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Weekly Tweaks Archive III

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.


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.


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.


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 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.


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.

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.


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 (Mike Echlin's web page)


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.


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.


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.


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.


Standby Mode Control
Sets standby clock speed to fractions of CPU speed, and enables/disables the video.



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Updated 07/06/04

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