Replica of a 386SX Mainboard
- V0.1 Initial revision 2022 made with Sprint-Layout
- V0.2 Silkscreen updated, component positions and mounting holes modified
- V0.3 fix 5V bug on J7, add alternative to U6
This replica of a 386SX motherboard is based on the SARC RC2016A chipset. Supported are 386SX or CX486SLC 25/33/40 MHz CPUs. A socket for the optional 80387SX coprocessor is available. The RAM reaches from 512kb to 16MB. I recommend faster 60ns RAM. The manual, jumper settings and useful downloads can be found here https://theretroweb.com/motherboards/s/pcchips-m396f-ver.2.6#downloads
Top view
blank PCB
| Quantity | Description | PCB/Schematic's Reference |
|---|---|---|
| 4 | CAP CER 30 pF RM 5,0 | C11, C13, C36, C38 |
| 3 | CAP CER 47 pF RM 5,0 | C12, C15, C66 |
| 1 | CAP CER 220 pF | CXX (Backside see notice) |
| 1 | CAP CER 4,7 nF RM 5,0 | C16 |
| 1 | CAP CER 100 pF nF RM 5,0 | C65 |
| 10 | CAP CER 100 nF RM 5,0 | C10, C17, C20, C22, C32, C33, C43, C45, C47, C50 |
| 14 | CAP ELKO 10 uF 25V RM 2,5 | C1, C2, C4, C9, C14, C18, C28, C29, C34, C37, C40, C44, C46, C48 |
| 2 | DIODE 1N4148 | D1, D2 |
| 6 | 16 Bit ISA Socket | J2, J3, J4, J5, J6, J7 |
| 1 | AT Power connector | J8 |
| 1 | Battery | BAT |
| 1 | CON 4 PIN | JP1 external Battery |
| 1 | CON 2 PIN | JP2 Display type |
| 1 | CON 5 PIN | JP3 Power LED / Key lock |
| 1 | CON 4 PIN | JP4 Speaker |
| 1 | CON 2 PIN | JP5 Turbo LED |
| 1 | CON 2 PIN | JP6 Turbo switch |
| 1 | CON 2 PIN | JP7 Reset switch |
| 3 | CON 3 PIN | JP8, JP9, JP10 CPU clock select |
| 1 | 3906 | Q1 |
| 2 | 3904 | Q2, Q3 |
| 2 | RES 0 Ohm 5% 1/4W | L1, L2 |
| 2 | RES 22 Ohm 5% 1/4W | R20, R25 |
| 2 | RES 56 Ohm 5% 1/4W | R17, R18 |
| 1 | RES 150 Ohm 5% 1/4W | R27 |
| 1 | RES 220 Ohm 5% 1W | R7 |
| 2 | RES 330 Ohm 5% 1/4W | R13, R28 |
| 3 | RES 470 Ohm 5% 1W | R8, R23, R26 |
| 2 | RES 1 k Ohm 5% 1/4W | R6, R31 |
| 4 | RES 4,7 k Ohm 5% 1/4W | R14, R15, R16, R22 |
| 9 | RES 10 k Ohm 5% 1/4W | R2, R3, R4, R9, R10, R19, R21, R29, R30 |
| 1 | RES 51 k Ohm 5% 1/4W | R5 |
| 2 | RES 1 M Ohm 5% 1/4W | R12, R24 |
| 1 | RES 2 M Ohm 5% 1/4W | R11 |
| 2 | RES Network 4,7 k Ohm bussed | RP1, RP2 |
| 1 | RES Network 330 Ohm bussed | RP3 |
| 3 | RES Network 10 Ohm parallel | RP4, RP5, RP6 |
| 1 | RES Network 100 Ohm parallel | RP7 |
| 1 | IC SARC 6042, VIA VT82C42N, Amikey2, KB-BIOS VER F | U1 |
| 1 | IC 74HC05AP | U2 |
| 1 | IC BIOS | U3 |
| 1 | IC W85C168, MC146818, DS12887, CDP6818E, HM6818 | U4 |
| 1 | IC TC4069UBP | U5 |
| 1 | IC PLL52C05S, TK9107-2, ICW42C07 see U6 note for alternative | U6 |
| 1 | IC CPU | U7 |
| 1 | IC Coprocessor | U8 |
| 1 | IC SARC RC2016A5 | U9 |
| 4 | IC RAM (60ns) | U10, U11, U12, U13 |
| 1 | Quarz 32,768 kHz | X1 |
| 1 | Quarz 14,31818 MHz | X2 |
Backside position CXX (CAP CER 220 pF axial or 0805 SMD)
As an alternative to U6, a DIP-14 crystal oscillator can be used. JP9 and JP10 are not populated for this.
With the DIP-14 oscillator, pin 1 of the oscillator (the sharp edge) is connected to the hole to the left of JP10. Pin 7 of the oscillator is connected to pin 1 of JP9 (ground) and pin 8 (output) is connected to the hole to the right of JP9. Pin 14 of the oscillator (VCC) is connected to pin 3 of JP10.
This board uses the mounting holes marked in green. Modern AT cases often only have the red marked holes.
The project is free for non-commercial reproduktion. Do not sell it on ebay or other platforms for profit. Do not make a closed source. Share your experiences and ideas with the community.