Reply 20 of 114, by Great Hierophant
The technical manual can also be found attached to the scans of the Tandy 1000 HX and TX Technical Manuals, found here : ftp://ftp.oldskool.org/pub/tvdog/tandy1000/documents/ The site you linked to had the important pages intact.
C0 and C1 are used by DMA4 in an AT and the card cannot assert any DRQ or DACK signals on the ISA bus, so you may be safe with the limitation that you cannot use Tandy sound and a 16-bit DMA channel at the same time. I am not aware of any program that would possibly use both at the same time. However, if a sound card or other device like a network or a SCSI card made use of DMA channels 5, 6 or 7, then you may hear unwanted sounds from the sound card.
There are two solutions to this issue. First, you could limit the card so that it only responds to C0 and C1 and 1E0 and 1E1. Second, you could use a switch accessible from the back of the card to disable the sound chip when it is not going to be used. Unless someone can find examples of a game that uses C2-C7, I think the first solution would be best and it only requires replacing the 8-bit comparator with a 10-bit comparator, the 74LS460.
There was a Sound Blaster emulator for the PC Speaker and Covox called Virtual Sound Blaster, made by the same guy that wrote TEMU, so if that is possible, emulating the DAC of the Tandy PSSJ should certainly be possible : Sound Blaster Emulator for Dos?
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