5 ms·

So is the RTC battery still a problem in modern computers?

kalleboo 4y ago
Yes, but modern computers tend to use CR2032 batteries that are less prone to leaking. Or they're laptops which have their own battery issues (swelling and fire)
amelius 4y ago
I've noticed that some motherboards power the clock through mains power even when turned off.
- exmadscientist 4y ago
  This is desirable because the mains frequency is much more accurate, long-term, than the crystal frequency. So the very best designs use a design which is mains powered as much as possible, even using a rechargeable lithium coin cell that is slowly recharged whenever mains is available, but then switch over to the crystal when no mains is available.
  - charles_kaw 4y ago
    accuracy isnt really important anymore for consumer gear - as long as it's accurate enough to have the month right over a few years of inactivity, it'll pass the certificate checks required to do ntp over ssl - which most modern systems do by default
    - exmadscientist 4y ago
      That's only applicable for systems with a network connection. Many things still don't and shouldn't.
      - charles_kaw 4y ago
        We are talking about modern computers. Not embedded devices. That is a whole separate category :)
  - johnwalkr 4y ago
    This sounds good for simplicity when AC power is almost always available - it would be interesting to see what the best solution is for each use case. The time synchronization from AC can drift by a second or more over one day, but it is controlled very well over longer time periods. So if you’re switching back and forth between it and quartz, especially at regular intervals error could somehow accumulate. An interesting thing is emergency power supplies don’t always precisely control this, so after a disaster sometimes all AC connected clocks in an area drift by the same number of minutes. NTP or radio synchronization is probably better in many cases since those are absolute rather than relative references. And GPS should normally be the best although there are cases where 1, 2 or all 3 of those might be unavailable.
- johnwalkr 4y ago
  Wouldn’t this require a specialized PSU to pass along the 50 or 60Hz AC frequency in some way?

Yes, but modern computers tend to use CR2032 batteries that are less prone to leaking. Or they're laptops which have their own battery issues (swelling and fire)

amelius 4y ago

I've noticed that some motherboards power the clock through mains power even when turned off.

exmadscientist 4y ago
This is desirable because the mains frequency is much more accurate, long-term, than the crystal frequency. So the very best designs use a design which is mains powered as much as possible, even using a rechargeable lithium coin cell that is slowly recharged whenever mains is available, but then switch over to the crystal when no mains is available.
- charles_kaw 4y ago
  accuracy isnt really important anymore for consumer gear - as long as it's accurate enough to have the month right over a few years of inactivity, it'll pass the certificate checks required to do ntp over ssl - which most modern systems do by default
  - exmadscientist 4y ago
    That's only applicable for systems with a network connection. Many things still don't and shouldn't.
    - charles_kaw 4y ago
      We are talking about modern computers. Not embedded devices. That is a whole separate category :)
- johnwalkr 4y ago
  This sounds good for simplicity when AC power is almost always available - it would be interesting to see what the best solution is for each use case. The time synchronization from AC can drift by a second or more over one day, but it is controlled very well over longer time periods. So if you’re switching back and forth between it and quartz, especially at regular intervals error could somehow accumulate. An interesting thing is emergency power supplies don’t always precisely control this, so after a disaster sometimes all AC connected clocks in an area drift by the same number of minutes. NTP or radio synchronization is probably better in many cases since those are absolute rather than relative references. And GPS should normally be the best although there are cases where 1, 2 or all 3 of those might be unavailable.
johnwalkr 4y ago
Wouldn’t this require a specialized PSU to pass along the 50 or 60Hz AC frequency in some way?