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Last updated: 2/10/2000

POWER SUPPLY AND COOLING.  This case  does a superb job of cooling a fully loaded, top-of-the-line computer.  In addition to the fan in the power supply, it comes with two chassis fans.  The first one is an 80 mm muffin fan which is fastened with screws to front of the metal chassis.  The second is harder to see in the picture of the case laying on its right side on the preceding page, but it is another 80 mm fan screwed to the chassis above (to the right of) the power supply.  This should cool about anything you can stick in this computer; but, for the fanatic out there, there is a place to mount another 50 mm fan right above the keyboard.

The chassis fans connect to power supply connectors.  It would be better if three-wire fans with RPM sensor circuits were supplied so they could be plugged into motherboards with a system monitoring function.  If such fans are supplied in the future they should include adapters to connect them to the power supply in systems with motherboards without 3-pin connectors for chasses fans.

The diagram to the right came out of AMD's Athlon Processor Thermal Solution.  It looks like the AT900 except the AT900 has some space above the power supply and more around the drive bays.  I will note that the power supply in the diagram exhausts air from the chassis like the 282 and does not direct it in and towards the back of the motherboard for CPU cooling as preferred in the ATX specification--it's no big deal and, maybe, in comparison to this scheme, sucking air in is a bad idea.  Now add the two chassis fans...  The chassis fan in the lower left corner pushes air into the chassis and the one in the upper right corner helps the power supply push air out of the case. You can't get much cooler than this without resorting to refrigerants.

The chassis fan at the rear of the case fits snuggly against the chassis.  The one at the front rests on four dimples where the mounting holes are and has a gap between it and the chassis.  Better air movement into the case could probably be achieved if the front fan had no air gap between it and the chassis; however, I won't attempt to second guess the engineers on this one since the dimples were apparently intentional and integral to the design.

I think it would be a good idea to start designing cases with a filter at the lower left corner in the above diagram and between the plastic and metal to trap dirt that will be sucked into the case from the bottom, especially if the case is put on the floor.  Also, case manufactures, etc. could make some extra money selling filters...

This case comes with a 250 Watt ATX power supply.  In addition to the ATX logical on/off switch on the front panel, which connects to an ATX motherboard, there is a separate power switch on the back of the power supply.  This switch overrides the one on front panel and is handy for making sure power to the motherboard is off, without having to pull the power cord, when plugging-in expansion boards, etc. It is of no great significance during day-to-day operation of the computer.

The logical on/off switch clips to the front of the chassis.  My hat off to A-Top's overworked "spring" designer on this one.  The switch is really easy to replace and it attaches to the chassis about as good one attached with screws.

I counted one 3 1/2" and only four 5 1/4" power connectors, three fewer than the number of drive bays.  At the least, there should be one more 3 1/2" connector.

DRIVE BAYS.  The case has eight drive bays: two exposed and two hidden 3 1/2" bays and four exposed 5 1/4" bays.  All of the exposed bays come with snap-on dust covers.  Other than the kind that are attached with screws, I have never seen drive bay covers snap into place as firmly as these do.  They are somewhat difficult to remove and require a firm whack to install, but you can bet one of them isn't going to accidentally get pushed into the case. This case uses metal rails for all of the drives.  I dislike rails.  They cost more than screws and screw holes.  They take longer to install.  There is no rail standard.  You can't find them when you need them.  Vendors forget to, or purposely do not give extra rails to their customers.  When customers do receive them, they often lose them.  Altogether, over the last 13 years, I have spent man-days searching through my big box of rails trying to find a set to match a customer's computer...

EXPANSION BOARD SLOTS.  The case has seven slots.  It will accommodate motherboards with 1 ISA, 4 PCI, one shared ISA/PCI, and one AGP expansion board connectors, or other combinations thereof.  The slot dust covers are similar to those found in the Enlight cases I've seen.  They have a continuous row of spring-like fingers all along both sides of the covers.  I don't like them.  They are difficult to remove, less than easy to install, and too easily bent, but no big deal.

HARDWARE.   An adequate assortment of hardware was included with the case, but I have seen better.  The speaker is mounted on the inside of the front of the chassis and above the chassis fan where the wires are less likely to get broken (I had to put this somewhere).  It would be nice if some zip-ties were included.

PACKAGING.  The case came wrapped in plastic and packed in a thick cardboard box.  The styrofoam packing was better than the last A-Top case I reviewed and on a par with the AOpen cases.

DOCUMENTATION.  There was a one-pager with the case.  Its not very good, but more than what came with the last A-Top case I reviewed.

BOTTOM LINE.  This AT900 is certainly a better quality case than the A-Top AT589 translucent case reviewed some time ago.  I would subjectively rate the quality of the AT900 in the same league as the AOpen HX45A, but not as high as the Antec KS282 or AOpen HX08.  All three cases are fairly close in quality.  Subjectively (my taste), the AT900 appearance (style) is a little better the HX45A, is about as good as the HX08, but not as good as the KS282.  The AT900 beats the HX45A in that is has two chassis fans, two more drive bays, and better ventilation.  It beats the KS282 with included chassis fans and two more drive bays.  It is smaller, lighter, less expensive, not as hefty,  and has five fewer drive bays than the HX08.  It has two open three-inch drive bays like the HX45A. The HX08 and KS282 only have one, a negative if you want to install a Zip drive without using a mounting kit.  The removable motherboard drawer is a plus for some buyers.  A big plus:  A-Top will pay for the shipping if you buy it direct from their Web site.

DIMENSIONS:  17"(D) x 7 1/2"(W) x 21"(H)

WEIGHT: Net 24.8 LBS/11.25KG; Gross 27.6 LBS/12.5 KG/


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