E.U.N.U.C.H. (Overclocking in the old time)

From: Hans Franke <Hans.Franke_at_mch20.sbs.de>
Date: Thu Nov 18 11:19:47 1999

> > > For laughs I've been running a 486dx/33 (intel) at 66mhz in a dell box.
> > > The only mod if the heat sink is a moose I had and its attached to the
> > > chip using a BEo filled thermal epoxy. Runs cool and it's solid.
> > 486dx33 at 66 MHz ? Well, I don't want to be picky, but wouldn't
> > this result in 66 MHz CPU bus ? Sounds a bit off for 486 Boards.
> ISA not PCI. The bus is still cpuclock /n and n in that case is 8.

Well, I wasn't talking about the I/O bus (as ISA or PCI should
be considered), but rather about the CPU bus - and if you overclock
an (non multiplieable) basic 486DX CPU, the only way is to raise bus
speed - and 66 MHz is way out of Spec for all 486es I know - regulary
only the AMD Parts are speced for 40 or the old Intel DX50 (was quite
a beast - just _way_ expensive, and rarely seen - I guess the yield
was just to low to promote it).

> > > I've tried that in a socket5 Mb I have using a 486dx2/50 at 100mhz, seems
> > > fine after three months. The cooling is not big a problem.
> > Jep, the most notable CPU is still the AMD 5x86 (486dx4/133 with
> > extended cache) - I have them running at 4x40 MHz == 160 MHz without
> > any problem - only for high load apps the cooling must be presen,
> > a Linux (web) server can even run without a fan.
> I have about 8 of them running here at work including one as a NT3.51
> server all at 133mhz. Very good machines!

Jep. And running at 40 MHz bus speed still comperable to any P100

> > I found it hard to run NMOS 6502 on more than 1.3 times their nominal speed.
> The 8085s and z80s would run that fast but things like propagation times
> don't shrink so the access times and all do not scale well. For example
> take a 4mhz z80 to 6mhz and you better have memory that is faster than
> what would be needed first at glance. Same thing pushing 8085H-2 (6mhz,
> to 8mhz).

True. But for the 6502 even more the CPU itself was often the hardest
part to tweak. Geting fast Memorys wasn't that problem - the CPU itself
starts to malfunction, possibly the propagation times within the CPU
where already stressed.


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Received on Thu Nov 18 1999 - 11:19:47 GMT

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