Hardware Reference
In-Depth Information
sustain output at the rated level. If your systems draw less than the rated level, you have
some additional time.
Caution
Be careful! Most UPS systems are not designed for you to sit and compute for hours through
an electrical blackout. They are designed to provide power only to essential components and
to remain operating long enough to allow for an orderly shutdown. You pay a large amount
for units that provide power for more than 15 minutes or so. At some point, it becomes more
cost-effective to buy a generator than to keep investing in extended life for a UPS.
Some of the many sources of power protection equipment include American Power Con-
version (APC) and Tripp Lite. These companies sell a variety ofUPS, SPS, line protector,
and surge protector products.
Caution
Don'tconnectalaserprintertoabacked-upsocketinanySPSorUPSunit.Suchprintersare
electrically noisy and have widely varying current draws. This can be hard on the inverter
in an SPS or a UPS and frequently cause the inverter to fail or detect an overload and shut
down. Either case means that your system will lose power, too.
Printers are normally noncritical because whatever is being printed can be reprinted. Don't
connect them to a UPS unless there's a good business need to do so.
Some UPSs and SPSs have sockets that are conditioned but not backed up—that is, they do
not draw power from the battery. In cases such as this, you can safely plug printers and other
peripherals into these sockets.
Real-Time Clock/Nonvolatile RAM (CMOS RAM) Batteries
Most PCs have a special type of chip in them that combines a real-time clock (RTC)
with at least 64 bytes (including 14 bytes of clock data) of nonvolatile RAM (NVRAM)
memory. This chip is officially called the RTC/NVRAM chip , but it is often referred to as
the CMOS or CMOS RAM chip because the type of chip used is produced using a CMOS
Complementary Metal-Oxide Semiconductor (CMOS) process. CMOS design chips are
knownforlowpowerconsumption.ThisspecialRTC/NVRAMchipisdesignedtorunoff
a battery for several years.
The original chip of this type was the Motorola MC146818, which was used in the IBM
AT dating from August 1984. Although the chips used today have different manufactur-
ers and part numbers, they all are designed to be compatible with this original Motorola
part. Most modern motherboards have the RTC/NVRAM integrated in the motherboard
Search WWH ::




Custom Search