IBM XT Compatible Processor Board based on Faraday FE2010/FE2010A chipset
Micro 8088 is an easy to build IBM PC/XT compatible processor board. It uses a fairly common Faraday FE2010/FE2010A chipset, that implements most of IBM PC/XT LSIs (Intel 8xxx ICs) and glue logic. Micro 8088 uses SRAM ICs to implement the system RAM, and a Flash ROM IC to store the BIOS, further reducing the number of components, and simplifying the build process.
- Processor: Intel 8088 or compatible, NEC V20
- Supports IBM PC/XT standard 4.77 MHz CPU frequency and, when using FE2010A chipset, 7.16 MHz and 9.54 MHz CPU frequencies
- Coprocessor: Intel 8087
- Faraday FE2010/FE2010A chipset, implementing the following components:
- One 8237 direct memory access controller (DMAC)
- One 8259 programmable interrupt controller (PIC)
- One 8254 programmable interval timer (PIT)
- One 8255 programmable peripheral interface (PPI)
- Clock generation, and glue logic
- RAM: 512 KiB or 640 KiB base memory; Up to 192 KiB UMBs. Implemented using SRAM
- ROM: 64 KiB. Implemented using 128 KiB Flash ROM
- 8-bit ISA interface
- PS/2 compatible keyboard connector; built in AT2XT converter
Please refer to Building Instructions page for detailed instructions.
Please refer to Faraday FE2010A documentation and Faraday FE2010 datasheet for detailed information about Faraday FE2010/FE2010A chipsets.
Note: CPU clock frequency switching (turbo mode) is only implemented in Faraday FE2010A chipset (not in FE2010).
| Pin | Description |
|---|---|
| 1 | Keyboard data |
| 2 | Unused |
| 3 | GND |
| 4 | +5V |
| 5 | Keyboard clock |
| 6 | Unused |
| Pin | Description |
|---|---|
| 1 | Speaker output |
| 2 | Internal Speaker input* |
| 3 | Unused |
| 4 | +5V |
Note: To enable internal speaker connect a jumper across pins 1-2
| Pin | Description |
|---|---|
| 1 | Reset input |
| 2 | Ground |
| Position | Description |
|---|---|
| open (default) | Map lower 64 KiB of the Flash ROM to 0xF0000-0xFFFFF |
| closed | Map upper 64 KiB of the Flash ROM to 0xF0000-0xFFFFF |
| Position | Description |
|---|---|
| open | Use 14.31818 MHz crystal |
| closed (default) | Use 28.63636 MHz crystal |
Note: 14.31818 MHz crystal supports 4.77 MHz and 7.16 MHz CPU clock frequencies; 28.63636 MHz crystal additionally supports 9.55 MHz CPU clock frequency
| Position | Description |
|---|---|
| open (default) | Use SPLD (U16) |
| closed | Use FE2010A (U3) |
Note: FE2010A only generates RAM chip select for the base RAM (lower 640 KiB). It does not generate RAM chip select for UMBs, and therefore SPLD (U16) is required to implement UMBs
| Position | Description |
|---|---|
| open (default) | Use SPLD (U16) |
| closed | Use FE2010A (U3) |
Note: FE2010A does not generate chip select for memory write cycles, therefore it does not support in-system BIOS upgrades
Press SW1 to reset the system
| Position | Description |
|---|---|
| SW2.1 = OFF, SW2.2 = OFF | MDA or Hercules |
| SW2.1 = ON, SW2.2 = OFF | CGA, 80x25 |
| SW2.1 = OFF, SW2.2 = ON | CGA, 40x25 |
| SW2.1 = ON, SW2.2 = ON | None, EGA, or VGA |
| SW2.3 = OFF | Disable keyboard 0xE0 scan code pass through |
| SW2.3 = ON | Enable keyboard 0xE0 scan code pass through |
| Position | Description |
|---|---|
| SW3.1 = ON | Map 0xC0000-0xC7FFF to RAM |
| SW3.2 = ON | Map 0xC8000-0xCFFFF to RAM |
| SW3.3 = ON | Map 0xD0000-0xD7FFF to RAM |
| SW3.4 = ON | Map 0xD8000-0xDFFFF to RAM |
| SW3.5 = ON | Map 0xE0000-0xEFFFF to RAM |
Note: SPLD (U16) is required to implement UMBs. This switch is not used in systems without SPLD
Micro 8088 project on Mouser.com - View and order all components except of the Faraday FE2010A chipset, and the PCB. Micro 8088 project on OSH Park - View and order the PCB.
| Component type | Reference | Description | Quantity | Possible sources and notes |
|---|---|---|---|---|
| PCB | Micro 8080 PCB - Version 1.1 | 1 | Refer to the RetroBrew Computers Board Inventory page for ordering information, or order from a PCB manufacturer of your choice using provided Gerber or KiCad files | |
| Integrated Circuit | U1 | Intel 8088, 80C88, or NEC V20 CPU | 1 | eBay, Mouser (expensive) - 968-IP80C88-2 |
| Integrated Circuit | U2 | Intel 8087 FPU | 1 | Optional, eBay |
| Integrated Circuit | U3 | Faraday FE2010A | 1 | eBay |
| Integrated Circuit | U4 | SST39SF010A Flash ROM, DIP-32 package | 1 | Mouser 804-39SF010A7CPHE |
| Integrated Circuit | U5, U6 | AS6C4008 SRAM, DIP-32 package | 2 | Mouser 913-AS6C4008-55PCN |
| Integrated Circuit | U7 - U9 | 74F573 Octal D-Type Latch | 3 | Mouser 595-SN74F573N |
| Integrated Circuit | U10, U11 | 74F245 Octal Bus Transceiver | 2 | Mouser 595-SN74F245N |
| Integrated Circuit | U12, U13 | 74F244 Octal Buffer | 2 | Mouser 595-SN74F244N |
| Integrated Circuit | U14 | 74F00 Quad 2-Input NAND Gate | 1 | Optional - install either U14 or U16. Mouser 595-SN74F00 |
| Integrated Circuit | U15 | PIC12F629 Microcontroller | 1 | Mouser PIC12F629-I-P |
| Integrated Circuit | U16 | ATF16V8B SPLD | 1 | Optional - install either U14 or U16. Mouser 556-AF16V8B15PU |
| IC Socket | U1, U2 | DIP-40, 600 mil socket | 2 | Mouser 517-4840-6000-CP |
| IC Socket | U3 | PLCC-84 through hole socket | 1 | Mouser 517-8484-11B1-RK-TP |
| IC Socket | U4-U6 | DIP-32, 600 mil socket | 3 | Mouser 517-4832-6000-CP |
| IC Socket | U7-U13, U16 | DIP-20, 300 mil socket | 8 | Mouser 517-4820-3000-CP |
| IC Socket | U14 | DIP-14, 300 mil socket | 1 | Mouser 517-4814-3000-CP |
| IC Socket | U15 | DIP-8, 300 mil socket | 1 | Mouser 517-4808-3000-CP |
| Diode | D1 | 1N4148 | 1 | Mouser 512-1N4148 |
| LED | D2 | 3 mm, green LED indicator | 1 | Mouser LTL-4231NHBP |
| Transistor | Q1 | PN2222A, 2.54mm lead spacing | 1 | Mouser 512-PN2222ATA |
| Crystal | X1 | 28.63636 MHz, 18 pF, HC-49/S | 1 | Mouser 717-9B-28.63636MAAJB |
| Speaker | SP1 | 12 mm speaker | 1 | Mouser 665-AT-1224TWTR |
| Tactile Button | SW1 | 6 mm tactile button, right angle | 1 | Mouser 653-B3F-3152 |
| DIP Switch | SW2 | 3 positions | 1 | Mouser 774-2063 |
| DIP Switch | SW3 | 5 positions | 1 | Mouser 774-2065 |
| Connector | P1 | 6 pin Mini DIN, purple | 1 | Mouser 806-KMDGX-6S-BS2715C |
| Pin Header | P2, JP3-JP4 | 4 pin header, 2.54 mm pitch | 2 | Mouser 649-68002-104HLF |
| Pin Header | P3, JP1-JP2 | 2 pin header, 2.54 mm pitch | 3 | Mouser 649-68002-102HLF |
| Capacitor | C1 - C17 | 0.1 uF, MLCC, 5 mm lead spacing | 17 | Mouser 594-K104K15X7RF53H5 |
| Capacitor | C18 - C20 | 10 uF, MLCC, 5 mm lead spacing | 3 | Mouser 810-FG24X7R1A106KRT0 |
| Trimmer Capacitor | C21 | 6.5-30 pF, 5 mm lead spacing | 3 | Mouser 659-GKG30015 |
| Capacitor | C22 | 47 pF, MLCC, 5 mm lead spacing | 1 | Mouser 75-1C20C0G470J050B |
| Capacitor | C23 | 0.01 uF, MLCC, 5 mm lead spacing | 1 | Mouser 594-K103K15X7RH5TH5 |
| Resistor Array | RR1 | 4.7 k, bussed, 10 pin SIP | 1 | Mouser 266-4.7K-RC |
| Resistor Array | RR2 | 10 k, bussed, 10 pin SIP | 1 | Mouser 266-10K-RC |
| Resistor Array | RR3, RR4 | 4.7 k, bussed, 6 pin SIP | 2 | Mouser 264-4.7K-RC |
| Resistor Array | RR5 | 10 k, bussed, 6 pin SIP | 1 | Mouser 264-10K-RC |
| Resistor | R1 | 33 ohm, through hole | 1 | Mouser 291-33-RC |
| Resistor | R2, R3 | 47 ohm, through hole | 2 | Mouser 291-47-RC |
| Resistor | R4, R5 | 470 ohm, through hole | 2 | Mouser 291-470-RC |
| Resistor | R6 | 1 kohm, through hole | 1 | Mouser 291-1K-RC |
| Resistor | R7 | 10 kohm, through hole | 1 | Mouser 291-10K-RC |
| Resistor | R8 | 1 Mohm, through hole | 1 | Mouser 291-1M-RC |
| Fuse | F1 | 1.1A polyfuse, 5.08 mm lead pitch | 1 | Mouser 576-16R110BPR |
| ISA Bracket | Keystone Electronics 9202 | 1 | Mouser 534-9202 | |
| Screw | 4-40 x 1/4" Screw | 2 | Mouser 534-9900 |
Micro 8088 uses a modified version of Xi 8088 BIOS. The BIOS binary images are provided in BIOS directory. The BIOS source code is available in 8088_bios GitHub repository
The BIOS keyboard handler uses the following key combinations to switch the CPU clock frequency:
- Ctrl-Alt-Keypad - - Normal 4.77 MHz CPU clock frequency
- Ctrl-Alt-Keypad * - Turbo 7.16 MHz CPU clock frequency
- Ctrl-Alt-Keypad + - Turbo 9.55 MHz CPU clock frequency (works only on systems with 26.63636 MHz X1 crystal)
Note that the BIOS does not, and possibly can not check if the installed CPU and the FPU are actually capable of running at higher clock frequencies. Turning on the turbo mode in a system with 5 MHz CPU can make it unstable.
Micro 8088 integrates an AT2XT keyboard converter, implemented using PIC12F629 (U15). The firmware for this microcontroller is availabe from Vintage Computer Federation AT2XT page. The HEX file with the firmware can be extracted from XTATKEY_094.zip.
An optional ATF16V8/GAL16V8 SPLD (U16) allows using spare SRAM space for UMBs, and implements Flash ROM write access. The fuse maps for the SPLD are provided in SPLD directory of this repository. The SPLD/micro_8088_prod.jed fuse map should be used for production applications.
- Version 1.1
- Recommend using 74F-series, and update the schematic and the silkscreen accordingly. 74F-series ICs are faster and slightly cheaper than 74ALS-series
- Add 74F573 latch for latching A8-A11 signals. This fixes the DMA issue
- Use 74F244 to buffer OSC and CLK signals
- Use AS6C4008 for the second SRAM (U6) instead of AS6C1004. This resolves the AS6C1004 TTL compatibility issue
- Use 74F00 for generating chip select signal for the second SRAM (U6), and for inverting the speaker signal
- Add an optional SPLD (U16) to implement UMBs
- Use 128 KiB Flash ROM instead of 32 KiB EEPROM. It is cheaper, and has twice more storage space
- Use buffered /MEMR and /MEMW signals for SRAM and BIOS ROM
- PCB dimensions changed from 5" x 4.3" to 6" x 4"
- Version 1.0
- Initial version
- Version 1.1
- JP2 description on the back silkscreen suggests that the default JP2 position is Open. Since the recommended chipset is FE2010A and the recommended crystal frequency is 28.63636 MHz, the default JP2 position should be Closed
- Update the silkscreen near ISA bracket mounting holes: The rectangles should be moved to the back silkscreen, and screw head sized circles should be shown on the front skilscreen
- Version 1.0
- System does not boot with NEC V20 CPU.
- This is confirmed to be due to a Phoenix BIOS issue (BIOS image from Intel Wildcard 88)
- Xi 8088 BIOS is currently work in progress, and it doesn't suffer from this issue
- AS6C1008 (U6) does not have TTL compatible inputs causing instability with 640 KiB memory configruation
- Workaround: use CMOS transceiver U11, e.g. 74AHCT245
- DMA doesn't work properly.
- This is due to A8-A11 address lines not beight latched.
- Workaround: add a 74F573 latch, and connect AA8-AA11 and A8-AA11 through it
- System does not boot with NEC V20 CPU.