At 17:12 -0800 11/20/2005, Will S wrote:
For the record Powerlogix also made a carrier card but not as
adjustable for fine
tuning and the cards seem weaker in a number of ways. I think Jeff W may of
played with one fairly recently. best of luck Will S
I recently played with a PowerLogix ZIF card and a couple of XLR8 ZIF
carrier cards. I didn't use anything faster than a 466 MHz G3 ZIF
with them and it's a Rev. 2.x G3 chip so it only supports up to 8X
multipliers. You need a Rev. 3.x G3 chip to get the 10X multiplier.
I only had one example of the PowerLogix carrier and that came out of
a bin at Goodwill, so it may not be representative. I found it
difficult to get any stable configuration above 50 MHz using the PL
card. It is also, as Will mentioned, less adjustable. It has all
the bus multiplier settings, but the bus speed settings come in
increments of 2.5MHz and from 55 - 60 it's a 5 MHz jump, there is no
57.5 MHz setting. IIRC, Mike at XLR8yourmac.com was able to use his
PowerLogix carrier at up to 60 MHz.
Looking at the power supply circuitry on the PowerLogix, it looks
much less robust and probably less capable of delivering stable power
than the PS circuitry on the other cards. There is the equivalent
of a Beige G3's VRM on each Carrier card, but the PL card seems
lacking in capacitors which smooth power to a more constant level.
IIRC, the NewerTech actually uses a plug-in VRM for that part of
their circuitry. At least a prerelease model that was reviewed did.
I have three of the XLR8 cards. They all behaved about the same for
me, which means that none of them were stable beyond about 53 MHz bus
speed. I'm running at 51.6 for a little margin. This was a little
disappointing to me, as I've run this S900 motherboard at 60 MHz and
a little beyond using a PowerLogix PowerBoost Pro 604e card. I was
frankly surprised because of Will's better experiences, and I think
that Mike at XLR8yourmac.com was able to run his XLR8 card at up to
55 MHz. Because I only have an 8X multiplier available, I'm running
this 466 MHz ZIF at 413 MHz.
I have not tested this motherboard with the PowerBoost Pro card in at
least a year. Perhaps there's been some wear to my CPU socket. The
motherboard is mounted vertically in a tower case and there's no
support for the top edge of the CPU card, so the leaning could be
affecting the socket. Or it could just be that some batch of XLR8
cards just aren't as fast as others. I tried this with a couple of
different ZIF cards, but that really shouldn't be a factor, since
they run at 66 MHz or better in Beige G3s.
Anyway, the other thing I found about the XLR8 card is that there are
a ton of undocumented bus speed settings. In general, the ones in
the chart they provide should be sufficient, but the card is
adjustable in something like .2 or .3 MHz increments from about 25
MHz up to 75 or beyond.
Ah, here's the text of a message I sent to Mike, which he never used, AFAIK:
=============================================
The XLR8 instructions list integer and integer + .6 MHz bus speeds.
However, it appears that the Carrier ZIF is settable in .2 MHz
increments.
Switches 1 - 4 control the fine speed settings. If you imagine them
as the digits of a binary number, with 1 most significant and 4 least
significant, you can set any bus speed multiple of .2 MHz from 0 to 3
MHz (15 X .2) + the coarse speed setting.
So for example OFF, OFF, OFF, OFF (all OFF) is 0 X .2 = 0 MHz plus
the coarse speed setting (switches 5 - 8).
OFF, ON, OFF, ON (2,4 ON) = 0101 binary = 3 decimal. 3 X .2 = .6 MHz
plus the coarse speed setting.
ON, OFF, OFF, ON (1,4 ON) = 1001 = 9 => 1.8 MHz + Coarse Setting.
Etc.
The coarse speed settings (switches 5 - 8) seem to be in 3.2 MHz increments.
OFF, ON, OFF, ON (6, 8 on) = 41 0101
OFF, ON, ON, OFF (6, 7 on) = 44.2 0110
OFF, ON, ON, ON (6,7,8 on) = 47.4 0111
ON, OFF, OFF, OFF (5 on) = 50.6 1000
etc.
--------------------------------------------------------------------
That's the gist. The stuff below is examples that drag on for a bit.
In equation form: 25 + 3.2 * (5 - 8) + .2 * (1 - 4) = bus speed;
where (5 - 8) and (1 - 4) are four digit binary numbers represented
by the corresponding switches, where a switch set to 'ON' is a 1 and
a switch set to 'OFF' is a 0.
So, for example, if you wanted 54.8 you solve the above equation (or
read the XLR8 table and adjust your switches up or down a couple of
binary values). 54.8 - 25 = 29.8. 29.8 / 3.2 = 9 + a remainder so
set switches(5 - 8) to 9. This is 1001 or switches 5 & 8 ON. That's
our coarse setting. 25 + 3.2 * 9 = 53.8 so we still have 1 MHz to
go. 1 / .2 = 5 so switches (1 - 4) need to be set to 5 or 0101 which
is 2 & 4 ON.
So 2, 4, 5, 8 should yield 54.8 MHz. Filling in the equation above
just to expand the example we have 25 + 3.2 * (1001) + .2 * (0101) =
25 + 3.2 * (9) + .2 * (5) = 25 + 28.8 + 1 =
54.8.
One could more easily arrive at this conclusion by noting that 54.6
on the XLR8 table is switches 2,5,8. Adding 1 to the value of the
fine settings simply means turning switch 4 on, so 2,5,8 => 54.6 and
2,4,5,8 => 54.6 + .2 = 54.8 MHz.
I imagine that speeds below 40 and above 66 are accessible and
predictable using this system, though not very useful. :-)
Jeff Walther
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