First post, by jnnelson79
Hey everyone! I thought I'd share my Retro Success Story today for anyone else who might be trying to make something like this work!
I have a Tandy 1000 TL/2, and I love the Tandy DAC and the Tandy 3 Voice Sound Chip as well. However, some games don't use either one, and I really wanted a Sound Blaster to have that awesome OPL2 and Sound Blaster DAC. I also wanted a regular 15 pin Game Port, so the Sound Blaster solved both issues. Except it didn't.... The Tandy DAC wouldn't work with the Sound Blaster installed.
The Sound Blaster is a version 2.0 CT1350B card for anyone wondering. I did lots of research online and found several sources stating that Sound Blaster DAC and Tandy DAC would not work together because they both use IRQ 7 and DMA 1. The Tandy DAC can't be changed at all... it's hard wired to those settings. The Sound Blaster has jumpers for IRQ, but it will only use DMA 1 and requires DMA for the DAC. That's why several sources say these devices won't work together and that installing a Sound Blaster will render the Tandy DAC inoperative, but the 3 voice sound still works. However, this was unacceptable to me because it rendered certain games inoperable such as Outrun that finds the Tandy DAC in the system, tries to use it, and freezes the system. Basically, any program that tries to use the Tandy DAC when there is a DMA conflict like this will immediately freeze the system.
So, I looked at the Sound Blaster CT1350B Schematic and saw that there is actually also a jumper for DMA Sharing as well as a jumper to enable or disable DMA. However, the manual clearly states not to remove the DMA enable or disable jumper, and my understanding is that this will make the Sound Blaster DAC stop working. Therefore, I asked around on this board, and keenmaster486 replied and felt that enabling DMA sharing was worth a try. I should also mention that my CT1350B was already set to IRQ5 with the jumpers as well.
So, I tried it, and surprisingly, it worked perfectly!!! I can now use the Tandy DAC and the Sound Blaster DAC on this machine! Of course, you can't use them at the same time, but I haven't come across any program or game that will even try them both at the same time. So, I was really excited! Retro Success!!
Here is a link to the schematic - https://stason.org/TULARC/pc/sound-cards-mult … R-2-0-CT13.html
To enable DMA Sharing, I just moved JP14 from the default right position to the left position as indicated on the schematic. Hope this helps someone in the future who may be searching like I was! If not, I hope you at least enjoyed reading a retro success story!