# Panasonic KX-TD816BX Hardware Insights
## ROM/RTC clock Board

{{:telephony:pqup10092zb.png|}}

This complex seems to be upgradeable (if you ever find that stuff.) Here we can find: 

- IC20: **P401A**, matches the system ROM version (*P401A*60905A), so it's probably the main firmware; 
- IC21: **P402A**, Google returns nothing useful, unknown ROM chip; 
- IC24: **CXK581000AP-10LL**, or _131072-word × 8-bit High Speed CMOS Static RAM_, which seems to provide our system with healthy 128 KB; 
- IC25: **idem**, bringing the **total amount of RAM in this module to 256 KB**; 
- IC26: **OKI M6242B**, an RTC clock chip; 
- X2: **32.768 kHz crystal oscillator** for the RTC chip; 
- BAT: **CR2354 battery**, 3V, probaly of the /1GUF variant. 

### Problems

- The RTC battery is probably long dead and showing signs of oxidation on it's legs; 
- There's was a bad and mysterious corrosion under the RTC oscillator, that I've already removed, after taking this photo; 
- This same oscillator isn't operating reliably, sometimes it takes a while for the clock to start, well, _clocking_, and this component is probably the culprit;