Overclocking the inexpensive AMD TBred-B Duron
(3) AndyB
24 Aug 2004
Faster: 2.4GHz at 1.83V Vcore
Strictly speaking, we don't need the Mobile mod for 2.4GHz (in fact you
should remove it), but we are going to
need the following:
A better heatsink/fan. I used a Zalman CNPS7000A-AlCu for my
tests.
A 1.6GHz Duron manufactured in Q2 2004 or later. AMD must have
been
optimizing their manufacturing process lately because the more recent
Durons will reach 2.4GHz at 1.85V stable, whereas older ones previously
wouldn't.
So now you know, Durons are like oysters: they must be bought fresh!
Since the 1600MHz Durons already have a multiplier of 12, we don't need
the Mobile mod this time.
I used this Duron, marked 0420:
I also used a K7S8XE+ mainboard mounted
in an Enermax case:
And it worked quite well. I actually installed a Linux Mandrake 10.1
Beta1 distribution, and here is how the Linux kernel reports this
processor:
One of the programs I always use to test for stability is Memtest86:
Temperatures and voltages can be checked in the BIOS:
How high can we go, on simple air cooling, with these inexpensive
TBred-B Durons?
Fastest: 2.5GHz at 1.91V Vcore with the Mobile and L6 mods
We want to get up to 12.5 x 200MHz = 2.5GHz core speed. The first
problem we must solve is that the TBred-B cores are all superlocked,
and that includes the Durons. So we have to use the Mobile mod as
explained above. The second problem is that the Beta
K7S8XE+ Multiplier Control BIOS found at OCWorkbench will not work
with Durons. So the only thing we can do is to use the information we
found at the Fab51 website
and try to work out a solution.
The solution that I am going to use is the same that Eversor used in
the article linked above, which is to mod the L6 bridges. Quoting from
the Fab51 website,
the "L6 bridges are not used in CPU
of the desktop version. They are all closed. In the motherboard
corresponding to mobile CPU, L6 bridge serves as multiplier rating."
To get a 12.5 multiplier, we can see that L6[0] and L6[1] have to be
cut. To cut a bridge, the best way is to use a cutter with a new blade,
like the one shown above.
Just apply the tip of the blade on top of the bridge, and push a
little.
The green epoxy is very soft and the trace is extremely
thin, so just a small pressure is required to cut the bridge. I am
still keeping Vcore at 1.83V for now.
It boots!
It passes Memtest86!
It locks up loading the Linux GUI...
OK, let's activate our secret weapon, the Omega 13: the over voltage
BIOS option! Now the Vcore is at 1.91V, so just to be on the safe side,
I also increased the Zalman fan speed. And...
It works!! Notice Linux correctly identified the processor as a mobile
Duron.
A kernel compile (practically 100% CPU load, lots of I/O) confirms the
system is stable enough for everyday use...
Conclusion: it was worth it!
We just went all the way from 1.6GHz to an upper limit of 2.5GHz
(better than 50% overclock). And to do so we used the least
expensive x86 CPU and an inexpensive but stable mainboard, not
particularly renowned for its overclocking capabilities. Needless to
say, nothing can match the price/performance ratio of this setup.
Nothing, really?
Some tips
Use good quality thermal compound, and use it adequately (clean
the CPU and HSF carefully, and coat the CPU with a very thin layer
everytime you mount a CPU heatsink/fan).
Overclocking is useless if your system is unstable.
Higher clock rates and higher voltages mean higher heat output:
both case and CPU must be properly cooled/ventilated.
Check and double-check your system everytime before you turn it
on and/or begin disassembling it. Removing a CPU from a "hot" socket
will probably destroy it (yes, it happened to me once).
