that you’ll be running everything
though
at faster than its rated speed – PCI bus, AGP, and most importantly
the
DDR memory bus (which is already running at twice the speed of the PCI
bus!)
Manufacturers of performance hardware realise this, and so produce DDR ram
rated at faster than the stock 266MHz. My Corsair ram is rated to 333MHz,
and
is actually capable of running reliably at 360MHz.
The other, more complicated method
involves
keeping the bus speed set to standard and changing the multiplier in the
bios.
AMD and Intel don’t want you to do this so they build a number of
bridges
into the processor to lock in the multiplier marked on the
chip.
My
current processor is an AMD so I only know how to unlock recent versions of
their chips. It used to be relatively simple use a pencil to join up all
the
relevant links – these are the same links that AMD join on the test
rig
so they can set the multiplier in software to find the maximum speed the
processor can reliably run at. Then the pencil line didn’t reduce the
resistance
enough, so people started to use conductive paint for repairing PCB traces.
In
the latest generation of Athlon XP processors AMD cut through the top layer
of
substrate with a laser. Beneath this substrate lies a conductive grid
–
if the conductive paint gets into this grid it really screws with the
multipliers you can set – and in some cases you’ll no longer be
able to run at the speed you could before you started.
The
answer is to fill these holes with something before you start (I used 30
minute
epoxy) and then join up the dots. They are tiny so need masking off with
tape
before you paint on the silver lacquer with a pin!
You’re
now in a position that you can set any multiplier and clock speed, you
like.
The best position is to run the lowest multiplier and highest bus speed
that
you can. This determines the bandwidth between processor and main
memory.
There’s
more, but I’ve spent more time typing this than I originally
intended.
Tim.
For more information: http://www.automatedhome.co.uk
Post message: ukha_d@xxxxxxx
Subscribe: ukha_d-subscribe@xxxxxxx
Unsubscribe:
ukha_d-unsubscribe@xxxxxxx
List owner:
ukha_d-owner@xxxxxxx
Your use of Yahoo! Groups is subject to the Yahoo! Terms of
Service.