HP-48G clock mystery

[LowTech]

Hi,
I recently bought my first HP-48G on eBay. It's showing some strange behavior. The clock only runs when it is switched on. You set the time correctly and then switch the calculator off. Later after powering on again, the HP-48G shows the time it was switched off. And continues counting from there.

This of course also means that the alarm function is actually not usable either.

What could be the reason and can it be fixed?

[TomC]

Are the data and programs retained after power-cycling?

TomC

[LowTech]

Yes, everything is preserved.

[LowTech]

No idea if it's important, but the calculator showed a warning about invalid card data after power on. PINIT fixed this issue.

[TomC]

Is this a 48G or a 48GX?

[LowTech]

Yes, the warning message was strange, but it's a HP-48G!

[Kiwi]

When you have a HP48G with an 'Invalid Card Data' warning, there's a big chance that you have a modified (or upgraded) HP48G.
Check the available memory. Normally, HP48G's have 32KB of free mem, yours probably has 128KB of RAM. You can also check if Port 1 and up are available.
Companies that did this modification, also proposed 'speed' upgrades. You can check if a speed module has been installed by turning the calculator OFF, then press and hold the ON-key for 2 seconds and turn the calculator back on. The cursor is now blinking twice as fast. To set it back to normal mode do the same by pressing the ON-key for 1 second.
A side effect of the speed upgrade module is that it also alters the clock. So maybe your HP48G has been hardware modified.

[LowTech]

Thanks @Kiwi you nailed it down, this HP was modified.
Pressing the ON key a little longer, there is a soft beep and it runs with double speed.

But I'm unsure how to read the RAM configuration.

Mem available shows 256121 and
0 PVARS 258676.5
1 PVARS "SYSRAM"
2 PVARS 131072
3 PVARS 131072
4 PVARS 131072
5 PVARS 131072
>=6 PVARS Error: Port not available

Is it 256k RAM, or even more?

[Kiwi]

In your case, port 1 (128KB) has been merged with the built-in RAM (128KB), which gives you 256KB of RAM. You can create port 1 again with the FREE1 command.
On the hardware side, they probably replaced the 32KB built-in RAM with a 128KB module, added a 128KB RAM module to create port 1 and a 512KB module for port 2 -> 5.

[LowTech]

Thanks, that makes sense.
Show all 'speed' upgrades my clock issue (running only while powered on)?

[Kiwi]

I think all 'speed' upgraded HP48's involve a clock issue.
There's also some reference to it in the topic 'Some bad things' on this site.