Are there other ports to read CMOS

[Tamas]

I would similar to write a program that determines to among additional make sure a number of locations in systems "CMOS" memory (RTC-CMOS). How is the most excellent method to do this. I have read on a number of places that it has something to do by means of ports 70hand 71h. Are they obtainable in OS/2 or is there a superior method. Certain information in sequence on status of ThinkPad Buttons is situated there, and I would similar to have some indication of their status. So I immediately necessitate reading the memory not to write it.

[Filiberto]

The "CMOS" is a tiny bit of extremely low power tranquil memory that lives on the similar chip as the Real-Time Clock. It is moderately convenient to essentially imagine of the RTC as being "part" of CMOS. CMOS (and the Real-Time Clock) be able to merely be accessed from side to side IO Ports 0x70 and 0x71. The function of the CMOS memory is to accumulate 50 (or 114) bytes of "Setup" information in sequence for the BIOS at the same time as the system is turned off for the reason that there is a separate battery that maintain the Clock and the CMOS information active.

[Aandaleeb]

CMOS values are have right of entry a byte at a time, and every byte is independently addressable. Every CMOS address is conventionally called a "register". The first 14 CMOS registers have right of entry and control the Real-Time Clock. In fact, the merely truly helpful registers remaining in CMOS are the Real-Time Clock registers, and register 0x10. The entire additional registers in CMOS are approximately completely obsolete (or are not standardized), and are therefore useless.

[mathews]

For prudence in the olden days, numerous functions were amalgamated together on chips where there was "room" tranquil if they did not belong mutually. An illustration is putting the A20 address facilitates on the PS2 keyboard controller. In the similar method, the "NMI disable" control was put together by means of the CMOS controller and the Real-Time Clock. NMI is predestined to communicate a "panic" status from the hardware to the CPU in a technique that the CPU not be able to ignore. It is characteristically used to signal memory errors. For additional information in sequence regarding NMI, observe the NMI article.

[Wampanoag]

Accessing CMOS is tremendously simple, additional than you always necessitate taking into account how you desire to handle NMI. You "select" a CMOS register (for reading or writing) by sending the register numeral to IO Port 0x70. In view of the fact that the 0x80 bit of Port 0x70 controls NMI, you constantly end up setting that, too. So your CMOS controller forever requirements to be familiar with whether your OS requirements NMI to be enabled or not.

[RoninBlade]

The appropriate functioning of the BIOS throughout bootup depends on the values in CMOS. So the values are prevented against random changes by means of checksums. It is extremely unwise ever to write a assessment into several of the CMOS registers (except for the RTC) for the reason that when you revolutionize a value you in addition have encompassed to go fix a BIOS-specific checksum in a dissimilar register or else the next boot determine to crash by means of an "invalid checksum" error. And in view of the fact that the checksum is situated at a proprietary BIOS-specific register number, good luck finding it.

[Milton.J]

This register includes the merely CMOS value that an OS might ever locate to be helpful. It describes the "type" of every of the two floppy drives that might be attached to the system. The high nibble describes the "master" floppy drive on the most important bus, and the low nibble has an indistinguishable explanation for the "slave" floppy drive.

[Techguru01]

There are more than a few CMOS registers that are consistent, and that seem to report helpful information in sequence regarding the total memory on the system. On the other hand, every of them is lacking vital information in sequence that you are OS determine to necessitate. It is always superior to utilize a BIOS function call to get information in sequence regarding memory than to utilize the information in CMOS and you have to observe Detecting Memory (x86).