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Thread: RTC ISA 8 bits (Very Low Profile)

  1. #1

    Default RTC ISA 8 bits (Very Low Profile)

    I share a variant of the SMBacker RTC design:



    Gerbers availables on OSHPark

    This design consists of a very low profile ISA card, which has the port 70h mapped as fixed. Soon Sergey's Micro8088 project will have support for it.

  2. #2

    Default

    Now I offer this product through Tindie for whom you may be interested, kit or fully assembled:

    https://www.tindie.com/products/spar...y-low-profile/

    I have modified the micro8088 BIOS to make it compatible with it (version 0.9.7), and Sergey has optimized and improved the code. Until he decides to make it public in your GitHub repository, I leave it available in mine, as well as the instructions for its flashing:

    https://github.com/spark2k06/micro_8...ee/master/BIOS

    However, this board can be used on any other PC with an ISA port and appropriate management software.

  3. #3

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    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.
    Last edited by spark2k06; November 20th, 2019 at 01:56 AM.

  4. #4
    Join Date
    Jan 2012
    Location
    Raleigh, NC, USA
    Posts
    503

    Default

    Thanks for sharing this project!

    Heather

  5. #5

    Default

    Quote Originally Posted by spark2k06 View Post
    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?
    Current Wish List: 1. IBM 7531 Industrial Series PC 2. NEC MultiSync XL (JC-2001) Monitor 3. MicroSolutions MatchPoint AND/OR UniDOS card 4. Compaq 14" VGA CRT Monitor (the one that came with the SystemPro). 5. Stacker HW CoProcessor Board MCA BUS. If you have any of the above for sale please PM me. Thank you!

  6. #6

    Default

    Quote Originally Posted by Shadow Lord View Post
    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. 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:



    Edit:

    Okay, I see there are other ways to add RTC, in any case, mine would be one more.
    Last edited by spark2k06; November 27th, 2019 at 03:05 AM.

  7. #7

    Default

    Quote Originally Posted by spark2k06 View Post
    The machine to which it is intended is an XT, and I think that not everyone has RTC unlike AT.

    ...

    Okay, I see there are other ways to add RTC, in any case, mine would be one more.
    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.
    Current Wish List: 1. IBM 7531 Industrial Series PC 2. NEC MultiSync XL (JC-2001) Monitor 3. MicroSolutions MatchPoint AND/OR UniDOS card 4. Compaq 14" VGA CRT Monitor (the one that came with the SystemPro). 5. Stacker HW CoProcessor Board MCA BUS. If you have any of the above for sale please PM me. Thank you!

  8. #8

    Default

    Now available in Tindie, soon will publish the gerbers, the Kicad project and the SPLD files.

    https://www.tindie.com/products/spar...-profile-spld/

    Quote Originally Posted by spark2k06 View Post
    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.

  9. #9
    Join Date
    Mar 2017
    Location
    New Jersey, USA
    Posts
    546

    Default

    Quote Originally Posted by Shadow Lord View Post
    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.
    here's an example from back then of a CPU interposer design with a battery holder:
    https://books.google.com/books?id=iS...PA38#v=onepage

    and here's an example of the floppy interposer version:
    https://books.google.com/books?id=k3...PA78#v=onepage

  10. #10

    Default

    They are very pretty, but are they sold today? Where and for how much? Are they configured on the standard port 70h?

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