Frequently Asked Questions

What happened to PC99?

The last versions of PC99 were PC99 Stage 6 Full and PC99 Stage 6 Light. PC99 Stage 6 Full is now called PC99 DOS. PC99 Stage 6 Light is discontinued and is no longer a supported product.

PC99 DOS is included with CaDD PC99 Suite. It requires DOSBox to run on Windows 7 and higher. There are some changes to cfg.exe to integrate PC99 DOS into the Suite environment.

For full information see: “PC99 DOS”

What happens to my copy of The Cyc?

If you own The Cyc, you are a registered owner of either PC99 Stage 6 Full or PC99 Stage 6 Light.

CaDD PC99 Suite contains a full copy of The Cyc and is almost certainly later than the version you have. When you have installed CaDD PC99 Suite, The Cyc can be found in \cadd\cyc. You are requested to destroy your current copy of The Cyc. The license you have does not allow The Cyc to be resold. The Suite version has many new files, and corrected files. Under no circumstances should you try to mix and match versions of The Cyc as this will break hyperlinks to any files that have been moved or renamed. Just rest assured that the Suite version of The Cyc is complete.

If you have no interest in CaDD PC99 Suite, but just want the latest copy of The Cyc, you can still order an update as before. The cost is $9.94 in the US, and $11.94 overseas. The price includes shipping and handling. Because The Cyc is now integrated in CaDD PC99 Suite, it will need to be “unbundled” for an upgrade, i.e., there will be no Suite files on the DVD. Please allow an extra three days for this process after CaDD receives your order.

What do I do with the supplied TI 5.25″ disk if ordered?

Optionally included with CaDD PC99 Suite is a TI 5.25″ DSSD disk. This disk contains the CaDD PC99 Suite transfer utilities written in TMS9900 Assembly Language that allow you to transfer binary images of TI disks between a TI-99/4A and a PC that are cabled together through the TI RS232 and PC COM or USB->COM ports. The cable is an off-the-shelf AT modem cable — not a null modem cable. [See the PC99 DOS documentation for pinouts.]

After installation of CaDD PC99 Suite, A binary image of the CaDD TI 5.25″ disk is stored in \cadd\dsk\pc99.dsk. It is a Windows file.

To transfer disks you run a 9900 Assembly Language program on the TI, which is loaded from the CaDD 5.25″ disk. You run the companion 9900 Assembly Language program on the PC, and it is loaded from pc99.dsk. The program executing on the PC is, of course, emulated by PC99W. It is not a PC executable.

If you no longer have a TI, then the CaDD-supplied 5.25″ TI disk serves no purpose. If you do not have a TI, or do not use this disk, PC99W will still operate correctly, and will not be affected in any way.

Final note: If you have a 5.25″ drive on your PC and try to read the TI 5.25″ disk in it, Windows will return:

General failure reading drive B
Abort, Retry, Fail?

The reason for this is that the TI 5.25″ disk is not a Windows formatted diskette. It is a TI formatted disk that can only be read by a TI disk controller (TI, Myarc, Guion, CorComp, BwG).

As an alternative, the utilities supplied on the 5.25″ TI disk, can be used to create a series of disk dump files. These files can be copied to a PC-formatted 5.25″ disk in a TI system using PC-Transfer. This disk can then be read in a PC 5.25″ drive. This is much more difficult to do than the direct-connect method, and you must have PC-Transfer, a third-party program which is not included with PC99.

Why can’t TI disks be read directly on the PC?

Our understanding is that we will not be able to do this reliably. The best we would be able to offer is a utility that will read a TI disk in a PC 5.25″ drive and convert it to PC99 format.

The following points are offered to support this argument:

  1. If the operation is unreliable, it becomes extremely difficult for us to support. We simply do not have the resources to deal with every PC and every PC 5.25″ drive combination that might occur.
  2. TI disks are 5.25″. Most of today’s PCs no longer have a 5.25″ drive.
  3. We understand that “recent” PCs with 5.25″ drives, have had a signal line removed which makes it impossible for them to read TI disks. “Vintage” PCs may or may not work, since the PC controller has difficulty reading sectors numbered 0-8 (TI method) rather than 1-9 (IBM method).
  4. We found a company in California that was able to read samples of TI disks we sent them. They were willing to sell us their library for $2,500 with the caveat that it was not guaranteed to work with all 5.25″ drives. The cost was prohibitive.

For these reasons no development is being done in this area. The PC99 product includes utilities that let you move your disk library to the PC. The easiest way to do this is to have a TI and PC connected together through their serial ports. The same utilities can also be used to create disk dumps which can be transferred to a stand-alone PC using PC-Transfer. PC-Transfer is a third-party product and is not included with PC99. This method requires having a 5.25″ drive on the PC — preferably 360K and not 1.2 Mb.

For people who no longer have access to a TI system, CaDD provides a disk conversion service.

CaDD has an open offer to any programmer: Write us a utility that will read a TI 5.25″ disk in a PC 5.25″ drive and we will include it with PC99. You can do this as shareware and we will include the shareware notice with PC99 if you desire. We can also include your utility in the PC99 Add-Ons sections on this web site.

Note: There is at least one published routine written in C that we have tried that does not work on our test systems. We have also tested a package developed by Gary Bowser that yields very poor results.

Update 20000727: Paolo Bagnaresi of Italy has released TI99-PC. The author claims this program will read TI 5.25″ disks in a PC drive. The file can be downloaded from Use an ftp client and log in as “anonymous”. Use your email address for a password. The file is in the /utils directory. This update is for information only. CaDD Electronics does not endorse or support this program. Any questions about it should be emailed to Update 20130830.Paolo Bagnaresi d. August 22, 2013. The email address is no longer valid.

What language is CaDD PC99 Suite written in?

  • PC99W.
    Pelles C for Windows.
  • PC99W Disk Utilities, and PC99W Config.
    Microsoft Visual Basic 6 under Visual Studio 6 Enterprise edition.
  • PC99 DOS, cfg.exe, and utilities.
    Watcom 11.0c, and wasm. The Read Sector and Write Sector utilities to transfer disks are TI programs and are written in TMS9900 Assembly Language.

Who are the CaDD PC99 Suite developers?

There are two developers: Eric Firestone, and Mike Wright.

  • Eric wrote the PC99W program and its debugger. PC99W is partially based on an early Windows version written by Mark van Coppenolle, which itself was based on PC99 DOS, which was mostly written by Greg Hill. Eric added considerable functionality to PC99W raising it to a level where it could be delivered as a product.
  • Mike conceived the project, writes the PC99 DOS utilities, writes PC99WDU and PC99WCFG, writes the documentation, writes The Cyc, maintains the CaDD web site, and is responsible for order handling.

CaDD would also like to thank the many people that helped in development. In alphabetical order: Michael Becker, Mickey Cendrowski, Dan Eicher, Larry Hoffman, Marc Hull, Klaus Lukaschek, Ernie Pergrem, Stephen Shaw, Lee Stewart, and members of the PC99W Beta Test Group on Yahoo.

Does PC99 DOS run under Linux?

PC99 DOS has been run under Linux using dosemu. Here is the how to instructions in pdf format provided by Dan Eicher.

CaDD had a machine running Fedora 13 and has successfully run PC99 under DOSBox. If you have a problem running under any version of Linux, first test PC99 DOS under its supported configurations on a DOS or Windows machine. If it works, then we are unable to support the Linux configuration. You should file a Bugzilla report with the maintainer of your Linux distro.

Most Linux distributions are open source, and may be freely disseminated. PC99 DOS is a proprietary product and may not be given away for free in any format. This includes bundling it with a Linux image. This approach is similar to products like Return to Castle Wolfenstein from Activision. RtCW is sold to run under Windows. It can also be run under Linux, but you have to own the original Activision RtCW CD to do so. You must copy proprietary files from the Activision CD to make RtCW run under Linux. The same concept applies to PC99 DOS. If you make a Linux distribution that will run PC99 DOS, it is your right to distribute this freely, minus the PC99 DOS files that CaDD delivers. If the target user is a registered PC99 owner, then your distribution can be used by that user, once the required proprietary files are copied from the CaDD PC99 Suite DVD delivery media. If you create such a distribution, you should supply clear documentation and/or a Linux shell script or program to retrieve the PC99 DOS files and place them in your tree.

If you have a website where such a distribution can be downloaded, please let CaDD know, and we will add a link to it if you desire. You should also offer an email address for support questions.

The following information was written by and provided to CaDD by Stephen Shaw of England. It explains how to run PC99 using dosemu under Linux. The information is provided in .txt, .pdf, and .odt format with links below.

.txt version
.pdf version
.odt version