At 02:12 PM 6/03/97 -0600, you wrote:
>At 10:14 PM 3/6/97 +0300, you wrote:
>>What happens if I use a 30MHz crystal with a 16c84 (10MHz max?)
>
>I haven't been able to push the '84 past about 16MHz.  Past that and it
>fails entirely.  of course, for a product for resale you would actually want
>to stay right near the rated 10MHz spec.
>
>It is possible, you know, to port '84 code to something like a 16C554; these
>can be run up to 20MHz and I suspect some might operate at up to 30MHz, but
>I'd hate to rely on that for a product.  Would 20MHz suffice?
>
>Also, you might have better luck with the high speeds using a TTL oscillator
>as opposed to a crystal.  I am not sure, but it might be worth a try.
>-Todd

In the very old days of the MC1468705F2S which had a linear relationship between
clock frequency and voltage - we found we could proportionately up the frequency
at higher voltages.

A 5v regulator had a diode (pointing) to ground (cathode) so it would raise the
5v reg o/p to about 5.75 volts. This would give us a bit more by the ratio
5.75/4.75 times the clock - then we would select the best ones to go a bit
higher
still (Oh 4.75 was a better fit than 5.0v).
(PS we also put a 4K7 resistor between 5v o/p and anode of diode, which made the
o/p voltage a bit more steady at varying temperatures).

Funnily enough this also seemed to work on the MC68705P3S even though this was
an HMOS and not CMOS device - we could happily run this at 6.5v without any
failures - though it ran quite warm at 2 Mhz (It was a 5v device and very
robust).

Rgds

Mike

Anybody got internet via cable TV fibre optics - yet ?

Some say there is no magic but, all things begin with thought then it becomes
academic, then some poor slob works out a practical way to implement all that
theory, this is called Engineering - for most people another form of magic.
                                                                       Massen