Semi-Virtual Diskette (SVD)
TI 99/4a

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Connecting  -  Using   -  Trouble Shooting   -  Supported Features   -  Finding Diskette Images

Connecting the SVD to the TI99/4a

Connecting the SVD to the TI99/4a is very straight forward. There are a couple of requirements and issues that you need to check-out first:
  • To use the SVD you need the Peripheral Expansion System or Disk Drive Controller just like you would with a real floppy disk drive.
  • You need an appropriate 34-pin edge-card connector cable (more on this below).
  • Depending upon if you want to have a real floppy drive along with the SVD, you'll need to worry more about termination.

Simple SVD-only Connection

By far the easiest way to connect the SVD to the TI99/4a is to connect it as the only external floppy. If you are using the Peripheral Expansion System, you most likely will have an internal floppy installed.


Connect the Peripheral Expansion System or Disk Drive Controller

The expansion system and controller both plug into the expansion bay on the right side of the TI99/4a. In the case of the expansion system, you will plug in the cable connector, in the case of the controller, the entire unit plugs into the side of the TI99/4a.


Plug in the Disk Manager (II)

If you have a Disk Manager (or Disk Manager II) cartridge, you can plug that in to the front of the TI99/4a. NOTE that the the cartridge isn't necessary to use the SVD or floppy. However, it contains many programs that make it easier to list the contents of the floppy or copy one floppy to another. I highly recommend using it.


Use the Terminated SVD connector

Plug the terminated SVD connector into the left-side 34-pin plug on the SVD. The terminated connector is necessary since the SVD will be the only "floppy" connected to the expansion system or the controller. In the case of the exansion system, there will probably be another drive available, but it will be connected to a different internal connector other than the SVD. For more information on termination, see the termination section in Getting Started.


Connect the SVD to the expansion system or controller

To do this, you need a straight-through 34-pin edge card connector cable. Pay close attention to the orientation of the cable, ensuring that the stripe for cable is on the correct side for both the controller cart and the SVD. The SVD is clearly marked with the location of the "stripe". However, the best indication of the right orientation is the notch that is taken out of the edge-card connector for both the SVD and the controller. Make sure these line up!

Odd Notch

Note that the edge-card connector at the back of the Expansion Chassis for the TI99/4a is just a bit odd. Although it is a 34-conductor cable with the same pin-out as the "standard" floppy interface for the vintage, it has a notch in an odd place.

Normally the notch is between pins 3 and 5. But the notch for the TI99/4a controller is between pins 9 and 11.

This is not fatal. If you don't have the special edge-card connector with the polarizing plastic key in the right spot, then just remove the key to make it work, or use a connector without a key. HOWEVER, be sure that you align the stripe on the floppy cable closest to the connector side with the notch.

Using the TI 99/4a with the SVD

Booting from the SVD

Unlike many vintage computers (but like the TRS-80 CoCo), the TI99/4 doesn't read the operating system (OS) from floppy when "booting." The OS is contained in the disk controller cartridge as described above. This makes booting very easy.

So, there is nothing special you have to do to boot from the SVD. Just plug the disk controller cartridge in, turn on the TI99/4a and it boots. See below for an example.

Sample Directory Listing

Running a Program

Copying a Floppy

Other Things

TI99/4a - Trouble Shooting

TI99/4a - Supported Features

support for v9t9, TIDisk, and pc99 disk image formats
requires a floppy controller either in the Peripheral Expansion System or the Disk Drive Controller
supports commands from the Disk Manager (and Disk Manager II)
reading the diskette image
writing the diskette image
formatting the diskette image
downloading individual files - downloading individual BASIC programs or command files
single sided double & single density
double sided - this will be supported with the SVD II to be release late 2005

TI99/4a - Links to Images A poplular place for TI99 images and information. There are MANY disk images here of all types. Note, however, that they are named in many different ways and you may need to rename them to get them to work with the SVD.
File ExtensionCommon MachineDescription
.v9t9 TI99/4a This format is also known by .t99 and .tidisk. It is a binary data format with contiguous sectors. There is no header information and it is, therefore, impossible to distinguish between DS SD and DD SS images looking only at the size of the file. These files are normally 40 tracks with 9 sectors and in single density.
.pc99 TI99/4a The .pc99 format is a raw dump of disk sector data and includes sector header information.
.dsk TI99/4a Both .pc99 and .v9t9 formats can be named a .dsk file. This often raises issues because the SVD finds it hard to distinguish between these file formats and many others. When using these formats, it is wise to name with an extension of something other than .dsk.