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Zalman ZM600 heatpipe-cooled modular power supply

Nov 8, 2006 by Nicholas
Geraedts
with Mike Chin

Product
Zalman ZM600-HP

ATX12V v2.2 compliant power supply
Manufacturer
Zalman
Suggested Price
US $160

Nicholas Geraedts, the newest member of SPCR's Vancouver editorial team, is no stranger to electronics or computers, having tinkered with them for years, particularly the last four in the Engineering Physics undergraduate program at the University of BC. He's been a silencing enthusiast for not quite as long, but is enthusiastic about learning much more and sharing his findings with SPCR readers in the months ahead.

- Mike Chin, Editor

As power ratings grow larger, power supply manufacturers struggle with the battle of heat dissipation.
The common method of tackling this problem is by using standard heatsinks and
fans. Zalman brings another idea to the table — not necessarily a new one, but
one that proves to have some merit — heatpipes. SilverStone used this idea
with their ST30NF Fanless PSU, and came
out with a pretty decent product.

Zalman is a company better known for their heatsinks and other cooling technologies,
and with the ZM600-HP's power output and price tag, it looks like they're taking
a shot at the high-end power supply market. Zalman is no stranger when it comes
to using heatpipes, as we saw with the TNN-500 and the TNN-300
Fanless PC Enclosure System
SPCR reviewed in February 2006. Heatpipes offer
an effective method for transferring heat from one area of a system to another,
provided that the temperature difference between the two is great enough.

APPEARANCES

The ZM600-HP comes in a glossy full color retail box that shows off the high power output
of the device. It also clearly displays the heatsink attached to the heatpipe
within the power supply.



The 600 watt power rating and heatpipes are clearly shown.



No fancy gimmicks inside the box.

The contents of the box are all business. A manual mounting screws, a handy 5V / 12V adapter for fans, and a smaller box contains
the individually sleeved cables. This isn't anything unusual, but it's a
nice touch not having to deal with loose cables everywhere.

FEATURE HIGHLIGHTS

Zalman ZM600-HP Feature Highlights (from Zalman's
web site)
FEATURE & BRIEF COMMENT
Heatpipe Installed for Maximum Cooling Performance and Ultra-Quiet
Operation
Heatpipes have been seen on fanless power supplies in the past. We'll see how well they were here.
Four Independent +12VDC
Outputs
supply power independently to the CPU, VGA, motherboard, and
peripheral components for the highest level of stability and performance.
Most likely, there are four 18A current limiters at specific 12V cable points, all fed from a central 12V line. Independently current limited, but not independent circuits.
Supports ATX12V CPU 4-Pin and EPS12V CPU 8-Pin
EPS12V connectors are
only required for dual CPU systems but the spec is often used for dual video card setups in the absence of guidelines in ATX12V
Modular cables provide
organized cable management and improved air circulation inside the computer
case.
Helps with cable management
inside the case.
Gold-plated terminals minimize power loss by reducing contact
resistance.
How much power is lost
at the connectors?
Dual PCI-E connectors
Necessary for SLI & Crossfire systems.
Multiple Safety Features
-
Over-Voltage Protection, Over-Current Protection, Short-Circuit Protection,
Under-Voltage Protection, Over-Temperature Protection.
Standard on
most power supplies these days
Active Power Factor Correction (PFC)
A boost converter to
maintain a constant DC bus voltage while drawing a current always in phase
with and at the same frequency as the line voltage. Benefits AC power
delivery; reduces input AC current and can allow a smaller UPS to be used.
High Efficiency Design Rated maximum efficiency
is 84%

SPECIFICATIONS

OUTPUT SPECIFICATIONS: Zalman ZM600-HP
AC Input
100-240V ~10A-5A; 50/60 Hz
DC Output
+3.3V
+5V
+12V1
+12V2 +12V3
+12V4
-12V
+5VSB
Maximum Output Current
24A
24A
16A
16A
16A
16A
0.5A
2.5A

Maximum Combined

155W
504W
6W
12.5W
581.5W
18.5W

The 504W combined rating for the +12V rails should be plenty for just about any
system. A dual CPU system with dual video cards might push the ZM600-HP to
its limits, but that would be a feat in itself.

It's important to note that the majority of the power supplied by this system
lies in the 12V lines. The 155W output capabilities of the 3.3V and 5V lines
might not make it a suitable candidate for powerful older systems where the
CPU draws its power from the 5V line.

EXTERNAL TOUR

The exterior of the ZM600-HP is fairly ordinary, but then again, we don't spend
all day looking at our power supply, do we? The case is slightly longer than standard ATX (165mm instead of 140mm), but
you 're not likely to have any troubles fitting this power supply into your system.



Nothing out of the ordinary here.

A single 120mm fan draws air into the power supply from below, and a single
exhaust on the rear of the power supply ensures that all that air passes over
the heatsink. A wire grill protects the fan while providing a low resistance
to the airflow.

The heatpipe design is visible through the rear grille of the power supply.
Maybe this is an aesthetic touch on Zalman's part, reminding the customer of
why they bought this product.



The heatpipe and attached heatsink are clearly visible when viewed from behind.

Aside from the grill of hexagonal holes, the only other opening in the casing is a set of three small slots above the main output cables. Not much heat will be recirculated back into the case through these



There are three types of output connectors for the detachable cables, three 4-pin connectors for standard optical and hard drive power, two 6-pin connectors for SATA power, and one 8-pin for either an extra EPS12V CPU cable or an extra 6-pin PCIe video card power cable.

It is not clear whether each group of outputs is separately current limited. There is no indication at all, either in the manual or their web site, of how the current limits are distributed among the various 12V output connectors.

CABLES AND CONNECTORS

There are a total of seven sleeved cable sets:

Permanently attached:

  • 18" cable for main 20+4-pin ATX connector
  • 18" cable for 6-pin PCIe connector
  • 18" cable for 2x 2x12V CPU2 connectors — the manual states that these cable can be combined to form an EPS12V CPU 8-pin connector

Detachable:

  • 19" cable for 2x 2x12V CPU2 connectors —the manual states that these cable can be combined to form an EPS12V CPU 8-pin connector
  • 18" cable for 6-pin PCIe connector
  • 32" cable with three 4-pin IDE drive connectors
  • 2 x 32" cable with two 4-pin IDE drive connectors and one floppy connector
  • 2 x 31" cables with three SATA drive connectors

The cables come packaged with five velcro straps which should help with cable
management in the system. These cables are not especially long or short.

For those users who like to show off their systems, they will be pleased to
know that all the cables provided are sleeved. This also helps keep things neat
and tidy inside the case, making it easier to maintain good airflow.

It's easy to see that Zalman is targeting the high end market. The ZM600-HP
comes with two PCI-E connectors for gamers who use SLI in their systems. The
two 2x12V connectors can be combined to form an EPS12V connector. This is only
relevant to those who use dual CPU systems, but it doesn't hurt to have it.

One curiosity is the inlcusion of the second 2x 2x12V CPU2 connector. We know the second 6-pin PCIe power cable is useful for dual video card SLI or Crossfire systems, but what kind of system requires four 2x12V or two 8x12V connectors?

INTERIOR

With a typical 600W power supply, we would expect to see some hefty heatsinks,
but with the heatpipe drawing much of the heat away from the main components,
the main heatsinks are quite a bit smaller than usual, and there is quite a bit of free space inside. The components are fairly tightly
packed, restricting airflow, and an empty space at the front of the power supply
might trap hot air.



Tightly packed components might impede airflow.



Heatpipe is placed in the center of the exhaust grille.

The fins on the heatpipe/heatsink are tightly spaced, suggesting the need for
high airflow to provide sufficient cooling. This is definitely not a good thing
for quiet computing. Secondly, the air blown into the power supply is first blown over
the central conventional heatsinks, and then out over the heatpipe attached heatsink.



A closer look at the heatpipe and heatsink.

We know that the previous Zalman PSUs were made by Fortron-Source Power, but surprisingly, the UL file number on the UL/CSA certification sticker is Zalman's own. The primary transformer in the middle of the PSU is marked with the letters SPI, which we know to be the acronym for Sparkle Power Inc, a sister company to FSP. So Zalman remains with the same supplier that they've used since their very first PSU some five years ago.

FAN

The medium speed ball bearing fan is made by Adda, a name found in many of the quietest power supplies
today. We hope that this will help the system stay as quiet as possible, while
still extracting as much heat as possible from the heatsink.



Adda fan adds to the build quality.

TESTING

For a fuller understanding of ATX power supplies, please read the reference
article Power Supply Fundamentals & Recommended
Units
. Those who seek source materials can find Intel's various PSU
design guides at Form
Factors
.

For a complete rundown of testing equipment and procedures, please refer to
SPCR's PSU Test Platform
V.4
. The testing system is a close simulation of a moderate airflow
mid-tower PC optimized for low noise.

In the test rig, the ambient temperature of the PSU varies proportionately
with its output load, which is exactly the way it is in a real PC environment.
But there is the added benefit of a high power load tester which allows incremental
load testing all the way to full power for any non-industrial PC power supply.
Both fan noise and voltage are measured at various standard loads. It is, in
general, a very demanding test, as the operating ambient temperature of the
PSU often reaches >40°C at full power. This is impossible to achieve
with an open test bench setup.

The 120mm fan responsible for "case airflow" is deliberately run
at a steady low level (~6-7V) when the system is run at "low" loads.
When the test loads become greater, the 120mm fan is turned up to a higher speed,
but one that doesn't affect the noise level of the overall system. Anyone who
is running a system that draws 400W or more would definitely want more than
20CFM of airflow through their case, and at this point, the noise level of the
exhaust fan is typically not audible.

Great effort has been made to devise as realistic an operating
environment for the PSU as possible, but the thermal and noise results obtained
here still cannot be considered absolute. There are too many variables in PCs
and too many possible combinations of components for any single test environment
to provide infallible results. And there is always the bugaboo of sample variance.
These results are akin to a resume, a few detailed photographs, and some short
sound bites of someone you've never met. You'll probably get a pretty good overall
representation, but it is not quite the same as an extended meeting in person.

REAL SYSTEM POWER NEEDS: While our testing loads the PSU to full output
(even 600W!) in order to verify the manufacturer's claims, real desktop PCs
simply do not require anywhere near this level of power. The most pertinent
range of DC output power is between about 65W and 250W, because it is the power
range where most systems will be working most of the time. To illustrate this
point, we conducted system tests
to measure the maximum power draw that an actual system can draw
under worst-case conditions.
Our most power-hungry Intel 670 (P4-3.8) processor
rig with nVidia 6800GT video card drew ~214W DC from the power supply under
full load — well within the capabilities of any modern power supply. Please
follow the link provided above to see the details. It is true that very elaborate
systems with the most power hungry video card today could draw as much as another
60~100W, but the total still remains well under 400W in extrapolations of our
real world measurements. As for high end dual video card gaming rigs... well,
to be realistic, they have no place in silent computing today.

SPCR's high fidelity sound
recording system
was used to create MP3 sound files of this PSU. The photo below shows
the setup (a different PSU is being recorded). All other noise sources in the
room were turned off while making the sound recordings.

INTERPRETING TEMPERATURE DATA

It important to keep in mind that fan speed varies with temperature,
not output load. A power supply generates more heat as output increases, but
is not the only the only factor that affects fan speed. Ambient temperature
and case airflow have almost as much effect. Our test rig represents a challenging
thermal situation for a power supply: A large portion of the heat generated
inside the case must be exhausted through the power supply, which causes a corresponding
increase in fan speed.

When examining thermal data, the most important indicator of cooling efficiency
is the difference between intake and exhaust. Because the heat
generated in the PSU loader by the output of the PSU is always the same for
a given power level, the intake temperature should be roughly the same between
different tests. The only external variable is the ambient room temperature.
The temperature of the exhaust air from the PSU is affected by several factors:

  • Intake temperature (determined by ambient temperature and power output level)
  • Efficiency of the PSU (how much heat it generates while producing the required
    output)
  • The effectiveness of the PSU's cooling system, which is comprised of:
    • Overall mechanical and airflow design
    • Size, shape and overall surface area of heatsinks
    • Fan(s) and fan speed control circuit

The thermal rise in the power supply is really the only indicator
we have about all of the above. This is why the intake temperature is important:
It represents the ambient temperature around the power supply itself. Subtracting
the intake temperature from the exhaust temperature gives a reasonable gauge
of the effectiveness of the power supply's cooling system. This is the only
temperature number that is comparable between different reviews, as it is unaffected
by the ambient temperature.

TEST RESULTS

Ambient conditions during testing were 21°C and 17 dBA. AC input was 117V,
60Hz.

OUTPUT & EFFICIENCY: Zalman ZM600-HP











DC Output Voltage (V) + Current (A)

Total DC Output

AC Input

Calculated Efficiency
+12V1
+12V2
+5V
+3.3V
-12V
+5VSB
12.32
0.98
12.32
1.75
5.08
0.99
3.37
0.97
0.1
0.2
44.1
64.6
68.3%
12.37
1.94
12.37
1.76
4.98
1.96
3.31
1.86
0.1
0.3
64.4
88.6
72.7%
12.32
1.94
12.32
3.47
4.98
2.9
3.32
1.85
0.1
0.4
90.4
118.4
76.4%
12.31
3.80
12.31
5.09
5.01
4.69
3.34
3.74
0.2
0.8
151.8
185
82.1%
12.29
5.7
12.29
6.8
5.00
5.56
3.34
4.55
0.3
1.0
205.2
248
82.8%
12.25
7.78
12.25
8.3
4.98
6.46
3.32
4.52
0.3
1.2
253.8
307
82.7%
12.27
9.76
12.27
8.3
5.00
8.85
3.34
6.19
0.4
1.5
298.8
360
83.0%
12.25
12.51
12.25
14.51
4.94
12.13
3.32
10.75
0.6
2.2
444.8
545
81.6%
12.18
18.07
12.18
19.00
4.89
15.64
3.30
13.99
0.8
3.0
598.8
760
78.8%
Crossload Test
11.95
17.7
11.95
18.77
5.12
1.95
3.34
1.86
0.3
0.3
457.1
555
82.4%
+12V Ripple: 9.0 mV @ 150W ~ 18.5 mV @ 600W (Crossload
Test)

+5V Ripple: 2.9 mV @ 150-200W ~ 3.8 mV @ 600W

+3.3V Ripple: 3.3 mV @ 150-250W ~ 5.3mV @ 600W
NOTE: The current and voltage for -12V and
+5VSB lines is not measured but based on switch settings of the DBS-2100
PS Loader. It is a tiny portion of the total, and potential errors arising
from inaccuracies on these lines is


OTHER DATA SUMMARY: Zalman ZM600-HP
DC Output (W)
44.1
64.4
90.4
163.6
205.2
253.8
298.8
444.8
598.8
Intake Temp (°C)
21
22
22
25
27
26
27
31
35
Exhaust Temp (°C)
26
27
28
32
35
36
39
44
51
Temp Rise (°C)
5
5
6
7
8
10
12
13
16
Fan Voltage (V)
5.0
5.2
5.6
6.0
6.5
6.9
7.5
9.5
11.6
SPL ([email protected])
23
24
25
27
29
30
31
36
40
Power Factor
0.96
0.96
0.97
0.97
0.98
0.99
0.99
1.00
1.00

AC Power in Standby: 0.3W / 0.05 PF

AC Power with No Load, PSU power On: 8.8W / 0.76 PF
NOTE: The ambient room temperature during
testing can vary a few degrees from review to review. Please take this
into account when comparing PSU test data.

ANALYSIS

1. EFFICIENCY was very good across the board. At most loads, the power
supply demonstrated an efficiency of 80% of more. At below 100W loads, the efficiency
drops below 80%. Systems that actually require the high power output capacity of this PSU may not get down that low, but for a high efficiency system at idle, the ~70% achieved between 40~70W is not great.

2. VOLTAGE REGULATION was excellent; by our usual tests, none of the
lines fluctuated by more than 3%. Even under crossloading (imbalanced loading), with the 12V lines on maximum load and the 5V and 3.3V lines on just 2A, the voltage regulation
was excellent.

3. RIPPLE

Ripple was well within the limits specified by the ATX standards.
The worst ripple occurred at maximum load, where the +12V ripple reached 18.5mV.
To put that in perspective, the ATX12V spec requires +12V ripple to be below 120
mV.



+12V ripple at full power output. It was low at any load.

4. POWER FACTOR was excellent thanks to the active power factor correction
circuit, staying very close to the theoretical maximum of 1.0.

5. LOW LOAD PERFORMANCE

Standby and no-load performance were both reasonably efficient, with standby
coming in well under one watt, and no-load under 10W. ZM600-HP had no
issues starting or staying powered on with no load applied.

6. LOW AC VOLTAGE PERFORMANCE

The power supply was set to about 75% load with 120VAC through the hefty variac in the lab. The dial on the variac was then set 10V lower every 10 minutes. Since most power supplies are only rated for operation at 100~240VAC, our test calls for a minimum input voltage of 90VAC. However, in this case, we pushed it down to 80VAC.

Low VAC Test: Zalman ZM600 @ 445W Output
VAC
AC Current
AC Power
Efficiency
+12V
+5V
+3.3V
120V
4.54A
545W
81.6%
12.25
4.93
3.32
110V
4.99A
551W
80.8%
12.25
4.93
3.32
100V
5.51A
556W
80.0%
12.25
4.93
3.32
90V
6.20A
564W
78.9%
12.23
4.93
3.31

80V

7.12A

575W

77.4%

12.23

4.92

3.32

The Zalman ZM600-HP stood up to the drops in AC voltage admirably, even when
operating well below its rated input voltage of 100V. Neither voltage regulation
nor ripple changed measurably during the test, and efficiency dropped only marginally
under the most severe conditions. In some other times
that we played with low AC voltages
,we had some fireworks: One unit shut down
as soon at the voltage dropped to 100V; another sparked and failed entirely!

To be fair, these earlier tests were done at 100% load, but the ZM600-HP showed
no sign of struggle even with the AC voltage was dropped to 80V!

7. TEMPERATURE & COOLING

The cooling of the ZM600-HP worked well considering the high power draw of
the test system. Temperature rise remained reasonable until the 200W mark, where
it rose above 10°C. At full load, it rose to 16°C, which is probably to be expected of such a high power draw. With 170W of power being dumped into
the thermal simulation box, a 16°C rise is acceptable.

The internal temperature of the thermal simulation box was somewhat lower than in recent previous tests of power supplies at similar loads. We're fairly sure this is due to the higher fan ramp up speed, and the larger 120mm exhaust fan in the thermal simulation box.

Does the use of heatpipes make the ZM600 a better cooled power supply? It's hard to say. The Antec Earth Watts 430 used the same exact test rig configuration (bigger 120mm fan), and at the same power output levels (150~450W), the temperature inside the thermal simulation box was 3-4°C higher with the ZM600. This is explained by the higher speed and larger size of the fan in the Zalman PSU; it evacuates the heat from the box more quickly, thus keeping the internal box temperature lower. This difference is also seen at the exhaust temperatures. However, the temperature rise through the power supply was similar.

What does all this mean? The Zalman's heatpipe heatsink works, but we cannot say whether it works any better than a conventional heatsink scheme.

One word of warning: Our new test
bench uses a larger 120mm fan that provides a more realistic simulation of the
kinds of low-noise systems that are in use today. As a result of this change, thermal results
are not directly comparable to earlier tests. Previously tested power supplies will likely exhibit a slightly shallower fan speed / temperature curve in the new setup because a bit more of the heat in the box is evacuated by the 120mm fan.

8. FAN, FAN CONTROLLER and NOISE

The fan started at 5.0V, higher than many other quiet power supply fans. The system was easily audible at 1m, but was not unpleasant.
A slight buzzing sound could be heard when there was
very little load on the +5V lines. Applying a small amount of load on the 5V lines
made this buzz go away.

As the load increased, so did the fan voltage. One would hope that the fan voltage remain constant at low loads, and rise only
when there is risk of damaging the internal components. With the ZM600-HP, the
fan voltage increased more or less linearly, as did the noise levels. At 200W,
the noise levels were 29 [email protected] , which is already a bit too high a value for a quiet system. With the other noise sources in a typical PC, the net SPL would certainly climb over 30 [email protected] with this PSU at this load. This is considerably noisier than the best quiet high power power supplies SPCR has tested.

As any change to airflow also affects noise, the same caveat as the temperature data applies to our
noise results: They are not directly comparable to earlier
reviews. We do not believe that the change is large, but the larger fan will
certainly have an effect; the increase in airflow can be expected to delay the
point when the fan increases in speed. Cooler temperatures inside the test bench
mean that the power supply doesn't have to work as hard to keep cool, and it
can therefore run more quietly. Another possible change is
that the larger fan may let out more noise from the box than previously.

9. PROTECTIVE SHUTDOWN

During testing, the system simply shut down when we were testing it at or close to the
maximum load. This happened a number of times, with the unit coming back on immediately when reset or with a very minor reduction in 12V load. It was undoubtedly the result of the current limiting on the "four independent lines". We have only two independent loads, one for 12V1 (main ATX cable and 4-pin peripheral power cables) and one for 2x12V, so at maximum load, we had 18A and 19A on those lines. Zalman cites 16A maximum on each 12V line. We expect that Intel's ATX12V v2.2 guide of 18A current limiting for the 12V lines was used.

The good thing is that the 12V overcurrent protection circuit definitely works. The bad thing is that the OCP works, so this means if you do have a high power system, you'll have to take some care to distribute the 12V load evenly. You may have to experiment with different cable combinations to avoid this issue with very high power systems.

MP3 SOUND RECORDINGS

Each of these recording have 10 seconds of silence to let you hear the ambient
sound of the room, followed by 10 seconds of the product's noise.

No recordings were made at higher levels; it got a bit too loud.

Sound Recordings of PSU Comparatives

HOW TO LISTEN & COMPARE

These recordings were made
with a high resolution, studio quality, digital recording system, then
converted to LAME 128kbps encoded MP3s. We've listened long and hard
to ensure there is no audible degradation from the original WAV files
to these MP3s. They represent a quick snapshot of what we heard during
the review. Two recordings of each noise level were made, one from a
distance of one meter, and another from one foot
away.

The one meter recording
is intended to give you an idea of how the subject of this review sound
in actual use — one meter is a reasonable typical distance between
a computer or computer component and your ear. The recording contains
stretches of ambient noise that you can use to judge the relative loudness
of the subject. For best results, set your volume control so that the
ambient noise is just barely audible. Be aware that very quiet subjects
may not be audible — if we couldn't hear it from one meter, chances
are we couldn't record it either!

The one foot recording is
designed to bring out the fine details of the noise. Use this recording
with caution! Although more detailed, it may not represent how the subject
sounds in actual use. It is best to listen to this recording after you
have listened to the one meter recording.

More details about how
we make these recordings can be found in our short article: Audio
Recording Methods Revised
.

CONCLUSIONS

The ZM600-HP is clearly targeted at the high performance gaming market. The
high power output, good voltage regulation, and excellent power factor correction
make it a solid candidate for a new dual core, dual video card setup. The price
tag also matches that of systems that might have such a high power requirement.
The modular sleeved cables are also another nice touch for those that demand
tidyness or want to show of their rig to their gamer friends.

Unfortunately, a gaming rig is typically not the realm of quiet computing. The unit
performed quietly only at <150W load, and would most likely be amongst
the loudest components in a typical "quiet" system. It's strange,
since Zalman's product pages are littered with talk about "ultra-quiet"
systems — maybe they're talking about ultra-quiet relative to the typical high-end
gaming rig. Their ZM460B-APS power supply boasts a feature Zalman calls CNPS
(Computer Noise Prevention System) that is supposed to keep the fan running
slowly until the internal temperatures
reach 30°C, but the ZM600-HP has no indication of such a feature on their
website. Our results suggest that the absence of such a claim is no accident.

One possible source of the problem lies in the tight spacing of the heatsink
fins on the heatpipe. With such a small gap between the fins, the fan needs
to spin faster in order to provide sufficient pressure to sufficiently cool
the device. For high airflow systems, this provides more efficient cooling,
but it significantly reduces performance in low airflow situations. Although the heatpipe heatsink is interesting, it has not helped Zalman to produce a PSU that uses less airflow for cooling. Or one that's quieter than the competition.

In the end, if the ZM600-HP is used in a system where the CPU fan, hard drives and/or graphics
card are loud, then yes, you could call this PSU "ultra-quiet".
If silence is your goal, there are several other PSUs even in this high power category that are better choices.

*

SPCR Articles of Related Interest:

Power Supply Fundamentals & Recommended
Units


Power Distribution within Six PCs

SPCR PSU Test Rig V.4

Enermax
Liberty EL500AWT & EL620AWT


Seasonic M12-700

Seasonic S12 Energy Plus: Efficient Power for Connoisseurs

* * *

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this article in the SPCR Forums.

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