Compaq Presario CDS 520

In this post I will write some hopefully useful observations from working with the Compaq Presario CDS 520, with the goal of turning it into a MS DOS gaming machine, similar to my Presario 433 I owned as a child.

(This post is updated on a regular basis).

Compaq Presario CDS 520 specifications

  • Year: 1994
  • 486 SX 66 MHz
  • 4 mb ram (+ 4 mb expansion = 8 mb)
  • Cirrus Logic graphics adapter
  • ESS 688 onboard sound
  • ~500 mb hdd
  • 3.5¨ 1.44 mb floppy
  • CD-rom
  • MS DOS 6 + Windows 3.1 default

General remarks

  • BIOS: As explained by, these machines does not come with a vast range of configuration options in their BIOS. They autodetect your disks, and can boot from floppy and hdd. Larger drives than 504 mb can be used, although the limit is unclear (2.5 gb confirmed ok). To access BIOS, press F10 when the white rectangle is flashing to the right top of the screen during boot-up. If this fails, you do not have a setup partition on your computer. Then, you need to boot up from a floppy disk to access the bios. To prepare a floppy you need to download the SP1363.exe SoftPaq (see above, I will also provide links here shortly) and make a disk out of it. If you are making a clean install of DOS, you can also use this disk to make a setup partition on the hdd.
  • Integrated builds. One limitation with these all-in-one machines is of course that if something fails, the whole machine might be rendered useless. They also have limited room for additional cards and other upgrades. That is essentially the cost of the compact form factor. My Compaq Presario 433 did not have an integrated CD-rom for example. Due to the slow LPT-port, the performance of parallel port CD-roms were limited, so I used long IDE- and Y-power cables and simply positioned the CD-rom outside of the machine. The advantage with the CDS520 is that it comes with an integrated CD, which is really beneficial when installing games etc. I still keep a lot of CDr’s at home for my Dreamcast, and other consoles.

Installing a Soundblaster 16

My biggest problem with this machine is the ESS688 onboard sound. Although it is soundblaster compatible in games, the sound volume tends to be to loud, and the front volume control does not do a great job adjusting it (neither did the software mixer). So, what I wanted to do first, was to install a faithful soundblaster 16 ISA card while still being able to utilize the internal speakers, and being able to accurately control the volume.

I found a soundblaster 16 CT2960 card on Austrian eBay for a good price. Although reading negative remarks about the VIBRA16-series I am perfectly fine with its performance. To use the internal speakers with this card, I connected them to the 3.5 mm out jack of the soundblaster, with a volume control on the audio cable coming out from the back of the computer. It works very well! Only problem is that the right speaker also served as the internal PC speaker. I solved this by simply using a speaker from a broken Nintendo Gameboy as PC speaker. This speaker had a most pleasant tone to it than the original. So, now I can enjoy games at a pleasant and adjustable volume, with full soundblaster compability. The installation is fully reversable and no harm was done to the machine.

Compaq Presario CDS 520 Sound

Compaq Presario Sound

The VIBRA16 driver installation was done by using the Sound Blaster 16 Value PnP (Vibra16) CD from Since the card is Plug n Play, it installs a TSR program, followed by additional configurations, such as the set blaster environment. Although these take up some memory it was not that bad (616kb of conventional memory left at the moment), they can probably be optimized later (I removed the content the installation added to config.sys).

Coming steps: cpu, memory, storage and network upgrades

The machine could benefit from installing a 486 DX2 66 MHz CPU, and some additional RAM. I also have a 3COM ISA Ethernet card for Internet connectivity, which I would do through Windows 3.11. The current Windows-installation from the former owner contains some interesting programs which I am not prepared to replace with a clean install just yet. Also, sooner or later, I will have to replace the hard drive with something larger, and then, an IDE to compact flash adapter might come in handy. Although, I would miss the sound of the spinning hard drive!

Another option would of course be Windows 95, but for a MS-dos gaming machine I really don’t see the purpose at the moment. Perhaps I will prepare one such solution on a dedicated CF-card in the future.


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