4 Jul
2014
4 Jul
'14
2:24 a.m.
In most cases, I find the remarked ICs are actually OK. They're
obviously fakes still (commonly the origin printed on the top is
different to the origin in the casting on the bottom), but functionally
they're fine. This puzzled me initially, but I asked one of the sellers
about this, and he said that it was done because the process of removing
the ICs from the boards often marks or damages the printing. So the
standard process involves remarking, straightening the legs to factory
original angles, and re-tinning. It results in used ICs that look new.
Sometimes they're sold as 'remanufactured' (which is sort of accurate),
other times they're sold as new, which is obviously untrue. I'm not that
bothered so long as they work, though I probably should complain about
it.
On 3/07/2014 9:03 a.m., Tony Duell wrote:
clock (Enable) and the Q clock (Quadrature).
FWIW, the 'clock rate' of
That depends on the circuitry around the CPU.
However, if it sues the
6809E CPU, it's a fair bet it is goign to do
oomething odd with E or Q
> (perhaps stretchign one of them when acessing slower memory or
something). In which case, tryign to use the
plain 6809 is goignt to be
a
This is becoming real
problem. The remarked
devices, of course, have no relation to what they
claim to be, they can't possibly work. Heck, I once enqired about a
replacement for an HP custom IC and was asked 'what package, and how
many pins'. Given this device had only ever existed in one pacakge, with
one particualr pin count, it wa obvious I was goign to get a fake. I do
wonder why they botyher. They can't make that much money selling to
hobyists, surely no commercial company wants such fakes.
> I spent
a while looking
> over the datasheets of the 68B09 as compared to
the
68B09E. It's obvious
> that there's some difference in the way the
timing works, but I haven't
> been able to come to any firm conclusions
what the exact difference is,
> and what purpose it serves. The best I
can
do is that it's related to
> synchronization with some external
devices.
he difference is where hte clock circuitry is.
The
6809 (normal and E_) need a pair of clocks in hase quadrature. The E
the 6809 is specified as the frequency of these
clocks
The 6809
(on E) has an internal clock generator. It can be driven by a
crystal
of 4 tiems the CPU clock rate (soe a
68B09 can use an 8 MHz
crystal).
The E and Q pins o nthe chip are
outputs
The 6809E (E=External) has
no internal clock generator. The E and Q pins
are inputs, to be
driven by an extgernal circuit
that produces the
approrpatie signals
in phase quadrature.
IIRC, i f you use the 6883 SAM (DRAM
controller) you prettty much hace to
use the 6809E. The SAM generates
E and Q, and
expsects to eb able to
> synchroinse the CPU to them.
> So - can anyone explain
> the difference, in terms that aren't too
hard to understand? And - is
> there any hope of modifying a machine
that
would normally require a
>> 68B09E to be able to use a 68B09?
>
lot of owrk. The 6809E was origianlyl chosen for a
reason, after
all (and
I doubt it was cost, the cost of the external clock
curcuit
would
outweight any difference in price of the 2 chips when
new), so
the reason
is more likey that said clock circuit does soemthing
extra
that can't
easily be done wit hthe plain 6809.
-tony