Tandy TRS-80 model II bus cards

For now, mainly the images I could find. More comment to be added.

Some images are borrowed from www.vintage-computer.com or elsewhere. (CPU)
CPU MODULE 8709049, REV B, ©1979 (Thanks to Ruud Broers for the image.)
CPU MODULE 8709049, REV C, ©1979

CPU MODULE 8709049, REV D, ©1979

MEMORY BOARD 32 or 64 kByte card. The upgrade to 64kByte for a 32 kByte system (half populated card) was sold as 26-4105 (adding another half populated card). See the Model II page for jumper information for this card.
8709053, REV B, ©1979. RS No. 26-4105.

MEMORY BOARD Another memory board, apparently for 16kByte to 48kByte RAM. Chip dates indicate 1983-1984 as production date. RS No. 26-6503. See this thread at www.vcfed.org/forum/ for more info on its usage.(Thanks to Peter Cetinski for the image.)

MMU Extender The 68000 on the Model II bus could standard address just 1 MByte without bankswitching. At one time Tandy produced a "MMU Extender" which made adressing up to 4 MByte possible. Because of physical limitations, 2 or 3 MByte was more customary. This board is produced in just one extremely small order of 255 pieces. (Source: Frank Durda IV in comp.sys.tandy: "4 MEG memory board for model 6000"). (Thanks to Peter Cetinski for the image.)
FDC Interface
REV B Note the small satellite board, also present on rev A. The B revision also exists without the satellite board but with an on board modification with spare gates of U37 (Thanks to Ruud Broers for the info.).
This card needs the loopback plug if no Disk System is connected.
8709063, REV B, ©1979

FDC Interface
REV C This card needs the loopback plug if no Disk System is connected.
8709063, REV C, ©1979

FDC Interface
"Late Design" This board has separate connectors and termination for the internal disk drive (J0) and the Disk Station (P1), making the loopback plug unneeded. Two 34 pin connectors (J1 and J2) are in preparation for 5 1/4" drives and should work with little modification. Tandy never deployed 5 1/4" drives for the M II line.
8709198, REV " ", LEIMV-1, 3681, TANDY CORP. ©1980

M2 VIDEO KEYBOARD INTERFACE 8709048, REV C, ©1979

M12 VIDEO KEYBOARD INTERFACE This is the only card in the Model 12. It might also be found in the 16B and 6000 card cage.

Graphics Card This card is connected with two flatcables to the Video Keyboard Interface. It is actually just a graphics extension to the standard video. Both the 6845 and the character ROM of the Video Keyboard Interface are moved to the Graphics Card and replaced by flatcables. The video signal with the graphics is still emitted from the VKI.
8709261, REV A, ©1981, Prod # 26-4104

Type #1 Hard Disk Interface This is the old style external hard drive controller. Works with the 8MB drives only. The interface is a modified WD1002HD0 one, adding an address line for the Tandy specific Disk present and write protect registers.
This board contained the I/O-port address decoding for the C0h-CFh region, lacking on the newer interface, where it was integrated in the controller.
8709200, REV ?
Type #2 Hard Disk Interface The interface to the controller is actually a Model III or 4 I/O bus. The 16 kByte RAM was still there, as TRSDOS II needed at least 96 kByte of RAM.
This card was used with controller types #2 and #3
8709295, Tandy Corp. 1981

Single ST412 Interface/controller #4 This is a single board, dual hard disk variant of the hard disk interface and controller boards. It is used for the internal hard disk in the Model 16b and 6000. It contains the Z80-CTC and 16 kByte RAM (static this time) of the old interface and the WD1100 and WD1010 of the controller. It was intended to be compatible with the previous WD1010 controller.
On Frank Durda's overview this is controller #4.
REV PP2, TANDY CORP, ©1983

Corvus card An interface to a Corvus system, probably hard disk controller. Borrowed this image from http://www.vintagecomputer.net/tandy/.

MC68000 CPU Part of the "Model 16 Enhancement Option" 26-6010. Runs at 6 MHz.
8709235, PP4, PCC M2 94VO 8212, ©1981

New MC68000 CPU The improved 68000 CPU card for the Tandy 6000. Runs at 8 MHz.

128 - 256 kByte RAM
MC68000 Memory Part of the "Model 16 Enhancement Option" sold as 26-6010. 128 or 256 kByte RAM.
8709236, LEI MV-1©1981

New 128 - 256 kByte RAM
MC68000 Memory The improved 68000 memory card for the Tandy 6000. RS No. 26-6011. The RAM is 26-6012.

256 - 512kByte
MC68000 Memory This might work only with the newer 68k CPU. Probably found only in the 6000. The board might be the same as the new 128 - 256 kByte RAM card, but configured for larger RAM chips. RS No. 26-6015, The RAM is 26-6016.

Bernoulli Box Interface

3 RS232 port interface Prod # 26-6013

4 RS232 port interface Referred to by Frank Durda IV in "comp.sys.tandy: TRS-80 Model II Emulator? _ 200,000 Model I's". (Thanks to Peter Cetinski for the image.)

ARCNET interface board Support for this board was in TRSDOS II 4.3. (Thanks to Peter Cetinski for the image.)

Veritas Dual Processor Option board A rare board for the Model II line. If you could have 68000/Xenix, why settle for limited 8088/MSDOS compatibility? Still lots of computers in the day had upgrades like this. (Thanks to Peter Cetinski for the image.)

4K EPROM board This "Tandy Model II 4K EPROM board Version 1.0" enables the use of a custom boot ROM. It has room for 2 ROMs (or EPROMs) that are selected by jumper. Size of the ROM can be 2K (2716) or 4K (2732). The flat cable connects to the socket of the original 2K ROM on the CPU board. An extra wire is used to enable 4K EPROM usage. The original ROM can be mounted on the board. BigTMon is the name of the custom monitor program. BigTMon includes functions like memory bank check, memory display and edit, port view and edit, hex dump to serial port, hex load from serial port, basic serial terminal and keyboard check. The first time the board and BigTMon monitor were shown was at Tandy Assembly 2019.

The hard disk interface cards shown above can only be connected to certain hard disk controller cards.

8x300 based hard disk controller #1 This is the original, 512 byte sector only hard disk controller for the Model II line based on the 8x300. The size is 29 x 21.5 cm. This board had the standard WD1010 registers at I/O port C8h-CFh. C0h and C1h were used for write protect and drive present registers.

8x300 based hard disk controller #2 This is the second 256 and 512 byte sector hard disk controller used for the Model III and 4 line based on the 8x300. The size is 29 x 21.5 cm. (Thanks to Pascal Holdry for the image.)

WD1010 based hard disk controller #3 Smaller than the #2 controller, 20.5cm x 14.5cm, and based on the WD1010 and support logic. Used in the TRS-80 15 Meg disk system, cat. no. 26-4155. Very similar to the WD1002 board (-05 or -HD0), but this included the Tandy specific write protect and disk present registers. The "TB1" could stand for "Tandy Batch 1".
(Thanks to Ian Mavric for the image.)

Local links

The Model II
Enhanced Model II or the Model 16
Model 12
Eight Meg Disk System
TECHNICAL BULLETIN INDEX for the Model II as text (all bulletins as PDF in the virtual library)
TECHNICAL BULLETIN INDEX for the Model 16 as text (all bulletins as PDF in the virtual library)
TECHNICAL BULLETIN INDEX for the Model 12 & 16B as text (all bulletins as PDF in the virtual library)
TECHNICAL BULLETIN INDEX for the Model 6000 as text (all bulletins as PDF in the virtual library)
Virtual library

External links

Last update: 2020-03-30

fjkraan@xs4all.nl

CPU MODULE		8709049, REV B, ©1979 (Thanks to Ruud Broers for the image.)
CPU MODULE		8709049, REV C, ©1979
CPU MODULE		8709049, REV D, ©1979
MEMORY BOARD		32 or 64 kByte card. The upgrade to 64kByte for a 32 kByte system (half populated card) was sold as 26-4105 (adding another half populated card). See the Model II page for jumper information for this card. 8709053, REV B, ©1979. RS No. 26-4105.
MEMORY BOARD		Another memory board, apparently for 16kByte to 48kByte RAM. Chip dates indicate 1983-1984 as production date. RS No. 26-6503. See this thread at www.vcfed.org/forum/ for more info on its usage.(Thanks to Peter Cetinski for the image.)
MMU Extender		The 68000 on the Model II bus could standard address just 1 MByte without bankswitching. At one time Tandy produced a "MMU Extender" which made adressing up to 4 MByte possible. Because of physical limitations, 2 or 3 MByte was more customary. This board is produced in just one extremely small order of 255 pieces. (Source: Frank Durda IV in comp.sys.tandy: "4 MEG memory board for model 6000"). (Thanks to Peter Cetinski for the image.)
FDC Interface REV B		Note the small satellite board, also present on rev A. The B revision also exists without the satellite board but with an on board modification with spare gates of U37 (Thanks to Ruud Broers for the info.). This card needs the loopback plug if no Disk System is connected. 8709063, REV B, ©1979
FDC Interface REV C		This card needs the loopback plug if no Disk System is connected. 8709063, REV C, ©1979
FDC Interface "Late Design"		This board has separate connectors and termination for the internal disk drive (J0) and the Disk Station (P1), making the loopback plug unneeded. Two 34 pin connectors (J1 and J2) are in preparation for 5 1/4" drives and should work with little modification. Tandy never deployed 5 1/4" drives for the M II line. 8709198, REV " ", LEIMV-1, 3681, TANDY CORP. ©1980
M2 VIDEO KEYBOARD INTERFACE		8709048, REV C, ©1979
M12 VIDEO KEYBOARD INTERFACE		This is the only card in the Model 12. It might also be found in the 16B and 6000 card cage.
Graphics Card		This card is connected with two flatcables to the Video Keyboard Interface. It is actually just a graphics extension to the standard video. Both the 6845 and the character ROM of the Video Keyboard Interface are moved to the Graphics Card and replaced by flatcables. The video signal with the graphics is still emitted from the VKI. 8709261, REV A, ©1981, Prod # 26-4104
Type #1 Hard Disk Interface		This is the old style external hard drive controller. Works with the 8MB drives only. The interface is a modified WD1002HD0 one, adding an address line for the Tandy specific Disk present and write protect registers. This board contained the I/O-port address decoding for the C0h-CFh region, lacking on the newer interface, where it was integrated in the controller. 8709200, REV ?
Type #2 Hard Disk Interface		The interface to the controller is actually a Model III or 4 I/O bus. The 16 kByte RAM was still there, as TRSDOS II needed at least 96 kByte of RAM. This card was used with controller types #2 and #3 8709295, Tandy Corp. 1981
Single ST412 Interface/controller #4		This is a single board, dual hard disk variant of the hard disk interface and controller boards. It is used for the internal hard disk in the Model 16b and 6000. It contains the Z80-CTC and 16 kByte RAM (static this time) of the old interface and the WD1100 and WD1010 of the controller. It was intended to be compatible with the previous WD1010 controller. On Frank Durda's overview this is controller #4. REV PP2, TANDY CORP, ©1983
Corvus card		An interface to a Corvus system, probably hard disk controller. Borrowed this image from http://www.vintagecomputer.net/tandy/.
MC68000 CPU		Part of the "Model 16 Enhancement Option" 26-6010. Runs at 6 MHz. 8709235, PP4, PCC M2 94VO 8212, ©1981
New MC68000 CPU		The improved 68000 CPU card for the Tandy 6000. Runs at 8 MHz.
128 - 256 kByte RAM MC68000 Memory		Part of the "Model 16 Enhancement Option" sold as 26-6010. 128 or 256 kByte RAM. 8709236, LEI MV-1©1981
New 128 - 256 kByte RAM MC68000 Memory		The improved 68000 memory card for the Tandy 6000. RS No. 26-6011. The RAM is 26-6012.
256 - 512kByte MC68000 Memory		This might work only with the newer 68k CPU. Probably found only in the 6000. The board might be the same as the new 128 - 256 kByte RAM card, but configured for larger RAM chips. RS No. 26-6015, The RAM is 26-6016.
Bernoulli Box Interface
3 RS232 port interface		Prod # 26-6013
4 RS232 port interface		Referred to by Frank Durda IV in "comp.sys.tandy: TRS-80 Model II Emulator? _ 200,000 Model I's". (Thanks to Peter Cetinski for the image.)
ARCNET interface board		Support for this board was in TRSDOS II 4.3. (Thanks to Peter Cetinski for the image.)
Veritas Dual Processor Option board		A rare board for the Model II line. If you could have 68000/Xenix, why settle for limited 8088/MSDOS compatibility? Still lots of computers in the day had upgrades like this. (Thanks to Peter Cetinski for the image.)
4K EPROM board		This "Tandy Model II 4K EPROM board Version 1.0" enables the use of a custom boot ROM. It has room for 2 ROMs (or EPROMs) that are selected by jumper. Size of the ROM can be 2K (2716) or 4K (2732). The flat cable connects to the socket of the original 2K ROM on the CPU board. An extra wire is used to enable 4K EPROM usage. The original ROM can be mounted on the board. BigTMon is the name of the custom monitor program. BigTMon includes functions like memory bank check, memory display and edit, port view and edit, hex dump to serial port, hex load from serial port, basic serial terminal and keyboard check. The first time the board and BigTMon monitor were shown was at Tandy Assembly 2019.

8x300 based hard disk controller #1		This is the original, 512 byte sector only hard disk controller for the Model II line based on the 8x300. The size is 29 x 21.5 cm. This board had the standard WD1010 registers at I/O port C8h-CFh. C0h and C1h were used for write protect and drive present registers.
8x300 based hard disk controller #2		This is the second 256 and 512 byte sector hard disk controller used for the Model III and 4 line based on the 8x300. The size is 29 x 21.5 cm. (Thanks to Pascal Holdry for the image.)
WD1010 based hard disk controller #3		Smaller than the #2 controller, 20.5cm x 14.5cm, and based on the WD1010 and support logic. Used in the TRS-80 15 Meg disk system, cat. no. 26-4155. Very similar to the WD1002 board (-05 or -HD0), but this included the Tandy specific write protect and disk present registers. The "TB1" could stand for "Tandy Batch 1". (Thanks to Ian Mavric for the image.)