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rehsd
Nov 26, 20236 min read
486DLC >>> 486DX PCB Design Updates
As I have gotten my 386 DX upper and lower motherboard PCBs working -- at least to the point of validating much of the design -- I am now...
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rehsd
Oct 8, 20231 min read
386 DX - EATX Build
Picking up from 80386 DX Build (rehsdonline.com), I am transitioning my 386 DX build to an EATX form factor, incorporating changes up to...
210 views0 comments
rehsd
Jul 8, 20234 min read
386SX Upgrade / 386DX - Glue Logic, Bus Control PALs, GALs, PLDs, ...
For my 286 to 386SX upgrade interposer PCB, I need to implement logic for S0# and S1# (along with a few other signals). For my 386DX...
249 views2 comments
rehsd
Jun 19, 20232 min read
80386 DX Build
While I continue to build out my 286 (386 SX) system, I thought I would start learning more about the 80386 DX. I am hoping to have a...
571 views0 comments
rehsd
Jun 15, 20232 min read
386SX Upgrade
I'm looking into a 386SX upgrade for my 286 build. The Intel 386 Hardware Reference Manual includes the following schematic for...
734 views2 comments
rehsd
Jun 13, 20232 min read
Accessing More RAM
I am researching how to add additional RAM to my 286 build. I started by thinking about a memory expansion card for my system. That has...
133 views0 comments
rehsd
Jun 12, 20231 min read
FreeDOS Running. Lots More Work Needed.
I now have FreeDOS running on my 286 build. In this running post, I'll add information about incremental updates I am doing. In the...
61 views0 comments
rehsd
Jun 5, 20231 min read
80286 System Roadmap (updated June 2023)
Back in January of this year, I posted a list of potential roadmap items for my 26 build. See 80286 System Roadmap (rehsdonline.com). As...
108 views0 comments
rehsd
May 4, 20235 min read
Troubleshooting FreeDOS Boot on my 286 System - Hangs on execrh() Call in Kernel
As I continue to work towards getting FreeDOS running on my 286 homebrew build, I am encountering a new issue. During boot, the FreeDOS...
186 views2 comments
rehsd
Apr 30, 20233 min read
Troubleshooting CPU Flags Register Between BIOS and FreeDOS
I am running into an issue getting expected CPU flags register values back from interrupt calls made in FreeDOS to my BIOS on my 286...
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rehsd
Apr 17, 20235 min read
FreeDOS Development Environment
In this post, I will share a bit about the development environment I am using to build FreeDOS (and possibly other DOS applications). I...
173 views2 comments
rehsd
Apr 16, 20233 min read
Booting FreeDOS
At this stage of my homebrew 286 system build, I have an IDE interface to a compact flash (CF) card. I have begun implementing disk...
123 views2 comments
rehsd
Apr 14, 20231 min read
IDE Interface
I am currently working to see if I can boot to an IDE storage device (specifically, a CF Card) and get FreeDOS's kernel loaded. I'll use...
97 views0 comments
rehsd
Apr 2, 20231 min read
286 Build - Six Months In
I am nearly six months into my 286 project. While I started on breadboards, I am now at a nice stage where I have an ATX form-factor...
226 views0 comments
rehsd
Mar 10, 20231 min read
Interrupts and More Interrupts
I am starting to implement support for additional interrupts on my 286 system. This includes BIOS interrupts and DOS interrupts. Relevant...
100 views0 comments
rehsd
Feb 24, 20235 min read
Using C/C++ with my 286
Up to this point, all code running on my 286 system has been x86 assembly (real mode). I am hoping to learn how to compile C or C++ code...
185 views3 comments
rehsd
Feb 20, 20232 min read
286: Onboard ROM Updates
A helpful feature that I am looking to add to my 286 system is onboard flash ROM updates, where I do not need to remove the flash ROMs to...
90 views0 comments
rehsd
Feb 17, 20231 min read
Sound Card for my 286 System
For my sound card, I plan to leverage previous work that I did for my 65816 system build. I will refactor the sound card to support my...
2,226 views0 comments
rehsd
Feb 15, 20232 min read
Mouse for my 80286 System (SPI to PS/2)
My 286 system does not have built-in mouse support (yet). I have been experimenting with a few options. Back on my 6502 system, I added...
45 views0 comments
rehsd
Jan 25, 20233 min read
80286 System Roadmap
Last October (2022), I started my learning journey to develop a 286 system. See Start to an 80286 System. As of this writing, I have a...
221 views3 comments
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