My Vintage Computer Virtual Museum and blog page.

Compaq CDTV520

My Compaq CDTV 520 (added to my collection in 1998)

This PC quit POSTing, I have no clue what the issue is, it does not seem to run any code on power up from what I can tell with my diagnostic tools.  Many parts have been stripped to use elsewhere until I can repair it.

  • 5x86GP-100 (Cyrix 486 upgrade chip in Trinity Works socket adapter)
  • 64MB RAM
  • 4GB HD
  • 3com Etherlink III
  • Adaptec AVA-1515 SCSI card (for external Zip or Jaz drives)
  • CD-ROM
  • Windows NT4

Originally this PC shipped with an NTSC TV Tuner, however it has no driver support in later versions of Windows, and NTSC broadcast is dead, so I removed it in favor of a SCSI card.


  1. whoknows says:

    We had this exact model, and we got the evergreen upgrade. Worked like a charm until software publishers started demanding higher spec systems.

    • I had an Evergreen CPU in this for a while, but sadly it died (it overheated), so I got the Cyrix 5×86 instead. This is still a great machine for period software, but you are right, it will not run modern software.

  2. Eric Bert says:


    I surfed arround on you website and I loved it. Mostly because I collect computers too 😉 So, I have a question about this computer : why to choose a Cyrix Cpu? I ask this because in the end of 98 I got a Pentium 133 in the need of more power. So I got a Cyrix pr 150 in exchange to put on in my computer. This CPU lasted in my computer because it was slower in games than my 133. So, I sell it to got a Pentium 166mmx and oced it to 180mhz. I remember how my computer mentor in these days questionning why I decided to put a Cyrix in my computer. I answered, because in Quebec, the winter is cold and my computer is now able to produce some heat 😉 It’s my story about the only Cyrix I had in a computer. I have some Cyrix/Via cpu’s in my collection.

    • I chose the Cyrix in this case because it is one of the better performing 486 class CPUs (mainly due to the larger cache and branch prediction), they lost their edge in the Pentium era, Intel and AMD shot far ahead of them, and Cyrix was pretty much relegated to low cost low performance market after that.

      This 100mhz 486 class CPU performs on par with a Pentium 75, I don’t think even Intel’s own “486 upgrade”, the Pentium Overdrive chips (which do not fit a standard 486 socket, only special “overdrive” capable sockets, I have one, but it doesn’t fit this board) perform as well, I know it performed pretty close on most tests to AMD’s 133mhz offering. So for this generation of PC it is one of the better choices.

  3. Joao Cunha says:


    I’m also an happy owner of a CDS 520 for 25 years 🙂 .
    I just manage to buy an Evergreen 5×86 133mhz and it supports 16kb of l1 cache (configurable write-through/write-back), just like the cyrix 5x86GP-100 that you have.
    I always thought that this model would never support write-back l1 cache. But If you take a look at the mobo (near the battery) there is a missing jumper for switching between WB/WT cache, which leads me to think that the VLSI chipset being used actually supports WB cache but it was “disabled” due to the official supported cpu’s (sx2, dx2). Have you noticed and tested these missing jumpers?

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