The SBC-188 version 3 is an update and improvement to the earlier board. This board is better suited for 80C188 operation at 25Mhz.

• Memory size is increased to 1Mb, allowing a full DOS memory of 640K plus high memory blocks.
• The 82C55 controller is configured as a PPIDE (parallel port IDE) connection; it works with hard disks as well as CF cards.
• An IDE8 connector directly on the CPU data bus is added.
• The floppy controller and connector are present. Drives may be 360K, 1.2M, 720K, or 1.44M.
• Status LEDs indicate the sequence of boot-time P.O.S.T. diagnostics.
• The Serial I/O UART connector is altered to support RTS/CTS protocol, or crossed to DTR/DSR protocol.
• The board may be used stand-alone by powering it from the IBM 4-pin peripheral connector. In this case a terminal or terminal-emulator is attached to the serial connector.
• The board may also be inserted into any RetroBrew ECB backplane to connect to peripheral boards, including the 4MEM, DualSD, ColorVDU, VGA3, etc.
• ROMs supported may be 32Kb, 64Kb, 128Kb, or 256Kb. The current BIOS recommended is 64Kb.
• The board runs MSDOS 5.0, MSDOS 6.22, and IBM PCDOS 2000 (7.0).
• Two versions now exist: 3.1 (requiring errata), and 3.2 (jumpers replace errata). The circuits are identical.

The bare 3.2 board layout, showing updated area:

The bare 3.1 board layout:

Finished board, ROM in raised ZIF socket for BIOS development & checkout:

The BOM for the 3.1 and 3.2 boards are the same except for the addition of the 3×2 pin_array.

The GAL .JED files are the same. Use sbc-188v3-gal-3.0-002.zip (above).

BIOS software is here.

Version 3 of the SBC-188 is designed to support DMA access to main SRAM memory by controllers on boards on the ECB bus. Documentation for DMA access for anyone interested in creating an I/O board that uses DMA is available above. There is at this time no such ECB board; hence, the document may not be of general interest.

The two types of Super Capacitors may be used for the RTC/NVRAM backup. Second photo shows 13.5 mm diameter cap; third photo shows a vertical mount. I used this 1.5F cap, and consider that value too large: I had to leave the board powered up overnight to get enough charge in the cap to bring the voltage above 2 volts. The good range would be 0.22F up to 0.47F. The cap in photo 2 is 0.33F.

Left photo shows the normal jumper setting for the RS-232 interface to allow RTS/CTS line protocol. The right photo shows an alternate setting which crosses RTS-CTS to DTR-DSR. This is for terminals that use the obsolete DTR/DSR line protocol. However, the programming within the UART is still RTS/CTS. If you have any doubt about which setting to use, use the one on the left.

The left photo shows a rather odd jumper (P601) labeled “INT2/INTA0”. It should always be set to “INT2” (1-2); the other setting (2-3) is for a possible future use. To the right is jumper (K601), the “Legacy/Kontron” Reset setting. In the Legacy setting (1-2) reset is put out on DIN pin C31; with the Kontron setting, DIN pin C31 is a Reset switch input to the CPU board, and the Reset signal is correctly put out on DIN pin C26 (RESOUT). All peripheral boards should also use the Kontron setting. (Kontron, a German firm, manufactured one of the earliest Zilog Z80 computers that used the 96-position DIN connector, and this was the intended pin usage.)

The right photo also shows the IBM peripheral connector, which may be used to power the board as a truly Single Board Computer, SBC-188.

The updated area on the 3.2 board is shown. P601 (INT2/INTA) is moved to be next to K601 (N8/Kontron). P805 (FDC, IDE8, PPIDE) takes over where P601 was located. It connects the interrupt outputs to the corresponding interrupt inputs on the CPU. FDC jumper is installed if the FDC controller is installed. If there is no FDC controller, then this jumper should be left off. If the IDE8 or PPIDE interfaces use interrupts, then the corresponding jumpers will need to be installed. Since the BIOS does not use interrupts on these interfaces, the normal setting will be with the jumpers off, as shown. This jumper block, P805, eliminates the 3.1 board errata, which requires disconecting the interrupts by bending up pins on U705 (74LS05).

This is a boot screen using a Wyse terminal for keyboard input and screen output:

This is the boot screen with the SBC-188 v.3 used with the VGA3 board. An IBM PC keyboard is the input device, and a VGA capable LCD monitor is used for output:

The SBC-188 is a Single Board Computer using the 80C188 CPU. General features include:

• CPU 80C188-16 w/512K SRAM
• UART 16c550
• ParPort 8255
• Floppy Controller WD37C65B
• ECB RetroBrew bus for expansion

• A 4 Megabyte memory expansion board is available.

This is the layout of the rev. 2.0 board: (anyone have a photo? I still run the 1.0 board)

Please use this space to add any notes/comments on this board that don't fit into the above sections. (Periodically, these comments may be re-arranged to be better incorporated into a new revision of the wiki page.) Please sign your comments using the wiki “Insert Signature” feature!

This is a boot screen using a Wyse terminal for keyboard input and screen output:

This is the boot screen with the SBC-188 v.3 used with the VGA3 board. An IBM PC keyboard is the input device, and a VGA capable LCD monitor is used for output:

The SBC-188 is a Single Board Computer using the 80C188 CPU. General features include:

• CPU 80C188-16 w/512K SRAM
• UART 16c550
• ParPort 8255
• Floppy Controller WD37C65B
• ECB RetroBrew bus for expansion

• A 4 Megabyte memory expansion board is available.

This is the layout of the rev. 2.0 board: (anyone have a photo? I still run the 1.0 board)

Please use this space to add any notes/comments on this board that don't fit into the above sections. (Periodically, these comments may be re-arranged to be better incorporated into a new revision of the wiki page.) Please sign your comments using the wiki “Insert Signature” feature!