I still have to check the connections and routing before ordering PCBs but I think that this way everything is much cleaner in a similar space. Both the DS12885 and the ATF16V8B will go in socket, and although I have the SPLD code ready for it to work on the standard RTC 70h port, it could be programmed by anyone to work on another port.
Hi,
Nice work but I am not sure what need/problem you are addressing? What I mean is if you want to add in just an RTC and you want to have absolute minimum profile you would go with one of the under BIOS RTC boards. If you want to replace the Dallas RTC and provide CMOS then again there are PCBs that replace that chip directly. Only time I could see this being useful is if you have a soldered RTC/Dallas chip and you do not want to unsolder it.Then you could plug it into an ISA slot but you give up an ISA slot.... So what am I missing?
The machine to which it is intended is an XT, and I think that not everyone has RTC unlike AT.
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Okay, I see there are other ways to add RTC, in any case, mine would be one more.
New design removing discrete logic and replacing it with an SPLD:
I still have to check the connections and routing before ordering PCBs but I think that this way everything is much cleaner in a similar space. Both the DS12885 and the ATF16V8B will go in socket, and although I have the SPLD code ready for it to work on the standard RTC 70h port, it could be programmed by anyone to work on another port.
Once I have confirmed the correct working of the PCB, I will make the sources and gerbers public in my GitHub directory, apart from leaving them available for purchase both in kit and full assembled in my Tindie store.
Yes and they take far less space then this design. What is needed in the 5150/5160 class machines is a ROM (or CPU) interposer design that allows for a battery holder. Most of the "vintage/original" designs were with a self contained battery so are no good any more. However, there were some even back then that allowed for a battery....
Edit: The FDC interposer is a new one to me. Interesting idea although I'd be worried if it would cause problems with such things as XT-FDC, or Copy II PC Option boards.
Ahhhh, yes... Microsync dClock...here's an example from back then of a CPU interposer design with a battery holder:
https://books.google.com/books?id=iS8EAAAAMBAJ&ppis=_e&lpg=PA38&ots=7_Ba8fNJqA&pg=PA38#v=onepage
Yes and they take far less space then this design. What is needed in the 5150/5160 class machines is a ROM (or CPU) interposer design that allows for a battery holder. Most of the "vintage/original" designs were with a self contained battery so are no good any more.
The machine to which it is intended is an XT, and I think that not everyone has RTC unlike AT. In my case, and more specifically, I built it to use it on my Micro8088, to which I modified its BIOS to make use of it but it could be used in any XT through an application or by modifying its BIOS, in any case, using port 70h:
My generic RTC program supports the AT clock mapping in an XT, so it should work with your card.
http://www.minuszerodegrees.net/rtc/david_m/CLOCK.zip
A new version of the above utility translated into C language:
View attachment 60613
there is no functional changes.