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Thread: NuXT - MicroATX Turbo XT Motherboard - 9.55MHz, UMBs, XT-CF, SVGA, HD Floppy, Serial

  1. #1

    Wink NuXT - MicroATX Turbo XT Motherboard - 9.55MHz, UMBs, XT-CF, SVGA, HD Floppy, Serial

    Not sure whether this should go here or in marketplace, as it's sort of a show n tell n sell.

    Here's the result of a project I've been working on for a few months.

    Shout out to Sergey Kiselev for his schematics which I've used in a few functional blocks on this board, such as his Micro 8088 SBC.

    80's is coming back with the NuXT!
    MicroATX sized Turbo XT motherboard.

    Can be used as a full featured XT without any cards.
    Could add Sound, Network Card, or more storage/connectivity.

    Features:
    • 8088 and NEC V20 support
    • 8087 co-processor support
    • 4.77MHz, switchable to 9.55MHz with hotkey
    • 2x64K ROM, switchable with DIP switch, writable
    • 800K SRAM
    • - 640K conventional
    • - up to 160K UMBs (128K max when using EGA/VGA)
    • - Configured DOS 6.22 uses only 10K conventional!
    • Highly-compatible SVGA, up to 512K VRAM
    • HD Floppy controller, with FM support
    • Bootable CF Card Interface
    • Option ROM Socket, supporting 8K and 32K ROMs, writable
    • 16C550 Serial Port
    • PS/2 Keyboard Port
    • ATX Power Input. Generates own -5V
    • 4 x 8-bit ISA Slots
    • Front-panel connector for modern cases
    • Highly configurable with DIP switches. Can disable onboard peripherals.


    Now I just need to find a place that cuts out I/O shields in low quantities... I can get blank ones.
    I think they provide a professional finishing touch.

    Click the images for higher res.






    *Ugly rear bodge wire only on my prototype

    Monotech PCs - brand new Vintage computer parts and accessories - Click here!
    EternalCRT: MDA/CGA/EGA>VGA Converter, XT-IDE, XT-CF-Mini, AdLib, DeluxeFloppy, PS/2>XT Keyboard Converter, XT-SVGA, NuXT, XT-MegaIO

  2. #2

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    Haha, awesome. Is it just the one unit, or are you planning to make more?
    Computers: Amiga 1200, DEC VAXStation 4000/60, DEC MicroPDP-11/73
    Synthesizers: Roland JX-10/SH-09/MT-32/D-50, Yamaha DX7-II/V50/TX7/TG33/FB-01, Korg MS-20 Mini/ARP Odyssey/DW-8000/X5DR, Ensoniq SQ-80, E-mu Proteus/2, Moog Satellite, Oberheim SEM
    "'Legacy code' often differs from its suggested alternative by actually working and scaling." - Bjarne Stroustrup

  3. #3

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    I have made two. One is my bodge prototype seen here, and the other is for someone who bought one. They are in my little vintage PC parts shop in my signature.

    I have enough parts to make 3 more. If they prove popular, I'll source more parts.
    Monotech PCs - brand new Vintage computer parts and accessories - Click here!
    EternalCRT: MDA/CGA/EGA>VGA Converter, XT-IDE, XT-CF-Mini, AdLib, DeluxeFloppy, PS/2>XT Keyboard Converter, XT-SVGA, NuXT, XT-MegaIO

  4. #4

    Default

    Any chance a PS/2 mouse port can be wedged in? They did exist on the XT class PS/2 Model 25 and 30 although BIOS support might be an issue.

  5. #5

    Default

    Quote Originally Posted by njroadfan View Post
    Any chance a PS/2 mouse port can be wedged in? They did exist on the XT class PS/2 Model 25 and 30 although BIOS support might be an issue.
    The XT chipset has XT keyboard interface built in. I'm using an AT2XT microcontroller here. This is based on Sergey's Micro8088.
    Sergey's Xi8088 is an older design, that uses a full XT chipset instead of a single chip. This allowed using a PS/2 KB+M controller from Pentium systems. He also had more IRQs on the Xi8088 like an AT.

    I only have the 8 IRQs.
    There is one way I can add PS/2 mouse support. I need all of the following:

    Stacked mini-DIN 6 connector
    Figure out 16C552 instead of 16C550
    PS/2 to Serial mouse microcontroller
    We'll only have IRQ 2, 5, and 7 left.
    The 16C552 has parallel port too. I can add that if I can find a raised DB25F connector. Then only IRQ 2 and 5 is left for sound cards etc.

    I do plan on sorting out a PS/2>Serial mouse converter box some time. With the option of coming with a new Microsoft Optical Mouse that supports PS/2 mode (can still get them).

    Cheers
    JD

  6. #6
    Join Date
    Jan 2010
    Location
    Central VA
    Posts
    4,380

    Default

    Excellent! If it's based on Sergey's work, you'll be releasing the design files in accordance with the GNU GPL v3, correct?

  7. #7

    Default

    Quote Originally Posted by glitch View Post
    Excellent! If it's based on Sergey's work, you'll be releasing the design files in accordance with the GNU GPL v3, correct?
    Of course!
    I'll clean up my project folder and chuck it up on GitHub soon.

  8. #8
    Join Date
    Feb 2017
    Location
    Chilliwack, BC, Canada
    Posts
    216

    Default

    Nice!

    $400 CDN is a bit out of my budget range for a toy (looking to get a 3D printer sometime soon). But it's comparable, if not less than what a fully loaded XT can go for, and you can slap this together with any random ATX chassis/PSU you happen to have lying around (we've all got those)!

    Any chance of getting this as a bare board or kit format at a reduced price? Building it is half the fun anyways.
    My vintage systems: Tandy 1000 HX, Tandy 1000 RSX, and some random Pentium in a Hewitt Rand chassis...

    Some people keep a classic car in their garage. Some people keep vintage computers. The latter hobby is cheaper, usually takes less space, and is less likely to lead to a fatal accident.

  9. #9

    Default

    Quote Originally Posted by blackepyon View Post
    Nice!

    $400 CDN is a bit out of my budget range for a toy (looking to get a 3D printer sometime soon). But it's comparable, if not less than what a fully loaded XT can go for, and you can slap this together with any random ATX chassis/PSU you happen to have lying around (we've all got those)!

    Any chance of getting this as a bare board or kit format at a reduced price? Building it is half the fun anyways.
    I can offer bare boards for $20 + postage.
    I can offer a kit for full price minus $40.

    I don't think I'll offer kits yet, as I have no way of testing the Trident SVGA chips, and don't want to send untested vintage chips. I am working on making up a QFP-160 socket board for testing them.
    Monotech PCs - brand new Vintage computer parts and accessories - Click here!
    EternalCRT: MDA/CGA/EGA>VGA Converter, XT-IDE, XT-CF-Mini, AdLib, DeluxeFloppy, PS/2>XT Keyboard Converter, XT-SVGA, NuXT, XT-MegaIO

  10. #10

    Default

    nztdm: FYI, that the Ad Lib clone card you're selling is based on my open source clone design which is licensed under CC BY 4.0 (Creative Commons Attribution 4.0 International). According to the terms of the license you need to give appropriate credit, provide a link to the license, and indicate what changes you made, if any. I'd appreciate it if you followed those terms by adding that information to your website and your eBay auctions. Thanks!

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