# DECtalk PC and SCSI II/CD ROM Readers

We have found that there might be a time when your SCSI 2 adapter and/or CD ROM Reader will not work when a DECtalk PC is installed.

The problem occurs when the DECtalk PC is set to an I/O address used by the SCSI 2 adapter. If the adapter driver finds a DECtalk PC at an I/O address it wants to use it may hang the system. Additionally the utility DT_CONF.EXE tries to find and initialise any DECtalk PC modules at the following I/O base addresses: 240, 250, 340 and 350.

If the SCSI 2 adapter also uses one of these I/O base addresses for a "mailbox", when DECtalk's DT_CONF.EXE utility tries to query it, devices on the SCSI 2 bus like a CD ROM drive may no longer work.

In order to work around this conflict we have added switches to the DT_CONF and DT_DRIV commands which cause the DECtalk to be initialised only at a single otherwise unused I/O address.

If you find you are having a problem getting your system to boot or accessing your CD ROM Reader after installing the DECtalk PC, power down your PC and remove the DECtalk. Reboot your system to insure that it boots up satisfactorily and check the CDs operation to insure that it is the DECtalk PC causing the problem.

If it is, you will need to change the switch settings on your DECtalk to correspond to the I/O address you want to use. There isn't any hard and fast rule as to which address is open in your PC. If you have a Sound Blaster 16 card and a SCSI II interface card in your PC, address 250 has worked. The I/O addresses used depends on what SCSI adapter you are using e.g. Adaptek, Trantor, Ultrastor etc. or your CD ROM reader may come with its own adapter card or your sound card may have an adapter built-in.

Determining which I/O addresses are used by the various devices in you PC can be a challenge. A proposed procedure for finding out which ones are used is as follows:

1. Many devices when they install their drivers at boot up will report on the screen what I/O address they are using. This information will usually scroll by too quickly to be read. MS-DOS V6.x provides the capability to individually run each command line in the PC's CONFIG.SYS and AUTOEXEC.BAT files at start-up.

To utilise this feature reboot your system. When the "Starting MS-DOS..." message appears on the screen and the system emits a beep from its speaker, quickly press the F8 key. You will then be prompted before each line in the files are run. Press the "Y" key when you are prompted with a new line. After the line has been executed you will normally be given information back as a result of executing that line. The ones to particularly observe are the commands which load the drivers for adapters/options which are installed in your PC. When these drivers are initiated they will report back as to what system resources they are using such as COM/LPT ports, IRQs and I/O addresses. Take note as to which I/O addresses are being used. For instance a Sound Blaster 16 with a SCSI II interface adapter for a CD ROM could utilise I/O address 220 for the sound card and 340 for the SCSI II interface.

In this particular case we found that we could also not use I/O address 350 even though we could not determine if any device was using it. Apparently the Sound Blaster will sometime use part of the next higher I/O address e.g. 340 and part of 350.

2. Select the first I/O address that does not seem to be used by any other device. In the example above, we selected I/O address 250 because it seemed to be the best candidate. To have the DECtalk only use this I/O address during system boot we needed to add "switches" to command lines in two files. You do this by editing the DT.BAT file in the DECtalk's file directory (the default is DECTALK) and the AUTOEXEC.BAT file in the system root directory (usually C:\). On the lines that say DT_CONF and DT_DRIV -C, add the -b xxx switch where xxx is the selected base I/O address. For example, in the case we have been describing where we have selected I/O address 250, the command lines would look like this:

DT_CONF -b 250

DT_DRIV -c -b 250

Save the files after you have edited them.

3. You will also need to set the selected I/O address on the DECtalk PC board. You should turn off your PC and remove the DECtalk board. Locate the switch pack on the board and set the switches accordingly.

The Install/User Guide describes how to set the switches and what are the available switch settings. In the case described, I/O address 250 was set by setting switch 6 to ON and all the rest to OFF.

Reinstall the DECtalk PC in your PC making sure that the speaker is plugged in. Restart the computer and repeat the line-by-line boot process described above. Observe the same driver load lines as before and be sure that each appears to load satisfactorily. If a particular device doesn't appear to load satisfactorily or the system stops when you try to run a line, then their probably is still a conflict between that device's settings and the DECtalk's.

4. Referring to the device's installation manual may provide information as to the I/O addresses it uses as defaults and what other addresses can be set. Try changing the device's I/O address to one not available on the DECtalk and not used by any another device.

5. Repeat this process until you get a satisfactory system start-up and the DECtalk speaks its start-up message and you can access the CD ROM's directory or use/configure the device that was having the conflict.

If you are running more than one DECtalk PC card in your system your DT.BAT and AUTOEXEC.BAT file(s) should include the base address of each card. For cards that are set at I/O addresses 240 and 350 the command lines would look like the following:

DT_CONF -b 240

DT_CONF -b 350

DT_DRIV -c -b 240 -c -b 350

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