This board write up is still very much a work in progress.

### Introduction

David Conroy over at http://www.fpgaretrocomputing.org/pdp10x has created a (customized) PDP10-on-FPGA system which he calls the PDP-10/X, and has extensively documented his work on that site. In October 2018, he made an archive of the development environment of this system available to a member of the RetroBrewComputers.org community, who posted that archive here: https://www.retrobrewcomputers.org/forum/index.php?t=msg&th=333

In that thread, there were efforts to use some of Conroy's existing boards and to use newly manufactured boards to create a working system. However, both approaches required soldering a 208-pin 0.5mm pitch TQFP package for the FPGA, which is challenging to say the least.

I noticed that the same FPGA, a Xilinx Spartan 3E, was available as a development board from WaveShare.com, so no SMT soldering required. (They make the same board available on eBay and AliExpress). After checking that enough pins were available on the FPGA board, I set out to create a new system board in KiCad. I eventually got that redesign of the system board to work, and posted my results in that thread.

I decided that since the FPGA is a bit expensive ($35), the board could stand to have more utility than just running Conroy's PDP-10/X, so I added the parts needed to run a Multicomp system to get to the board described here. ### Features • Supports the WaveShare Core3S500E board, which contains a Xilinx Spartan 3E with about 500K logic elements (LE), about 45K on board SRAM, and 116 I/O pins. The board is designed to be pin compatible with other WaveShare FPGA boards, including some of the Altera ones, but I have not used one of those yet. • 2.5 MB of SRAM (5x 512KB by 8 SRAM chips) • 4MB of Serial EEPROM, used by the PDP-10/X (could be supported by Multicomp but currently is not). • TTL 6-pin Serial port (used by both PDP-10/X and Multicomp) • DS1337 I2C Real Time Clock, with coin-cell battery backup (PDP-10/X support only) • 40-pin IDE port (PDP-10/X support only, can be used as general GPIO in a Multicomp system) • WizNet Ethernet support (PDP-10/X only) • VGA, PS/2 (5V & 3.3V) and SD card interfaces (Multicomp only) The board uses a standard 5V/2A wall-wart DC power supply with a 5.5mmx2.1mm connector jack. ### Schematics and Build Files My board, schematics, layout files and code changes are made available under the Creative Commons BY-SA-NC 4.0 license. Item File Schematics pdp10x_v01_schematic.pdf Manufacturing Files (Gerbers) pdp10x_v01.zip KiCad Files On GitLab: pdp10x_system_board ### Acknowledgements and Licenses For the PDP-10X, thanks to David Conroy for making his extensive work available. I've simply reimplemented his System Board in KiCad and added some Multicomp compatibiilty. But all of the Verilog to implement the PDP-10/X is his work. For Multicomp, thanks to Grant Searle for making the original system available. His work was published with the following license: “By downloading these files you must agree to the following: The original copyright owners of ROM contents are respectfully acknowledged. Use of the contents of any file within your own projects is permitted freely, but any publishing of material containing whole or part of any file distributed here, or derived from the work that I have done here will contain an acknowledgement back to myself, Grant Searle, and a link back to this page. Any file published or distributed that contains all or part of any file from this page must be made available free of charge.” http://searle.x10host.com/Multicomp/index.html, retrieved 01/27/2020. Thanks to Rienk Koolstra (rhkoolstar) for his useful extensions to the Z80 Multicomp (MC-2G-1024) system. He also provided me a PS/2 connector footprint when I could not find a decent one. Thanks to Jose Luis Collado (positron) for his work in porting Multicomp to the Xilinx-based Papilio Duo board. I've reused some of that work here. (If there is no license mentioned for the above works, it's because I could not find one. Please send corrections.) ### Bill of Materials (BOM) There are a few items that can't or shouldn't be purchased from the usual electonic part distributors (unavailable or too expensive): • SPI ROM Programmer. The usual MiniPRO TL866CS works fine. • 2x “2mm Pitch 2×30 Pin 60 Pin Female Double Row Straight Pin Header Strip.” Expensive at the usual distributors, so find on Ebay/AliExpress using this quoted search term. • A 5V, 2A, 5.5mm x 2.1mm regulated DC power supply (wall wart). Very common, buy at your favorite supplier. • A 6-32 screw and nut for the LM1086 voltage regulator. • [Multicomp] A microSD breakout board. Search Ebay/AliExpress for “arduino mini microsd module.” Try to find one without the header pins attached. If you get one with headers attached, you'll need to remove (desolder) the pins that come on the board. • [Multicomp] A 1 GB or greater microSD card (SDHC). • [PDP-10/X] A 256 MB or greater compact flash card, and some way to get a disk image onto the flash card. The rest of the BOM is listed in the table below. Here is text file that you can copy & paste in to Mouser's BOM tool. After you add the BOM to Mouser's cart, be sure to carefully review your the parts list and remove parts you already have or are getting elsewhere. Reference Quantity Item Description Mouser Part No. C101, C102, C601 3 10uF Tantalum Capacitors - Solid Leaded 25V 10uF 10% ESR=2.5 Ohms 581-TAP106K025SCS C301, C501-C505, C602 7 0.1uF Multilayer Ceramic Capacitors MLCC - Leaded 0.1uF 50volts 10% X7R 5mm LS 594-K104K15X7RF53H5 D601, D602 2 1N4148 Diodes - General Purpose, Power, Switching 100V Io/200mA BULK 512-1N4148 J1 1 Barrel_Jack DC Power Connectors Power Jacks 490-PJ-002A J101, J102 2 Conn_02x30_Odd_Even Headers & Wire Housings 2.00 mm FleXYZ Cost-effective Tiger Buy Square Tail Socket Strip 200-SQT13001FD (much cheaper on eBay/AliExpress) J103 1 Conn_02x16_Odd_Even Headers & Wire Housings 32P DR STRT RECPT 2MM LEAD LENGTH 798-A3C-32DA-2DSC71 J104 1 Conn_02x12_Odd_Even Connector_PinHeader_2.54mm:PinHeader_2x12_P2.54mm_Vertical 649-67997-272HLF J3, J105 2 Conn_01x06 Connector_PinHeader_2.54mm:PinHeader_1x06_P2.54mm_Vertical 538-42375-1855 J201 1 Conn_02x20_Odd_Even Headers & Wire Housings 40P R/A SOLDER TAIL HIGH TEMP 517-N2540-5002RB J901, J902 2 Conn_02x14_Odd_Even Connector_PinSocket_2.54mm:PinSocket_2x14_P2.54mm_Vertical 649-67997-272HLF J903 1 DB15_Female_HighDensity D-Sub High Density Connectors RA 15POS FEM Steel 636-193-015-213R531 J904 1 Mini-DIN-6 DIN Connectors Mini Din Connectors 490-MD-60SM JP201 1 Jumper Connector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_Vertical 538-42375-1855 Q901, Q902 2 2N7000 MOSFET N-CHANNEL 60V 200mA 512-2N7000 R301, R302, R303, R313, R314,R501-R504,R803,R804,R901,R909-R913 17 10K ohm resistor Carbon Film Resistors - Through Hole 10Kohm 5% 1/4W 603-CFR25SJT-52-10K R305, R306 2 220 ohm resistor Carbon Film Resistors - Through Hole 220ohm 5% 1/4W 603-CFR-25JT-52-220R R401-R425 25 33 ohm resistor Carbon Film Resistors - Through Hole 33 Ohm 5%TR 1/4W 603-CFR-25JR-5233R R601, R801, R802 3 1K ohm resistor Carbon Film Resistors - Through Hole 1/4W 1K Ohm 1% 603-CFR-25JT-52-1K R602, R603 2 1.8K ohm resistor Carbon Film Resistors - Through Hole 1.8K ohm 1/4W 5% 603-CFR-25JR-521K8 R805, R902 2 560 ohm resistor Carbon Film Resistors - Through Hole 1/4W 560 Ohm 5% 603-CFR-25JR-52-560R R903, R905, R907 3 680 ohm resistor Carbon Film Resistors - Through Hole 680 OHM 2% 1/4W 660-CFS1/4CT52R681G R904, R906, R908 3 470 ohm resistor Carbon Film Resistors - Through Hole 470 OHM 2% 1/4 660-CFS1/4CT52R471G U1 1 LT1086-3.3 LDO Voltage Regulators 3.3V Low Dropout Pos VR 1.5A 584-LT1086CT-3.3#PBF U301 1 W25Q32JV NOR Flash spiFlash, 32M-bit, DTR, 4Kb Uniform Sector 454-W25Q32JVDAIQ U501-U505 5 AS6C4008-55PCN SRAM 4M, 2.7-5.5V, 55ns 512K x 8 Asynch SRAM 913-AS6C4008-55PCN U601 1 DS1337 Real Time Clock IC Serial Real-Time Clock 700-DS1337 U901 1 74LS244 Buffers & Line Drivers Tri-State Octal 595-SN74LS244N X301,X601 2 8 pin DIP Socket IC & Component Sockets 8P TIN PIN TIN CNT 575-144308 X501-X505 5 32 Pin DIP Socket IC & Component Sockets 32P TIN PIN TIN CONT 575-1144632 X901 1 20 pin DIP Socket IC & Component Sockets 20P TIN PIN TIN CONT 575-199320 Y601 1 32.768 kHz Crystals 32.768KHz10ppm 6pF 695-CFS-20632768EZBB A901 1 WIZ830MJ WIZ830MJ: Networking Modules W5300+MAG JACK 950-WIZ830MJ ($25 at Mouser)
BT601 1 CR3032 Coin Cell Battery 3V 30 X 3.2 MM 500mA 658-CR3032
X601 1 Battery_Cell Coin Cell Battery Holders 20MM VERT SLIMLINE 534-1065
To be continued…