Living in the early 1990s along with the technological advancements in computing and microelectronics was a rewarding experience. Coming from a former communist country where we had no access to technology, let alone latest ones, everything shifted with the beginning of the decade. By chance I had the opportunity to own a very high performance computer for that period. It was an 80386SX based machine running at 25 MHz. Further equipment included 2 Mb RAM, integrated AcuMOS AVGA2 card with 256 K graphics memory, and a 40 Mb Seagate hard disk drive. All packed in a Kenitec desktop case and connected to a 12" AOC monochrome VGA monitor. I discovered modern operating systems, games, and -- drum roll, please -- computer programming. This is the context that marked my life in terms of computers. It changed it completely, shifting my perspective to 180 degrees.
Let's put history aside for a moment and let's concentrate on the motivation. Why would somebody ever attempt to build a vintage computer system? Let alone design one from scratch in 2019? This is over 30 years old technology that is pretty useless now. All period correct computer software can be now run in software emulators on any platform. Mobile phones have tremendous computing power. Tablet computers dominate the mobile market. Then why build such thing? The answer could be very biased. Let's say nostalgia and -- why not? -- because of the engineering challenges. Sure I can buy any 80386DX based mainboard from the big auction site. But it would be better if (sic) I'd built it myself.
Then let's dig into the specifications and my choice of components then.
These are the main specifications of this system design. I have chosen to go with simple approach, using a verified design solution based on OPTi chipset. This reduces the integrated circuit count, power consumption, and connection wiring design errors. Also a smaller ISA card footprint translates into smaller fabrication costs -- which unfortunately are expensive anyway. I tried to stay away from surface mounted parts as much as I could. However the 82C495XLC system control chip comes only in PQFP-160 package. That is a lot of pins to solder.
The schematic that I produced is the result of about one month of sustained work. In order to accomplish this system design, I studied thoroughly the following documents.
However some parts involved in this system design have no datasheet available. I got to know them because I have seen them being used on a lot of period correct mainboards. This calls for reverse engineering as it is the only way I could accomplish the schematic. How I did it? I bought three or four generic 80386DX boards from the local flea market and observed the connections and layout. It was a tedious work and it accounted for most of the time spent designing this microcomputer. I hand-drew all these mini-schematics on paper and analyzed them by comparison to existing designs published in technical literature such as Integrated Circuit Systems Data Book, 1995 edition. And other data books and systems design literature that I have as well. Low-level programming background also helped a lot while working with address and data signals. I don't claim that the produced designs are entirely correct but it is the best I could do. Sometimes I just used my electrical engineering knowledge and engineering common sense to design and interconnect the modules. In the end I have translated everything into a CAD program. Oh, not to mention that I routed all the ~8,400 wires by hand on a four layer printed circuit board. Computer assisted design software has become a serious performer but the human brain far exceeds any existing software to date. At least this is what I like to believe...
So in addition the following work was carried in order to design this microcomputer.
In the end I should say that I have seen a lot of computer hardware over the time and I have also low-level repaired such hardware. Thus I am quite familiar with the x86 architecture.
Some parts of the schematic are optional. The system can run as expected without them. I am thinking here about the Port 80h On-Board Diagnostics section, buffered PC-SPEAKER output circuit, external battery support, 3.6 V LR2032 lithium-ion battery charging circuit, POWERGOOD internal signal generation, PS/2 mouse interface, and some jumpers. Sure the principial schematics can be reduced and the printed circuit board can simply omit these parts. Also jumpers can be hardwired. But I wanted to experiment a little bit so that I can expand my own knowledge.
Sourcing components for this project is not that hard at all. CPU, NPU, OPTi chips, ROM BIOS, and Keyboard controller can be acquired from auction sites. HM8226 and IMI SC425APB as well but you need to be patient to find them. Alternatively you can carefully rescue these from existing (dead, or not) PCBs. Just like I did. ROM BIOS can also be freely downloaded from the Internet and burned into any (EE)PROM integrated circuit of the right organization. You just need to make sure you find the right 80386DX 64K ROM BIOS image. The rest of the components are available at Mouser. I will put a bill of materials (BOM) down below for references. Printed circuit board can be ordered at OSHPark. It is expensive but built quality is high. You will find a link to the project in the BOM below.
This project is work in progress.
Current iteration of ASSY. 2486-SBMC-101 is VER. 1.6 REV. C
I decided to keep it a long time in review so that I can correct all errors and produce the -- expensive -- prototype PCB only once.
* * *
Laudatur ab his, culpatur ab illis. This project is provided as-is and is not for commercial purposes. It reflects my experimental work in microcomputer system design and should be treated as such. I release the schematic and circuit boards to the public for educational purposes. I did all this on my expense and in my free time. So if you like my work, please consider a donation.
Fig. 1: Electrical Principial Schematic
Fig. 2: Top Silkscreen
Fig. 3: Top Layer Printed Circuit Board
Fig. 4: Inner Bottom Layer Printed Circuit Board
Fig. 5: Inner Top Layer Printed Circuit Board
Fig. 6: Bottom Layer Printed Circuit Board
Fig. 7: Top Layer Printed Circuit Board - Simulation
Fig. 8: Bottom Layer Printed Circuit Board - Simulation
The following list contains the parts that are required to assemble this microcomputer.
|80386DX ISA SINGLE BOARD MICROCOMPUTER|
|Printed Circuit Board||ASSY. 2486-SBMC-101||1||VER. 1.6 REV. C||Order from OSHPark|
|IC1-IC4||61C256AH-20||4||256 Kbit SRAM||Order from eBay|
|IC5||61C64AH-20||1||64 Kbit SRAM||Order from eBay|
|IC6||74ACT373||1||Octal 3-state D Latch||595-SN74ACT373N|
|IC7, IC15||74F244||2||Octal 3-state Buffer||595-SN74F244N|
|IC8, IC27||74F08||2||Quad 2-input AND||595-SN74F08N|
|IC9||27C512 80386DX ROM BIOS||1||512 Kbit ROM||556-AT27C512R70PU|
|IC10-IC17||74LS245||7||Octal Bus Transceiver||595-SN74LS245N|
|IC18||74F125||1||Quad 3-state Buffer||595-SN74F125N|
|IC19||74LS32||1||Quad 2-input OR||595-SN74LS32N|
|IC20||74ALS574||1||Octal D Flip-Flop||595-SN74ALS574BN|
|IC22, IC23||DM9368||2||7-segment Decoder||Order from eBay|
|IC24||74LS07||1||Hex Buffer (OC)||595-SN74LS07N|
|IC26||74F32||1||Quad 2-input OR||595-SN74F32N|
|IC28||SC425APB||1||Clock Generator||Order from eBay|
|IC30||VT82C42||1||Keyboard Controller||Order from eBay|
|IC31||HM8226||1||Order from eBay|
|IC32||74LS06||1||Hex Inverter (OC)||595-SN74LS06N|
|IC33||CD4069||1||CMOS Hex Inverter||595-CD4069UBE|
|IC34||OPTi 82C495XLC||1||System Controller||Order from eBay|
|IC35||OPTi 82C206||1||Peripheral Controller||Order from eBay|
|IC36||Intel A80386DX-33 IV||1||CPU||Order from eBay|
|IC37||Intel A80387DX-33||1||NPU||Order from eBay|
|T1||2N3906||1||Small Signal Transistor||512-2N3906BU|
|T2||2N3904||1||Small Signal Transistor||512-2N3904BU|
|T3||2N2222||1||Small Signal Transistor||610-2N2222|
|D1-D6||1N4148||6||Small Signal Diode||78-1N4148|
|C1-C34, C36-C37||100 nF / 50 V||37||MLCC||80-C322C104M5R-TR|
|C35, C38-C39||22 pF / 50 V||3||MLCC||80-C315C220J5G|
|C40-C43||10 pF / 50 V||4||MLCC||80-C315C100J5G|
|C44||471 pF / 50 V||1||MLCC||80-C315C471K5R|
|C45, C71||47 nF / 50 V||2||MLCC||80-C320C473K5R|
|C46, C63-C65||1 uF / 35 V||4||Tantalum Capacitor||80-T350A105K035AT|
|C47-C50, C54-C57||47 pF / 50 V||8||MLCC||80-C315C470J5G|
|C51, C52, C58, C59||56 pF / 50 V||4||MLCC||80-C315C560J5G|
|C53, C60, C66, C68||100 nF / 50 V||4||MLCC||80-C322C104M5R-TR|
|C61, C62||220 pF / 50 V||2||MLCC||80-C315C221K5R|
|C67||2.7 nF / 50 V||1||MLCC||80-C315C272K5R|
|C69, C70||10 uF / 16 V||2||MLCC||810-FK24X5R1C106K|
|C72||220 uF / 6.3 V||1||Polymer Capacitor||80-A758BG227M0JAAE18|
|C73||10 uF / 25 V||1||Tantalum Capacitor||80-T350E106M025AT|
|C74||100 pF / 50 V||1||MLCC||80-C315C101K5R|
|C75-C80||10 uF / 25 V||6||Tantalum Capacitor||80-T350E106M025AT|
|R1, R19||100 Ω||1||Carbon Resistor||291-100-RC|
|R2, R28, R29, R31, R38||1 kΩ||5||Carbon Resistor||291-1K-RC|
|R3, R5||10 kΩ||2||Carbon Resistor||291-10K-RC|
|R4||51 kΩ||1||Carbon Resistor||291-51K-RC|
|R6||2 MΩ||1||Carbon Resistor||291-2M-RC|
|R7, R8, R36||470 Ω||3||Carbon Resistor||291-470-RC|
|R9, R10, R15||150 Ω||3||Carbon Resistor||291-150-RC|
|R11-R14||22 Ω||4||Carbon Resistor||291-22-RC|
|R16, R17, R20, R22||330 Ω||4||Carbon Resistor||291-330-RC|
|R18, R23||33 Ω||2||Carbon Resistor||291-33-RC|
|R21||200 kΩ||1||Carbon Resistor||291-200K-RC|
|R24||2.2 kΩ||1||Carbon Resistor||291-2.2K-RC|
|R25||47 kΩ||1||Carbon Resistor||291-47K-RC|
|R26, R37||4.7 kΩ||2||Carbon Resistor||291-4.7K-RC|
|R27||10 kΩ||1||Trimmer Resistor||72-T7RYA103KT20|
|R30||51 Ω||1||Carbon Resistor||291-51-RC|
|R32-R35, R39-R41, R43||330 Ω||8||Carbon Resistor||291-330-RC|
|RN1-RN5||9 x 4.7 kΩ||5||Bussed Resistor Network||652-4610X-1LF-4.7K|
|RN6||9 x 1 kΩ||1||Bussed Resistor Network||652-4610X-1LF-1K|
|RN7, RN8||7 x 2.2 kΩ||2||Bussed Resistor Network||652-4608X-1LF-2.2K|
|RN9-RN11||7 x 4.7 kΩ||3||Bussed Resistor Network||652-4608X-1LF-4.7K|
|RN12||4 x 4.7 kΩ||1||Bussed Resistor Network||652-4605X-1LF-4.7K|
|RA1-RA5||4 x 22 Ω||5||Resistor Array||652-4608X-2LF-22|
|X1||14.31818 MHz Crystal||1||Quartz Crystal||73-XT49S1431-20|
|X2||32.768 kHz Crystal||1||Quartz Crystal||520-TFC3X8-X|
|DISP1, DISP2||RFT VQB37||2||Common Cathode||Order from eBay|
|LED1||5 mm Green LED||1||Power Indicator||755-SLR-56MC3F|
|LED2||5 mm Orange LED||1||Turbo Indicator||755-SLR-56DC3F|
|IC Socket||20-pin||12||IC6, IC7, IC20, IC21, IC10-IC17||575-193320|
|IC Socket||14-pin||10||IC8, IC18, IC19, IC24-IC28, IC32, IC33||575-193314|
|IC Socket||8-pin||2||IC29, IC31||575-193308|
|SIMM Socket||30-pin||8||SIMM1-SIMM8||Order from eBay|
|SPK1||Electromagnetic Speaker||1||85 dBA||665-AT-1224TWTR|
|JP1, JP4-JP7, JP11||2-pin Header||6||Jumper||649-68001-202HLF|
|JP2, JP3, JP8-JP10||3-pin Header||5||Jumper||649-68001-203HLF|
|J3, J10||4-pin Header||2||Header||649-68001-204HLF|
|J4-J7, J9, J11||2-pin Header||6||Header||649-68001-202HLF|
|J1||6-pin Mini DIN Connector||1||PS/2 Keyboard||571-5749265-1|
|J2||6-pin Mini DIN Connector||1||PS/2 Mouse||571-5749265-1|
|ISA Card Bracket||Custom Built||1||3D Printed||N/A|
Here is a list of things you need to pay attention to should you decide to build such ISA system backplane.
This microcomputer is PC AT compatible by all means. That means all software written originally for the PC AT platform will be fully compatible with this system. Think MS-DOS, Microsoft Windows, and DOS games. You can run Unix-class operating systems as well. For this reason I had to follow closely the PC AT architecture during the system design process.
The system block diagram allows for a better understanding of the principle of operation.
Fig. 1: System Block Diagram
The microcomputer is controlled by the OPTi 82C495XLC system controller integrated circuit. This chip has the following features.
Additional mainboard logic is carried by the OPTi 82C206 integrated peripheral controller. This chip handles the following functions.
PS/2 keyboard and mouse are carried by the VT82C42 chip. This is vastly superior to original 8042-class microcontrollers with embedded software. The VIA chip includes hardware logic for very fast decoding of keyboard and mouse commands.
To simplify a little bit the operation of this microcomputer, we can sum it up simply as follows.
Following are described all the interface connectors and their respective pinouts.
|INTERFACE CONNECTORS DESCRIPTION|
|J1||PS/2 Keyboard||1 - Keyboard Data|
2 - NC
3 - Ground
4 - +5 V
5 - Keyboard Clock
6 - NC
|J2||PS/2 Mouse||1 - Mouse Data|
2 - NC
3 - Ground
4 - +5 V
5 - Mouse Clock
6 - NC
|J3||External Battery||6 V Battery Pack||1 - +6 V|
2 - NC
3 - Ground
4 - Ground
|J4||Reset Switch||1 - Reset Signal|
2 - Ground
|J5||Turbo Switch||1 - Turbo Signal|
2 - Ground
|J6||Turbo LED||1 - LED Anode|
2 - LED Cathode
|J7||Power LED||1 - LED Anode|
2 - LED Cathode
|J8||Keyboard Lock||1 - Ground|
2 - Keyboard Lock Signal
3 - Ground
|J9||Power Good||200 msec Delayed +5 V Signal||1 - Power Good Signal|
2 - Ground
|J10||PC Speaker||1 - Speaker Data Output|
2 - Internal Speaker Data Output
3 - Ground
4 - +5 V
|J11||Amplified PC Speaker||Connect to Sound Card Line-In||1 - Ground|
2 - Audio Signal
The Power Good signal is used to let the board know that the power supply rails have reached operating voltages and amperages. Normally this is provided by all AT class power supplies on pin 1 of the mainboard power supply connector. Since this board is going to be powered directly from the ISA bus, there is absolutely no knowledge about this signal. Thus I designed a simple RC circuit to emulate it while also providing an option to connect to an external Power Good signal through J9. It is very unlikely that you will find an ISA system backplane that will have a Power Good signal header. But I have provided it anyway. However the internal RC circuit will provide the required 200 msec delayed +5 V signal that will initialize the on-board logic. So normally connect jumper to JP3 pins 1-2.
My original PC back in 1993 was equipped only with a PC Speaker. Thus I have experimented all games only with PC Speaker sound. As much as I hate or love it, I have provided some extra PC Speaker configuration options for nostalgia reasons. So there are four PC Speaker modes as follows.
Historical Note: I always liked the PC Speaker soundtrack of the Konami Knightmare game ported by Todor Todorov to MS-DOS. But there was no way to turn up or down the volume. And there is the original Duke Nukem (DN1, DN2, and DN3) which I always would have liked to have the ability to turn down the volume for. Playing without sound effects was no fun and with sound effects was disturbing for the other people in the house.
As soon as the PC will perform the power on self-tests (POST) the BIOS will start to put human readable hexadecimal codes on hardware port 0x80h. This is very useful for debugging purposes should the PC freeze during the initialization procedure. In order to catch these codes a simple circuit based on an octal flip-flop and two 4-bit BCD to 7-segment decoders. During POST, hexadecimal codes will be displayed with very high speed. But in case the computer freezes, the last code remains visible on the two displays.
The decimal points of the two displays are hardwired as reset indicator. Thus while you press the reset button or if the hardware is in initialization mode -- Power Good signal is not yet active -- the H elements of the two displays will be lit.
Note: There is software out there in the wild that will perform casual writes to port 0x80h. This was a normal behavior for software programmers since they could do several tricks such as adding small delays in programs. So you might see different messages displayed during normal operation of several computer programs. However these do not represent diagnostic codes and can be safely ignored.
I have provided some basic system configuration options under the form of jumpers. The star (*) symbol signifies the default option.
|JP1||BATT||Internal Battery Charge||CL: Charge|
OP: Normal (*)
|JP2||CMOS||NVRAM Status||1-2: Clear|
2-3: Normal (*)
|JP3||POWERGOOD||Power Good Signal Source||1-2: Internal (*)|
|JP4||MONITOR||Monitor Type||CL: Monochrome|
OP: Color (*)
|JP5, JP6, JP7||CPU CLK||80386DX Clock||CL, OP, OP: 25 MHz|
OP, CL, OP: 33 MHz (*)
OP, CL, CL: 40 MHz
|JP8||NPU CLK||80387DX Clock Type||1-2: Buffered (*)|
|JP9||NPU RST||80387DX Reset Signal||1-2: Software Port 0xF1h|
2-3: Synchronous with 80386DX (*)
|JP10||IRQ12||IRQ12 Routing||1-2: ISA BUS|
2-3: PS/2 Mouse (*)
|JP11||TMRCLK||PIC Timers Clock Signal||CL: Always|
OP: On Request (/XIOW Signal) (*)
This microcomputer is equipped with dynamic random access memory (DRAM) under the form of eight SIMMs.
|SYSTEM DRAM CONFIGURATION|
|RAM Size||BANK #0||BANK #1||Notes|
|1 MB||4 x (256 K x 9)||Empty|
|2 MB||4 x (256 K x 9)||4 x (256 K x 9)|
|4 MB||4 x (1 M x 9)||Empty|
|5 MB||4 x (256 K x 9)||4 x (1 M x 9)|
|5 MB||4 x (1 M x 9)||4 x (256 K x 9)|
|8 MB||4 x (1 M x 9)||4 x (1 M x 9)|
|16 MB||4 x (4 M x 9)||Empty|
|20 MB||4 x (1 M x 9)||4 x (4 M x 9)|
|20 MB||4 x (4 M x 9)||4 x (1 M x 9)|
|32 MB||4 x (4 M x 9)||4 x (4 M x 9)||Entirely Cached|
The main memory is entirely cached for faster access. System cache static random access memory (SRAM) organization is described in the following table.
|SYSTEM CACHE SRAM CONFIGURATION|
|Cache Size||Tag SRAM Size||Cache SRAM Size||Cacheable RAM Size|
|128 KB||1 x (8 K x 8)||4 x (32 K x 8)||32 MB|
Memory speed requirements are listed below.
|MEMORY SPEED REQUIREMENTS|
|CPU||Tag SRAM||Cache SRAM||DRAM|
|33 MHz||15 ns||20 ns (R/W: 1 WS)||80 ns (R/W: 0 WS)|
OPTi 82C206 emulates two Intel 8259A interrupt controllers in a master-slave configuration. Thus a maximum of 16 interrupt requests are available for system hardware. The IRQ map is listed below.
|IRQ Channel||PIC||Map||Other Uses|
|IRQ3||Master||Free||COM2 and COM4|
|IRQ4||Master||Free||COM1 and COM3|
|IRQ5||Master||Free||LPT2 and LPT3, Sound Card|
|IRQ6||Master||Free||Floppy Disk Controller|
|IRQ7||Master||Free||LPT1, Sound Card|
|IRQ8||Slave||Real-Time Clock (RTC)||N/A|
|IRQ9||Slave||IRQ2||IRQ2 maps to IRQ9|
|IRQ10||Slave||Free||SCSI, NIC, T. IDE Channel|
|IRQ11||Slave||Free||SCSI, NIC, Q. IDE Channel|
|IRQ13||Slave||Numeric Processor (NPU)||N/A|
|IRQ14||Slave||Free||Primary IDE Channel|
|IRQ15||Slave||Free||Secondary IDE Channel|
Notes on IDE interface IRQ mapping as follows.
OPTi 82C206 emulates two Intel 8237 direct memory access (DMA) controllers in a master-slave configuration. Thus a maximum of 7 DMA channels are available for system hardware. The DMA map is listed below.
|DMA Channel||Bus Type||Transfers||Map/Other Uses|
|DMA1||8/16-bit||8-bit||Sound Card, SCSI|
|DMA2||8/16-bit||8-bit||Floppy Disk Controller|
|DMA3||8/16-bit||8-bit||LPT1 (ECP Mode)|
|DMA4||N/A||16-bit||DMA Controller Cascade|
|DMA5||16-bit||16-bit||Sound Card, SCSI|
|DMA7||16-bit||16-bit||Sound Card, SCSI|
For the sake of completeness I am adding here the standard I/O address ranges of various ISA peripherals that can be part of a PC/AT-class microcomputer. Although the I/O address ranges could be wildly varied for exotic ISA cards, most of the dedicated hardware has well known addresses which are assigned as follows.
|I/O ADDRESS RANGE|
|0x168h||Quaternary IDE Channel|
|0x170h||Secondary IDE Channel|
|0x1E8h||Tertiary IDE Channel|
|0x1F0h||Primary IDE Channel|
|0x278h||LPT2 or LPT3 using IRQ5|
|0x280h||NIC, LCD Display I/O|
|0x2E8h||COM4 using IRQ3|
|0x2F8h||COM2 using IRQ3|
|0x320h||SCSI, NIC, ESDI Hard Disk Drive Interface|
|0x330h||SCSI, MPU-401 MIDI Interface|
|0x378h||LPT1 using IRQ7 in Color Systems|
|0x388h||FM Sound Synthesis|
|0x3BCh||LPT1 using IRQ7 in Monochrome Systems|
|0x3E8h||COM3 using IRQ4|
|0x3F8h||COM1 using IRQ4|
|0x678h||LPT2 or LPT3 Extended Parallel Port (EPP) using 0x278h|
|0x778h||LPT1 Extended Parallel Port (EPP) using 0x378h (Color Systems)|
|0x7BCh||LPT1 Extended Parallel Port (EPP) using 0x3BCh (Monochrome Systems)|
I have rescued this original AMIBIOS ROM integrated circuit from a working generic 80386DX / 40 MHz mainboard. Before I removed it from the board, I dumped its contents as a .BIN file which you can download. You need to program a 27C512 or a 28C512 (E)EPROM integrated circuit with this binary image in order to use the microcomputer. I don't know whether other BIOS types will work or not with this board, but this one does. I think mostly because the mainboard was based on the OPTi 82C495XLC system controller chip -- which I have also rescued for this project. The BIOS string identifies a Jetway branded mainboard but there is no visual identification or code on the printed circuit board to back-up this hypothesis. However I have seen a bunch of similar -- read: near identical -- mainboards with minimal layout differences; all unbranded. The attack of the clones, perhaps?
BIOS File: 80386DX.BIN
BIOS String: X0-0803-001276-00101111-080893-OP495XLC-H
While this BIOS image is created by American Megatrends Inc. (AMI), it would have been really fun if I had the time to program my own version of the BIOS but unfortunately it is not possible at this moment. But if you'd like to, please open a GitHub repository where collective effort could be helpful. I will surely put a link to that repository on this page.
An adapter can be build in order to replace the International Microcircuits Incorporated (IMI) SC425APB master clock generator integrated circuit. However in order to provide full functionality on changing CPU frequencies by means of the JP5, JP6, and JP7 jumpers, the circuit becomes a little bit complicated. For the sake of simplicity I will describe a replacement circuit locked for 33 MHz CPU clock. In this case, the CPU frequency selector jumpers become useless.
So the adapter circuit needs to provide three main frequencies as follows.
The adapter circuit to SC425APB IC socket pin mapping needs to be done according to the following description.
This circuit can be made very compact in SMD technology. The 74F74 D-type dual flip-flop can be replaced by the SN74LVC1G74 single D-type flip-flop integrated circuit. 74F04 hex inverter can be replaced by SN74LVC3GU04 triple inverter. With a little bit of tweaking around you can build this adapter under the form of a DIP-14 PCB to insert directly in the SC425APB socket.
Because my searches for a compatible ISA bracket were not that successful and because this is an entirely DIY project, I decided to attempt to build one myself. While I do have some experience with AutoCAD, I haven't used this computer program since 2006. Thus I decided to try a different approach for the sake of learning something new. So I went with OpenSCAD this time.
However, the ISA bracket is work in progress at this moment.
TO BE CONTINUED SOON At the moment I am waiting for the PCB to arrive from the Factory.
Copyright © 2004- Alexandru Groza
All rights reserved.
VER. 1.0 | REV. A