This is an IBM XT-compatible CPU and RTC card, based on a design by Sergey Kiselev and Aitor Gómez García.
The goal of this project is to create an XT-compatible computer on a passive backplane with a modular card-based architecture, minimizing the overall footprint while providing support for all common expansion cards.
Schematic PDF: Schematic - Version 1.0
PCB PDF: Board Design - Version 1.0
Gerber Files: Gerber- Version 1.0
SPLD:
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U16 CPU-Part: Use the repository provided by Sergey Kiselev
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U17 RTC-Part: Use the repository provided by Sergey Kiselev
AT2XT Firmware:
| Component type | Reference | Description | Quantity |
|---|---|---|---|
| PCB | Micro 8080 + RTC PCB | 1 | |
| Integrated Circuit | U1 | Intel 8088, 80C88, or NEC V20 CPU | 1 |
| Integrated Circuit | U2 | Intel 8087 FPU | 1 |
| Integrated Circuit | U3 | Faraday FE2010A | 1 |
| Integrated Circuit | U4 | SST39SF010A Flash ROM, DIP-32 package | 1 |
| Integrated Circuit | U5, U6 | AS6C4008 SRAM, DIP-32 package | 2 |
| Integrated Circuit | U7 - U9 | 74F573 Octal D-Type Latch | 3 |
| Integrated Circuit | U10, U11 | 74F245 Octal Bus Transceiver | 2 |
| Integrated Circuit | U12, U13 | 74F244 Octal Buffer | 2 |
| Integrated Circuit | U14 | 74F00 Quad 2-Input NAND Gate | 1 |
| Integrated Circuit | U15 | PIC12F629 Microcontroller | 1 |
| Integrated Circuit | U16 | ATF16V8B SPLD | 1 |
| IC Socket | U1, U2 | DIP-40, 600 mil socket | 2 |
| IC Socket | U3 | PLCC-84 through hole socket | 1 |
| IC Socket | U4-U6 | DIP-32, 600 mil socket | 3 |
| IC Socket | U7-U13, U16, U17 | DIP-20, 300 mil socket | 9 |
| IC Socket | U14 | DIP-14, 300 mil socket | 1 |
| IC Socket | U15 | DIP-8, 300 mil socket | 1 |
| IC Socket | U18 | DIP-24, 600 mil socket | 1 |
| Diode | D1 | 1N4148 | 1 |
| LED | D2 | 3 mm, green LED indicator | 1 |
| Transistor | Q1 | PN2222A, 2.54mm lead spacing | 1 |
| Crystal | X1 | 28.63636 MHz, 18 pF, HC-49/S | 1 |
| Crystal | X2 | 32768Hz | 1 |
| Battery | BT1 | Battery socket | 1 |
| Speaker | SP1 | 12 mm speaker | 1 |
| Tactile Button | SW1 | 6 mm tactile button, right angle | 1 |
| DIP Switch | SW2, SW3 | 3 positions | 2 |
| DIP Switch | SW4 | 5 positions | 1 |
| Connector | P1 | 6 pin Mini DIN, purple | 1 |
| Pin Header | P2 | 4 pin header, 2.54 mm pitch | 1 |
| Pin Header | P3, JP1-JP5 | 2 pin header, 2.54 mm pitch | 6 |
| Capacitor | C1 - C18 | 0.1 uF, MLCC, 5 mm lead spacing | 19 |
| Capacitor | C18 - C20 | 10 uF, MLCC, 5 mm lead spacing | 3 |
| Trimmer Capacitor | C21 | 6.5-30 pF, 5 mm lead spacing | 1 |
| Capacitor | C22 | 47 pF, MLCC, 5 mm lead spacing | 1 |
| Capacitor | C23 | 0.01 uF, MLCC, 5 mm lead spacing | 1 |
| Resistor Array | RR1 | 4.7 k, bussed, 10 pin SIP | 1 |
| Resistor Array | RR2 | 10 k, bussed, 10 pin SIP | 1 |
| Resistor Array | RR3, RR4 | 4.7 k, bussed, 6 pin SIP | 2 |
| Resistor Array | RR5, RR6 | 10 k, bussed, 6 pin SIP | 2 |
| Resistor | R1 | 33 ohm, through hole | 1 |
| Resistor | R2, R3 | 47 ohm, through hole | 2 |
| Resistor | R4, R5 | 470 ohm, through hole | 2 |
| Resistor | R6 | 1 kohm, through hole | 1 |
| Resistor | R7 | 10 kohm, through hole | 1 |
| Resistor | R8 | 1 Mohm, through hole | 1 |
| Fuse | F1 | 1.1A polyfuse, 5.08 mm lead pitch | 1 |
| ISA Bracket | Keystone Electronics 9202 | 1 | |
| Screw | 4-40 x 1/4" Screw | 2 |
- Initial Release
- Install either U14 or U16, not both together
- The card is still in the testing phase.
- This card won't fit Sergey's case (this one). The case will need to be enlarged.
- Card size 185.3 mm x 102.9 mm