Hard Digital Disk. Protection against Failures. Part II

While analyzing the hard disk reliability, use the parameters that indicate the hard disk aging: an amount of power cycles, an amount of engine’s rotation during operation, an amount of head moving and other.

Modern hard disks are not also able to receive information about the state, for example about the speed of data exchange between the medium surface and disk cache-memory, the search speed and other, but it is able to restore bad sectors independently.

The usage of the hard disk testing (a value “Enabled”) causes the decreasing of a computer’s performance, so it is recommended to use S.M.A.R.T. technology if you use the outdated hard disks or the disks the data on which have sufficient value. In all other cases, this parameter can be switched off (a value “Disabled”) and it should be switched on only if there are some error messages affecting the work of the hard disk.

Hard Digital Disk. Protection against Failures. Part I

Hard Digital Disk (HDD) is the main peripheral device destined for storing large volumes of information.

Any hard digital disk has got a set of characteristics on which the conclusion of its productivity is based: rotation speed, cache-memory volume, searching time, a number of reading heads and other.

Protection against Refusals

The parameter that enables to test the hard digital disk is called “HDD S.M.A.R.T. Capability” (HDD Instant Recovery, SMART Monitoring). It enables or disables to check the opportunity of the hard disks to refuse while booting a system and monitor them during their operation.

S.M.A.R.T. technology (Self-Monitoring, Analysis and Reporting Technology) allows for self-testing and analysis of the hard disk b y providing monitoring of various parameters, early diagnostic and prevention of failures.

For example, using this technology, you may control each head’s fly height over the disk surface, the speed of data transmission, an amount of carry-over sectors and unsuccessful attempts to read or write.

Shadow Memory. Part III

It is also recommended to shadow memory for video-BIOS when you play the DOS-games or call the DOS-programs from more “advanced” operating systems (Windows95 and higher). In this case, your program (or game) directly requests to video-BIOS, bypassing the functional capacities of the current operating system. If the DOS-programs are not used, it is better to switch off the parameter of video-BIOS shadowing.

Except the parameter that offers to shadow the entire memory area, some versions of BIOS use the parameters that enable to shadow some parts of memory. These parameters are completely identical to the parameters described above, for example: Video ROM Shadow C000, 16K and Video ROM Shadow C400, 16K.

To shadow memory for the devices connected to ISA-bus, you may use the parameter “Memory Hole At 15M-16M” (Memory Hole). Using this parameter, an area between 15 and 16 MB, to which the constant memory of the appropriate ISA-devices is shifted, is transferred to operating memory. This parameter may have two values: Enabled and Disabled. This parameter enables to increase the productivity of appropriate input/output devices but locks an access to an appropriate address space for other programs. If this parameter is on, your operating memory actually losses one GB of its volume, so if you do not use ISA-devices or their productivity is not important for you, this parameter should be turned off.

The parameters described above may also have the following values: None – shadowing is prohibited; at 512 kB (512 KB-640 KB, Conventional) – memory shadowing between 512 and 640 KB; at 15 MB (15MB-16MB, Extended) – memory shadowing between 15 and 16 MB.

Shadow Memory. Part II

To shadow the separate memory areas, you may use the following parameters: “C000, 16K Shadow”, “C400, 16K Shadow”, “C800 16K Shadow”, CC00 16K Shadow”, D000, 16K Shadow”, “D400, 16K Shadow”, D800, 16K Shadow” and “DC00, 16K Shadow”. Depending on a version of BIOS, the names of these parameters may be changed, for example “C8000 – CBFFF Shadow” or “Adaptor ROM Shadow CC00, 16K” but all of them describe a particular memory fragment, the volume of which is equal to 16 Kbyte. These parameters may have two values: Enabled and Disabled. The shadow is disabled by default, but if you use some devices with the read-only memory, you must set the value “Enabled” for this parameter. If you use operating systems starting from Windows95 or higher, set the value “Disabled” for all parameters.

The shadowing of BIOS video card is a special case. The recommendations are the same: the usage of shadowing while operating or playing games allows significantly increasing the performance of video card.

To shadow the memory with video-BIOS, use the parameter “Video Shadow” (Video BIOS Shadowing, Video ROM BIOS Shadow, Video ROM Shadow C000, 32K). This parameter may have two values: Enabled and Disabled. But some video cards may locate their BIOS in other areas, so if you do not find the improved quality of video card work, refer to the description of your video card and carry out manual shadowing of the required memory areas using the parameters “C000, 16K shadow” and others.

Shadow Memory. Part I

Shadow memory is the transfer of the content from read-only memory to operating memory. The shadow gives the substantial performance improvements as a request is not addressed to the slow read-only device memory but to its pattern located in the fast operating memory. The simplest example is BIOS parameters which are stored in the non-volatile memory but after switching on a computer they are transferred to an operating memory thus optimizing the configuration of a system.

The shadow is performed in the memory area from 640 Kbyte to 1 MB that is in line with a physical address “a0000h-fffffh”. The shadow mechanism is not very important in modern operating systems – 32-bit system (Windows95 and higher) do not operate with the shadow device memory but directly with the drivers booted in operating memory.

Nevertheless, you may specify the necessity to shadow some parts of system memory such as network or video cards and other in old computers that use the intellectual devices. Such procedure is especially useful for 16-bit systems – MS DOS and Windows 3x.

All BIOS parameters for shadow memory are located in the sections “Chipset Features Setup”, “Advanced Chipset Features” and “Advanced”.

 The shading of operating memory for system BIOS is executed using the parameter “System BIOS Shadow” (System Shadow, System ROM Shadow F000, 64K). This parameter may have two values: Enabled and Disabled.

Direct Memory Access. Part III

The devices located on ISA-bus actively use the Direct Memory Access, so to allocate DMA-resources among ISA-devices, use the parameter “DMA n Used by ISA”, where n – a number of a channel (from 0 to 7). This parameter may have the following values:

  • No/ICU – is not used. This value points that this channel is exempt and can be allocated by BIOS. This channel also can be set using a special DOS-program “ISA Configuration Utility” (ICU).
  • Yes – is used. This channel is forcibly exempted for ISA-device that does not support the Plug and Play technology. This value allows preventing the automatic assignment of channel from another ISA-device that supports the Plug and Play technology.

ISA-bus is hardly used in modern computers so the manual allocation of channels and their setting are not required. But it is possible to optimize the operation of some frequently used devices, for example LTP printer port, that provide the direct memory access by minimizing delays.

To do this, use the parameter “DMA Wait States” that enables to set an amount of waiting cycles before the transmission of data via DMA-channels. This parameter may have the following values: 1T, 2T, 3T and 4T (in cycles). The decreasing of value causes the increasing of speed but in some cases this may cause some failures. Besides, you may use the parameters “8-Bit DMA Cycle Wait States” and “16-Bit DMA Cycle Wait States” which enable to set the delays for 8-bit and 16-bit DMA-channels separately. The first four DMA-channels (from zero to three) belong to the 8-bit channels and the next four (from four to seven) – to the 16-nit ones.

Direct Memory Access. Part II

All parameters that enable to allocate channels of direct memory access, as well as all parameters of allocation of interruptions, are located in a section “PNP/PCI Configuration BIOS”.

Use the parameter “DMA n Assigned to” (DMA Resources, DMA Channel n) for manual allocation of DMA-channels, where n – a number of assigned channel (from0 to 7 inclusively). The descriptions of device types that must be connected to the particular channels are used as the values of this parameter.

  • Legacy ISA (ISA/EISA) – a channel for ISA-devices that do not support Plug and Play mechanism. A channel for such devices is set manually using a switcher.
  • PCI/ISA PnP (PnP) – a channel for PCI and ISA-devices that support the Plug and Play mechanism.

Except the above parameter, BIOS may use an identical parameter “DMA n Type”, where n – a number of assigned channel (from 0 to 7 inclusively). This parameter may have the following four values: Normal ISA – ISA-device that supports the Plug and Play mechanism; PC/PCI – PCI-device that supports the Plug and Play mechanism; Distributed – a device that does not support the Plug and Play mechanism; LPC DMA – a device connected via LPC-bus.

Direct Memory Access. Part I

Direct Memory Access (DMA) is a mechanism of data exchange between an internal device and memory without engaging a processor. Such mechanism allows significantly decreasing the load on the processor and increasing a general productivity of a system.

The use of direct memory access is provided via a special DMA-controller which has got eight channels for simultaneous transmission of information on 8- or 16-bit buses.

The peak bandwidth via DMA-channels is about 2 MB/s, so the mains consumers of DMA-channels are audio cards, floppy-drives and old CD-ROMs. In old computers, DMA-controller also controlled the operation of hard disks but in modern systems this function is realized via a mechanism of the programmable input/output.

If it is necessary to exchange data fast, a processor takes over the control of the process of information transferring because the speed exceeds the capacities of DMA.

In case of manual allocation of DMA resources, it should be considered that, in contrast to allocation of interruptions, only one device should be reserved on one channel of direct memory access. The shared connection of several devices on the same channel is also possible, but remember that such connection may lead to some conflicts with the shared operation of these devices.

Manual Assignment of Interruptions. Part II

An amount of interruptions accessible for assignment depends on devices connected to a system. For example, if the support of a mouse is disabled in BIOS (the parameter “Mouse support”) an interruption IRQ12 will be accessible.

 To assign interruptions, you may also use the parameter “Slot n IRQ”, where n – a number of PCI-slot. This parameter enables to assign a particular interruption to a slot. The numbers of the appropriate hardware interruptions are used as the values of this parameter: IRQ3, IRQ4, IRQ5, IRQ7, IRQ9, IRQ10, IRQ11. Besides, you can use the value “Auto” that enables to set an interruption number automatically. It should be stated that this parameter cannot be used in Windows 2000/XP.

Another parameter for assignment of interruptions is “PIRQ_n Use IRQ”, where n – ranges from 0 to 3. This parameter also enables to assign interruptions individually to each device on PCI and ISA-buses. In contrast to the parameter “Slot n IRQ”, this parameter has a wide range of functional possibilities. Its values indicate free or accessible IRQ-numbers. There is also the value “Auto” that enables to perform autoconfiguration of devices.

The last parameter for assignment of interruptions is “PCI Device Search Order” that enables to change the sequence of PCI-slots. This parameter may have two values: First-Last – from the first to the last (a standard bypass); Last-First – from the last to the first (a reverse bypass).

Manual Assignment of Interruptions. Part I

Similar to the assignment of a separate interruption to video card, it is possible to assign a separate interruption to USB-bus in BIOS. To do this, use the parameter “Assign IRQ for USB” which has got two values: Enabled and Disabled. This parameter should be turned on if you use two or more USB-devices simultaneously, for example mouse and scanner. Turn this parameter off if there are no USB-devices or you use only one device, for example only scanner or only digital camera.

The other opportunity to get the additional free interruption is to switch off a floppy-drive. The parameter “FDD IRQ Can Be Free” (Report No FDD For Win 95) enables to free up an interruption IRQ6. This parameter has got two values: Enabled and Disabled. But if a floppy drive is connected to a system, you must switch off its controller for freeing up an interruption. To do this, set a value “Disabled” for the parameter “Onboard FDC Controller” (FDC Function) in a section “Integrated Peripherals”.

Use the parameter “IRQ n Assigned to” (IRQn) for manual assignment of the rest resources the hardware interruptions, where n – a number of interruption. This parameter may have values describing the type of device for which this interruption can be assigned.

  • Legacy ISA (ISA/EISA) – an interruption for ISA-devices that do not support Plug and Play technology. The interruptions for such devices are assigned in accordance with Technical documentation;
  • PCI/ISA PnP (PCI/PnP) – an interruption for PCI or ISA-devices that support Plug and Play technology.