Forum Rules and Etiquette

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This forum is part of our mission to promote the preservation of vintage computers through education and outreach. (In real life we also run events and have a museum.) We encourage you to join us, participate, share your knowledge, and enjoy.

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This forum has a private message feature that we want people to use for messages that are not of general interest to other members.

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Rule 5: Copyright and other legal issues

We are here to discuss vintage computing, so discussing software, books, and other intellectual property that is on-topic is fine. We don't want people using these forums to discuss or enable copyright violations or other things that are against the law; whether you agree with the law or not is irrelevant. Do not use our resources for something that is legally or morally questionable.

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New user moderation

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Upgrading IBM 5162 XT/286 to 8 MHz

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    Upgrading IBM 5162 XT/286 to 8 MHz

    Based on research here in the forum, I upgraded my IBM 5162 XT/286 to 8 MHz as follows:

    1. crystal Y1: 12 MHz to 16 MHz
    2. BIOS: AMI 1989 / WINBOND W27E257-12
    3. RAM 0-512: 15ns to 10 ns
    4. RAM 512-640: switched off, as I don't have 10 ns chips; but it will be upgraded.
    5. NPU: not yet installed

    I only switched ON the converted 5162 for max. 1 minute and tested it with CHECKIT: The frequency changed from 6 to 8 MHz without further action.

    Now my question: Are further adjustments necessary for continuous operation?

    Of course, I forgot to mention that I also use a different CPU: 80286-6 to 80286-8.


      Typically the 6MHz AT boards overclock to 8MHz without much of a fuss, even if you don't change anything.
      If you want to play it safe, you can also replace the 82284 clock generator, and 82288 bus controller (the ones installed may already be rated for 8MHz though).

      I have also overclocked my XT-286 board, but I have mine running at 10MHz and it seems to handle it pretty well. I replaced the same parts you did, as well as the 82284 and 82288. I also tested at 12MHz, and it seemed to handle it a lot better than the 5170 AT boards I tried...though the AT bus will run at 12MHz, so you need to make sure you expansion cards are up to the job.
      "Will the Highways on the internets become more few?"

      V'Ger XT


        In my XT/286 the clock generator Siemens SAB 82284P is installed at U79. According to the Siemens manual the SAB 82284P generates a system clock up-to 16 MHz for SAB 80286 Processors.
        Last edited by haglebu; December 22, 2020, 07:43 AM.


          The bus controller at U68 is an Intel D82288-8. This should therefore be 8MHz. In the following picture you can still see the „old“ crystal with 12 MHz!



            Is changing the BIOS required? Does it have the same software speed limitation as the AT?


              I had installed the AMI BIOS anyway because I find the in-built SETUP simply better. After replacing the 12to16 MHz crystal, I did not make any other settings.


                Originally posted by haglebu View Post
                3. RAM 0-512: 15ns to 10 ns
                4. RAM 512-640: switched off, as I don't have 10 ns chips; but it will be upgraded.
                Extremely minor nitpick: "-15" and "-10" on this vintage of DRAM chip means "150 ns" and "100 ns" respectively, not 15/10.
                My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot


                  How embarrassing! Yes, you are right. My fault!

                  Last edited by haglebu; December 22, 2020, 01:10 PM.


                    I don't think I've ever seen 100ns 41256 or 4464 chips... Are you sure you can't use 120ns ones though? Usually expansion boards with 120ns memory will work fine in 8MHz AT's... Although if not, would that be due to the fact that the 5162 is 0 wait state and the 5170 is 1 wait state?


                      Yes, in the range from 512KB to 640KB I have installed memory chips from NEC (D41464C-10), see picture.


                      Probably 120ns chips are also sufficient. According to „minuszerodegrees“ in the motherboard of the 5170 (Type 3, 8MHz), only 150ns RAMs are installed by default. But I didn't have 120ns RAM at hand, so I used 100ns.


                        Addition: According to the users manual of the AST Rampage 286, which was made for the IBM XT/286 and the IBM 5170:

                        „The RAM chips used with the Rampage 286 board must be 120-nanosecond access time or faster (such as 100-nanosecond).
                        User's manual, p. 1-3, 1986“