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Weekly Tweaks Archive III
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ISA IRQ 9,10,11
These may be used by the PCI bus if they
are available, so set them as "Used" if you want to reserve them. Some VGA cards like
to use 9, but many don't, so you might save yourself an interrupt.
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Init Display First
Which VGA card, that is, PCI or
AGP you want to be initialized first, for Windows 98 multi-monitor systems (you can use 2 of
each, but you've probably got only one AGP card anyway). Whatever combination you have, the PCI
is treated as the default, which is probably the opposite of what you need, so you can change it
here.
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MMX
This is an extension to x86 code to allow the better
handling of the repetitive instructions typically found with multimedia applications, allowing
parallel processing of many data items with only one instruction, or as many 8-bit instructions
as will fit into a 64-bit register, so video, at least, will be smoother and faster. For example,
normal Pentiums only process 1 pixel per clock cycle, where the 64-bit MMX registers will be able
to handle 8, although a 32 K cache also has something to do with it. MMX also performs many of
the functions of sound, video or modem cards. The MMX processor's core runs between 2.0-3.5
volts, but the output uses 3.1-3.6v (3.3), so motherboards need 2 voltage regulators. Talking of
which, see the chart at the end of the chapter for chip voltages and other settings. MMX uses
Socket 7 and above. Intel chips have 2 MMX pipelines, whereas the AMD K6 and Cyrix 6x86 have only
one, but their MMX registers are in a dedicated
unit, so they only need one cycle to switch to
MMX. On Intel chips, they are integrated into the FPU so you can't do maths and MMX instructions
at the same time, and over 50 instructions are required to change from one function to the other.
So, if you're using 3D video, for example, the MMX instructions produce the speed, but much of
the advantage is lost after the coordinates are calculated by the FPU and the registers have to
be changed over.
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Spread Spectrum Modulated
There are techniques
(developed by the US government, amongst others) for collecting intelligence from PC
transmissions, as microprocessors (and screens) can radiate for some distance-you can expect to
receive a PC's signals for up to ½ mile, and a mainframe's for anywhere between 3-4 (scan the
area between 2-12 MHz).
This setting is for Electromagnetic Compatibility (EMC) purposes.
It reduces EMI radiations by slightly staggering normally synchronous clocks, the idea being to
lower the peak levels at multiples of the clock frequency by sending a wider, weaker pulse - in
other words, the pulse spikes are reduced to flatter curves. It may also stop the sending of
clock signals to unused memory sockets (see Auto Detect DIMM/PCI Clk, below). Some high
performance peripheral devices might stop working reliably because of timing problems.
The
settings could be 1.5% Down, 0.6% Down, 1.5% Center or Disabled (the percentage is the amount of
jitter, or variation performed on the clock frequency). Center means centered on the nominal
frequency. Shuttle recommends 1.5% Down for the HOT631, but others allow enabling or disabling.
The latter may be worth trying if your PC crashes intermittently, as there may be interference
with clock multiplying CPUs that phase lock the multiplied CPU clock to the bus clock-if the
frequency spread exceeds the lock range, the CPU could malfunction. Do not disable if you are
overclocking, which increases radiation.
You may get a Smart Clock option, which turns off
the AGP, PCI and SDRAM clock signals when not in use instead of modulating the frequency of the
pulses over time, so EMI can be reduced without compromising stability. It also helps reduce
power consumption.
Clock Spread Spectrum
See above.
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Decoupled Refresh Option
This is often called
Hidden Refresh. Normally, motherboard DRAM and that on the data bus is refreshed separately. When
this is disabled, the CPU sends refresh signals to both system RAM and the ISA bus; the latter
takes longer because it's running slower. If enabled, the bus controller will perform arbitration
between the CPU, DMA and memory refresh cycles on the bus, carrying them out in the background
(i.e. hidden) so as not to hold the CPU up, and the DRAM controller will sort things out between
the CPU and motherboard DRAM, thus the ISA bus refresh finishes while the CPU gets on with
another instruction.
The problem is that some expansion cards (particularly video) need to
have the CPU handle the first bus refresh cycle. Disable this if you get random characters or
snowy pictures during high resolution graphics modes (you may need to disable Memory Relocation
as well), albeit with the loss of a little performance. This is especially true with S3 801
boards (such as the SPEA V7 Mirage) coupled with Adaptec C cards and Bs fitted with enhanced ROMs
for drives greater than 1 GB.
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CPU-To-PCI Write Posting
Posting refers to the use
of buffers between the CPU and PCI bus, or maybe the PCI bus and IDE interface (depends on the
manufacturer) to help match their relative speeds - they are called Posted Write Buffers.
The idea is that the PCI bus can retrieve data in its own good time without holding up the CPU.
In this particular case, they belong to the Orion chipset.
When this setting is enabled,
writes from the CPU to the PCI bus will be buffered without interfering with reads into the CPU
cache. When disabled (default), the CPU is forced to wait until the write is completed before
starting another write cycle. Sometimes this cannot be used with certain video cards at certain
CPU speeds (just try and see). Not the same as PCI Posted Write Enable, which seems to
buffer data between buses.
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Time Dilation
Now known as the Crouch-Echlin
effect, this refers to time and date instabilities that occur in and beyond 2000 on PCs and other
embedded hardware, although it does seem to have been narrowed down to machines with unbuffered
clock chips or older, badly written BIOSes.. In other words, times and dates have been observed
to intermittently and abruptly leap forward (or backward) when PCs are powered down and/or
rebooted after 2000. In extreme cases, COM ports have ceased to work. For example, one produced a
date in December after 2 weeks into 2000. See
www.intranet.ca/~mike.echlin/bestif/index.shtml
(Mike Echlin's web page)
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Power Management
This is for Green PCs, or those
complying with the EPA Energy Star programs; the intention is to save unnecessary power usage if
the system becomes inactive. Power is reduced automatically to the devices and restored as
quickly as possible when activity is detected (that's the theory, anyway). This is usually done
with idle timing and event monitoring techniques. A Power Management Unit (PMU) monitors
interrupt signals through an interrupt events detector. If it hears nothing for a while, the
system is put gradually and progressively to sleep, in that the longer the time inactive, the
more parts of the system will close down. However, setting all this up in the BIOS only goes so
far - you should do it in your operating system as well (not NT) - certainly, ensure that 95/98's
compatibility with APM 1.0 is enabled through Control Panel.
Choices available range from
simple "dozing" to complete shutdown:
? Dozing slows the CPU down only, to
around half speed.
? Standby shuts down HD and video, or CPU and SCLK (depends on the
chipset).
? Suspend shuts down all devices except the CPU.
? Inactive stops
the CPU, slows the SCLK and powers down the L2 cache.
? HDD Power Down just shuts down
the hard disk.
As with anything, there are industry standards. For energy saving purposes,
these include:
? APM, or Advanced Power Management
Devised by
Intel/Microsoft. This must be active if you want to keep the time and date when the system is
suspended, with power.exe for DOS (try power.drv for Windows) that coordinates BIOS, DOS and
program activity. APM is responsible for shutting the system down on quitting the operating
system, typically Windows '95, and other useful tricks.
? ATA, or AT Attachments Specification
For IDE
drives. Some ATA compliant devices provide Spin down facilities.
? DPMS, or Display Power Management Signaling
Monitors
and cards conforming to this are meant to be matched, as signals are sent between them to put the
CRT into various low power states, which need instructions from the BIOS. These are recognized
power management states:
Run, Standby, Suspend and Off.
Suspend is slower to return to the Run state than Standby, which is regarded as
being temporarily idle. Disable Standby and Suspend if you don't want PM.
? ACPI, or Advanced Configuration and Power Interface
Hashed
out mainly by Intel, Microsoft and Toshiba. This will allow desktop PCs to have instant on, and
be better for voicemail and household device control, as peripherals can be turned off as well as
the main system unit. It will work the other way, too. Only devices with an ACP BIOS later
than Jan 1 1999 are guaranteed to work with Windows 2000. Some BIOSes have their own maximum and
minimum settings for the times allocated, but you may have a "User Defined" option for
your own. More options may be available for SL (low power) CPUs.
SM Out, by the way, means the
System Management Output control pin.
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Smart Battery System
This is where circuitry is added
to a battery pack to allow better power management, battery life and information for the user,
such as time remaining. The battery can talk to the system, and tell it what services are
required (some charging systems depend on battery heat as an indication of charge status). All
this has been formalized into the SBS system, which actually stems from five documents containing
the specifications for the battery itself, host system hardware, BIOS and charging. The
SMBus is a separate bus allowing direct communication between the host and the battery. The Smart
Charger allows a battery to control its own charge, while a Smart Battery Selector is used in
multiple systems to determine which one is in use, which is charging, etc.
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PM Control by APM
Or Power Management Control by
Advanced Power Management.
Switches APM on or off; choices are Yes or No.
If
Yes, combine DOS and Windows utilities for Green Mode (only with S-series CPUs). When
enabled, an Advanced Power Management device will be activated to enhance the maximum Power
Saving mode and stop the CPU internal clock. In other words, the BIOS will wait for a prompt from
APM before going into any power management mode.
If disabled, the BIOS will
ignore APM. You need DOS and Windows utilities as well.
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IDE Standby Power Down Mode
Also known as Hard Disk
Timeout, or HDD Power Down (Award)Allows automatic power down of IDE drives after a specified
period of inactivity, but some don't like it (notebook drives are OK). 15 minutes is a suggested
minimum, to avoid undue wear and tear on the drive. Probably doesn't affect SCSI drives.
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Standby Mode Control
Sets standby clock speed to
fractions of CPU speed, and enables/disables the video.
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