Problem with battery and the real-time clock of Amstrad 1640

[tonata]

Hi,

I am using 2 x 3V coin batteries to replace the 4 x 1.5V for the real time click of my Amstrad 1640. It seems like the 6V reach the motherboard, but still it does not keep the date after complete power off. I also use a fuse and a diode (to block incoming tension from the motherboard and to reduce voltage), but I do not think these are the source of the problem.

There is Non-Volatile RAM (NVR): https://www.seasip.info/AmstradXT/16.../section1.html

Do I need a specific "date" program provided by Amstrad to set the date permanently?
The battery is not used while the system is on, which means the computer must switch quickly to the battery once powered off. Maybe this does not work or it happens too slow?

 

[modem7]

Do I need a specific "date" program provided by Amstrad to set the date permanently?

First, I know nothing of Amstrad computers.

The Amstrad PC1640 technical manual is at [here]. The '1.9 Real Time Clock' section of that informs us that:
* If the batteries are low or improperly connected, 'Please fit new batteries' will be displayed.
* The RTC chip is a "HD146818".
* The HD146818 sits at the I/O address of 70h and 71h.

So the Amstrad PC1640 is using the same RTC chip as the IBM AT (IBM 5170) and has that chip using the same I/O addresses as the IBM AT.

That explains why the web page at [here] says, "You can, however, easily restore the date and time should the battery be removed or become empty, using the DATE command in DOS." DOS version 3 (released with the IBM AT) or later will be required.

The PC1640 technical manual also indicates that the PC1640 stores different information in HD146818's RAM compared to what the IBM AT does. So SETUP programs for the AT are not applicable. The technical manual indicates that in a bad battery situation, the PC1640's POST automatically sets the configuration information stored in the HD146818's RAM to default values.

That all suggests to me that as soon as good batteries (adequate voltage, and connected in the correct polarity) are fitted, the "Please fit new batteries" message will disappear, and the user then uses the DATE and TIME commands in DOS 3 (or later) to set the correct date/time.

Maybe someone who knows for sure will post.

Regarding the diode that you have added. That is only required if the PC1640 uses rechargeable batteries. Does the PC1640 use rechargeable batteries?

 

[cwathen]

Always pleased to see another Amstrad PC user on here. I have a PC1512HD20 (with the 640KB upgrade). Even though I also own an IBM 5150, the Amstrad is still my go to XT-class computer. They are brilliant machines.

I am using 2 x 3V coin batteries to replace the 4 x 1.5V for the real time click of my Amstrad 1640. It seems like the 6V reach the motherboard, but still it does not keep the date after complete power off. I also use a fuse and a diode (to block incoming tension from the motherboard and to reduce voltage), but I do not think these are the source of the problem.

Why are you doing this vs just running it as designed? They are just normal AA batteries that fit into the compartment and your battery compartment looks fine to me! It was a very good solution in it's day and it's still fine now. Possibly it's to do with the current/power requirements of the circuitry. You can easily get 2500mAH out of good AAs vs just under a tenth of that out of CR2032s. The hardware may not work with coin cells even if you have provided the correct voltage.

Do I need a specific "date" program provided by Amstrad to set the date permanently?
The battery is not used while the system is on, which means the computer must switch quickly to the battery once powered off. Maybe this does not work or it happens too slow?

You don't need a special program to set the date & time, these machines do have a pretty good RTC implementation, The built in DOS date/time commands will pass the settings through to the RTC circuitry and similarly at boot DOS can pick up the date & time directly from the RTC without needing any special driver to be loaded.

However, the NVR feature was a lot more than just an RTC; there are various other system settings which can be stored in it similar to a CMOS setup program on a newer computer. You do need Amstrad's proprietary NVR.EXE utility to make use of this which came only on the specific copy of MS-DOS 3.2 that was bundled. Should you not have the original disk set you can either pay stupid money for them on eBay or just download them from here:

http://www.freetimeweb.nl/home/compu...wson/files.htm

Regarding the diode that you have added. That is only required if the PC1640 uses rechargeable batteries. Does the PC1640 use rechargeable batteries?

Nope, no charging circuitry. The batteries are designed to be readily replaced once they run flat which is why they are easily accessible (although a decent set of alkalines will last several years).