🚀 go-pugleaf

>>>>> On Tue, 5 Jan 1993 19:04:34 GMT, khor@bnr.ca (Kyle Hor) said:
Kyle> In article <1icegqINN7vl@savoy.cc.williams.edu>, 93gke@williams.edu (oldwanda) writes:
Kyle> |> If this is true, then how can vendors push the 25Mhz chips to 33Mhz?
Kyle> |> Wouldn't they fail at the higher speeds since they were slow in
Kyle> |> testing?
Kyle> |> 
Kyle>  
Kyle> 1st there is a guard band.  I.e. a 25MHz grade are usually tested to pass
Kyle>  
Kyle> 2nd, there are numerous test on different parts of the chips switching
Kyle> speed.  Again, not knowing the 486 intimately, let's assume there are
Kyle> 100 such tests.  Maybe 99 of them meet the 33MHz grade but one of them
Kyle>  
Kyle> 3rd, semiconductors are sensitive to temperature.  The chip is
Kyle>  
Kyle> Finally, if Intel has a huge order of 25MHz and have a huge stock of
Kyle> 33MHz, they would simply re-mark the chips as 25MHz and ship it.  This

In this case why Intel doesn't sell 33MHz CPUs at 25MHz's price ?
(for the vendor who gets larger amount of them only, of course)

But I can say also 2 reasons for which 25MHz chip can work at 33:
1st, a reason to say 33MHz is too much for it may be heating - higher
  clock rate means more heat and it may destroy chip at full speed
  and maximum ambient temperature simultaneously; but a vendor can
  add heatsink to it or give good cooling to prevent destroying.
2nd, and seems no one said it: test is done at some output load
  (a capacitance connected to every pin), and a chip can be to slow
  with this load (for example, the output current from it is not
  sufficient to load the capacitance in required time); but a vendor
  can put chip on board where capacitances are less than those used
  by Intel's test (the capacitances also affect chip heating).
Anyway, to make sure computer made this way is reliable must measure
a lot of parameters or consult Intel to know e.g. reducing load
capacitances by 40% or reducing ambient temperature by 35 degrees
allows to use 25MHz chip at 33MHz. But the only reason for vendors
to do it is honesty. Or, more precisely, might be honesty if there
were honest businessmans (but I don't know about any).
Jerzy Tarasiuk
"Cannot serve to two masters - God and money - simultaneously."