旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � Programming the Tseng SVGA Chip � 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� Written for the PC-GPE by Mark Feldman e-mail address : u914097@student.canberra.edu.au myndale@cairo.anu.edu.au Please read the file SVGINTRO.TXT (Graphics/SVGA/Intro PC-GPE menu option) 旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � THIS FILE MAY NOT BE DISTRIBUTED � � SEPARATE TO THE ENTIRE PC-GPE COLLECTION. � 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 旼컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � Disclaimer � 읕컴컴컴컴컴켸 I assume no responsibility whatsoever for any effect that this file, the information contained therein or the use thereof has on you, your sanity, computer, spouse, children, pets or anything else related to you or your existance. No warranty is provided nor implied with this information. 旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴쩡컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � Identifying the Tseng SVGA Card � 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� Tseng Labs have produced two SVGA Chips, the ET3000 and the ET4000. The Tseng SVGA chips can be identified by attempting to change the Miscellaneous register as follows: Index : 06h at port 3C0h Read/write data from port 3C1h 旼컴쩡컴쩡컴쩡컴쩡컴쩡컴쩡컴쩡컴� � 7 � 6 � 5 � 4 � 3 � 2 � 1 � 0 � 읕컴좔컴좔컴좔컴좔컴좔컴좔컴좔컴� 읕쩡� High Output the value 6 to port 3C0h and read a byte from port 3C1h. Modify the high field in this byte (eg new byte = byte XOR 30h) and write this new byte to port 3C1h. Read the byte from port 3C1h and see if the byte was successfully modified, if it was then a Tseng chip is present. Having done this, write the original byte back to port 3C1h to leave the graphics adapter in it's original state. 旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴쩡컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � Identifying which Tseng Card is Present � 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� The ET4000 can be distinguished from the ET3000 by attempting to change the ET4000 Extended Start Address register as follows: Index : 33h at port 3D4h Read/write data from port 3D5h 旼컴쩡컴쩡컴쩡컴쩡컴쩡컴쩡컴쩡컴� � 7 � 6 � 5 � 4 � 3 � 2 � 1 � 0 � 읕컴좔컴좔컴좔컴좔컴좔컴좔컴좔컴� 읕쩡� 읕쩡� CAD DAD The same technique is used as was used to identify the presence of a Tseng chip, both fields should be modified, written, tested for a successful write and then restored to their original values. If the change was successful an ET4000 chip is present, otherwise an ET3000 chip is. 旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � Tseng Graphics Display Modes � 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴켸 旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � Mode Resolution Colors � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � 25h 640x480 16 � � 29h 800x600 16 � � 2Dh 640x350 256 � � 2Eh 640x480 256 � � 2Fh 640x400 256 � � 30h 800x600 256 � � 37h 1024x768 16 � � 38h 1024x768 256 � 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� All graphics modes in the above table are supported by the ET4000. I am not sure which modes are supported by the ET3000. 旼컴컴컴컴컴컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � Tseng Display Memory � 읕컴컴컴컴컴컴컴컴컴컴켸 In my opinion the Tseng memory mapping was designed to prevent graphics programmers from suffering nervous breakdowns! Two banks can be mapped to the segment A000:0000-FFFFh, one for reading and one for writing. The banks can be selected by writing to the Segment Select Registers at port 3Cdh: ET3000 Segment Select Register: Port 3CDh 旼컴쩡컴쩡컴쩡컴쩡컴쩡컴쩡컴쩡컴� � 7 � 6 � 5 � 4 � 3 � 2 � 1 � 0 � 읕컴좔컴좔컴좔컴좔컴좔컴좔컴좔컴� 읕컴쩡컴� 읕컴쩡컴� Read Write Bank Bank ET4000 Segment Select Register: Port 3CDh 旼컴쩡컴쩡컴쩡컴쩡컴쩡컴쩡컴쩡컴� � 7 � 6 � 5 � 4 � 3 � 2 � 1 � 0 � 읕컴좔컴좔컴좔컴좔컴좔컴좔컴좔컴� 읕컴컴쩡컴컴� 읕컴컴쩡컴컴� Read Write Bank Bank Both of these registers can be read from as well as written to. Each bank is 64K long, has a 64K granularity and is mapped to host memory A000:0000-FFFFh. 旼컴컴컴컴컴컴컴컴컴컴쩡컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � DPMI and the ET4000 � 읕컴컴컴컴컴컴컴컴컴컴� Apparently the ET4000 chip is capable of linear addressing in dos protect- mode programs. To enable this feature write the value 36h to port 3D4h, read the value from port 3D5h, set the lower nibble (bits 0 -> 3) to the value 1 and rewrite the value to port 3D5h. Resetting these bits to the value 0 puts the chip back in regular segmented addressing mode. I have no information where or how the entire ET4000 memory would then be mapped to linear memory. If anyone has more information on this or has a Tseng card they are willing to try it on let me know.