- HP 6235A Power Supply Rebuild 2024 MAR 28 in test_equipment
- YES-100 32K Static RAM Board 2024 MAR 25 in s100
- Superboard II Repair 2024 MAR 24 in osi
- CD-23 Disk System Repair Part 2 2024 JAN 29 in osi
- HP 10544A Ovenized Oscillator Teardown and Repair 2023 DEC 20 in test_equipment
- HP 5326B Counter Repair 2023 DEC 17 in test_equipment
- CD-23 Disk System Repair Part 1 2023 JUL 26 in osi
- System Interface for 8085 SBC rev 1 2023 JUL 20 in i8085
- 8085 SBC rev 1 Reprise 2023 JUL 19 in i8085
- MTU Visable Memory Repair 2023 APR 05 in vintage-misc
- Certek SBC85-2 Control Computer 2023 MAR 21 in i8085
- General Radio 1192B Counter 2023 MAR 14 in test_equipment
- Pegasus II Repair 2023 FEB 25 in s100
- Cleaning DEC RL Packs 2023 FEB 23 in dec
- Gralex Panel Meter 2023 FEB 18 in test_equipment
- Krohn-Hite 5100B Function Generator 2023 FEB 13 in test_equipment
- Homebrew Counter with Nixie Tubes 2023 FEB 12 in test_equipment
- HP 59304A Numeric Display 2023 FEB 11 in test_equipment
- Sun 511 SCSI Shoebox 2023 JAN 30 in sun
- Sun 19 Inch ECL Monitor Cleanup 2022 DEC 31 in sun
- Ampro Series 100 Repair 2022 NOV 30 in vintage-misc
- Repairing an Unexpanded Altair 8800 2022 NOV 02 in s100
- Shiva LanRover/E PLUS 2022 OCT 28 in vintage-misc
- VA Linux FullOn 2x2 Server Cleanup 2022 OCT 27 in vintage-misc
- DEC Scholar 2400 BPS Modem 2022 OCT 25 in dec
- Sontec FORTH Computer 2022 SEP 28 in vintage-misc
- SPARCstation 2 and IPX RAM Upgrade 2022 SEP 26 in sun
- Sun 3/50 System with Upgrades 2022 SEP 19 in sun
- KIM-1 Boards of the Past 2022 SEP 18 in vintage-misc
- Ohio Scientific 400 Superboard Build 2022 SEP 16 in osi
- Miller Technology M80 Single Board Computer 2022 SEP 15 in vintage-misc
- Identicon 8080 Processor Board 2022 SEP 14 in vintage-misc
- Hand Built Z80 System 2022 SEP 01 in vintage-misc
- Kaypro II Repair 2022 JUN 29 in vintage-misc
- IMSAI SIO2 Modifications for MITS Disk System Compatibility 2022 JUN 25 in s100
- Omega Micro Systems OMS-02 6507 Single Board Computer 2022 JUN 22 in vintage-misc
- S-100 Computer Products 32K Static RAM 2022 MAR 31 in s100
- Cleaning up a HP 59309A Digital Clock 2020 NOV 18 in test_equipment
- Repairing an OSI 470 Floppy Controller and Building a Second Challenger III 2019 JUL 30 in osi
- Quick and Timely SBC 2/4 Repair and Modifications 2019 JUN 29 in s100
- Alspa ACI-2 CP/M System 2019 JUN 14 in vintage-misc
- Repairing the PDP-11/10 Power Supply 2019 JUN 05 in dec
- GW-SDK80-RAM1, a RAM Expansion Board for the SDK-80 2019 APR 01 in sdk80
- North Star Horizon Restoration 2019 MAR 04 in s100
- Debugging and Cleanup of an Intel SDK-80 2019 MAR 03 in sdk80
- IMSAI SIO-2 Compatibility with the Processor Tech 3P+S 2018 AUG 30 in s100
- Repairing The TDL SMB 2018 JUL 31 in s100
- Fixing the HP 700/43 Terminal 2018 JUL 31 in vintage-misc
- Repairing the RX211 RX02 Unibus Controller 2018 JUL 09 in dec
- Reproducing the Solid Sate Music IO-2 2018 JUL 02 in s100
- SIIG MiniSys S286 Small Form Factor PC 2018 JUL 01 in vintage-misc
- Fairchild F8 Evaluation Kit 2018 JUL 01 in vintage-misc
- 8085 Single Board Computer Revision 3 2018 JUN 30 in i8085
- GW-1244-1, a Maintainable Replacement for the Dallas DS1244 32K NVRAM/RTC 2018 MAR 17 in vintage-misc
- XT-IDE rev 4 2017 NOV 23 in xtide
- Graphing 95th Percentile in Munin 2017 OCT 19 in programming
- GW-48T02-1, a Module for Rebuilding the 48T02 RTC/NVRAM 2017 AUG 01 in sun
- Rebuilding the Dallas DS1387 RTC/NVRAM Module 2017 JUL 27 in vintage-misc
- Jekyll Plugins, Custom Liquid Tags and Blocks 2017 JUL 25 in programming
- Repairing Sun SPARCstation IPC Power Supplies 2017 JUL 24 in sun
- Building a Mail Server with OpenBSD, OpenSMTPd, and Dovecot 2017 MAY 12 in programming
- A Universal RAM Board for OSI, GW-OSI-RAM1 2017 MAY 03 in osi
- Installing DEC Handles 2017 APR 25 in dec
- A Multi-IO Board for the 8085 SBC 2017 APR 24 in i8085
- The OSI 560Z Processor Lab 2017 FEB 26 in osi
- Slot 8 Support on XT-IDE rev 2 2017 FEB 05 in xtide
- IBM XT Slot 8 Support for XT-IDE 2017 FEB 03 in xtide
- Removing Cookies and Sessions from Rails 5 2017 JAN 16 in programming
- Cisco Aironet Access Points 2016 OCT 06 in network
- Building a Lego TC Logo 9767 Interface 2016 SEP 12 in vintage-misc
- XT-IDE rev 3 2016 JUL 06 in xtide
- TEI MCS-CPU 8080 CPU Board 2016 MAY 31 in s100
- Expanding to a 64K RAM Board 2016 MAY 17 in osi
- Building a 32K RAM Board 2016 APR 23 in osi
- Cloning the OSI 495 Prototype Board 2016 APR 22 in osi
- Cleaning up the Challenger III 2016 APR 20 in osi
- Ferroelectric RAM Part 1 Prototyping 2016 MAR 29 in s100
- Quick EPROM Timer Script 2016 MAR 21 in programming
- Upgrading BDV11 ROMs 2016 MAR 19 in dec
- IBM FSU RAM Board for the S-100 Bus 2016 JAN 20 in s100
- A DC Power Supply for Rack Gear 2016 JAN 03 in hardware
- Configuring MariaDB Replication 2015 DEC 23 in programming
- OpenBSD, Hurricane Electric, and Dynamic IPs 2015 NOV 04 in programming
- Reporting Dropwizard Uptime via Metrics 2015 JAN 23 in programming
- Configuring an access log for Dropwizard projects 2015 JAN 22 in programming
- Multipart HTTP POSTs with Groovy's HTTPBuilder 2014 SEP 24 in programming
- Cromemco CDOS Tools 2014 FEB 07 in vintage-misc
- Cromemco 4FDC Floppy Controller 2014 JAN 30 in s100
- Pragmatic Designs DBM-1 EPROM Simulator 2013 NOV 16 in s100
- Power On Jump Board for the S-100 Bus 2013 APR 17 in s100
- Isolated 24V Relay Controller 2013 FEB 28 in general
- External 5.25" Disk Box 2013 JAN 11 in vintage-misc
- Intel SDK-85 Checkout and Cleanup 2013 JAN 02 in i8085
- Quad Port Gigabit PCI Ethernet Card Roundup 2012 AUG 03 in general
- Sabernetics I2C OLED Display Testing and Demo 2012 JUN 28 in general
- New Static Site Layout with Jekyll 2012 APR 20 in news
- A 1702A ROM and 2101 RAM Board Using the IO-2 2012 JAN 30 in s100
- The Dajen SCI -- A System Central Interface for the S-100 Bus 2011 NOV 03 in s100
- 8085 Single Board Computer Revision 2 2011 OCT 29 in i8085
- A Debug Board for the S-100 Bus 2011 SEP 01 in s100
- Modifying the XTIDE and Industrial Flash Modules 2010 DEC 16 in xtide
- 48 Hours of Apple IIe Hacking 2010 NOV 09 in vintage-misc
- Walnut Creek CP/M Archive CD-ROM via BitTorrent 2010 OCT 25 in vintage-misc
- Scrolling LED Displsy 2010 SEP 19 in i8085
- Building an 8085 Single Board Computer 2010 SEP 02 in i8085
Someone did a very poor job of packing this HP 6235A adjustable bench supply, which didn't help the water damage inside it. I wanted to use it in place of our larger Lambda LPT-7202-FM supplies for a project, so it needed rebuilt.
This 32K S-100 RAM board was purchased with a larger lot of other S-100 equipment. It's manufactured by Yang Electronic Systems, INC. Very little information seems to exist. We'll take a look at it, clean up some battery damage, and get it working!
I bought this OSI 600 Superboard II from Herb Johnson in nonworking condition at VCF East a few years ago. Time to get it going!
Part two of the OSI CD-23 hard disk system repair with Shugart SA-4008 14 inch Winchester disk at the System Source January 2024 workshop.
This HP 10544A high stability 10 MHz oscillator module was found to be defective during the upgrade of a HP 5326B Timer/Counter/DVM. We'll open it up and have a look!
Repair, diagnostics, and timebase upgrade on a HP 5326B 50 MHz timer/counter with DVM option and Nixie tube readout. This older counter is still a fairly useful instrument!
Bring-up, testing, and repair of an OSI CD-23 hard disk system with Shugart SA-4008 14 inch Winchester disk at the System Source July 2023 workshop.
The System Interface provides some important functions to the 8085 SBC rev 1, as well as a prototyping area.
I wanted to use the Intel 8085 in an upcoming project, and decided to clean up the original 8085 SBC rev 1 and put it to use!
The MTU Visable Memory is a bitmapped video board for KIM-1 and compatible computers. It uses an 8K x 8 bank of DRAM in a dual-ported configuration, displaying the actual bit-for-bit contents of memory on the screen, rather than converting to characters or using graphics elements. This one was repaired for a customer.
I bought two of these Certek SBC85-2 boards from an equipment reseller we use. They're basically Intel's three-chip computer implementation from the MCS-85 manual, but use a 2716 type EPROM instead of an 8755A.
The General Radio (Gen-Rad) 1192B is a compact 32 MHz counter with Nixie tube readout. It's a basic unit, with features roughly equivalent to other midrange counters of the era. This one required a bit of cleanup and repair.
Like many machines of the era, the Pegasus II is a turnkey S-100 system that runs CP/M. This one came with a pile of diskettes and documentation, but some weird problems.
In March 2013, I'd finally gotten enough hardware together to try and run DEC RL01 pack drives with my PDP-11. Sark and I got together to clean a bunch of packs and get our respective systems set up and running.
I ended up with four of these little Gralex panel meters from some scrapped BAFCO frequency response analyzers. They're typical 1500 mV panel meters, but use Panaplex planar neon gas discharge displays.
The Krohn-Hite 5100B is a high quality function generator from the 1970s. It has a variety of features which make it a useful tool. This one required a little cleanup before being put into service.
A little homebrew or shop built counter with Nixie tube readout. This counter has been in the glow discharge project bin for a while, let's take a look at it.
The HP 59304A is a 12-digit numeric display that connects to the HP-IB/GPIB bus. It displays up to 12 numerical digits (and a few other characters) on a Panaplex neon gas display.
Rebuilding and using an empty Sun 511 SCSI shoebox enclosure. This shoebox came up on a mailing list with no drives, and ended up being quite a bit of work!
After searching for quite some time, I finally acquired a Sun 19 inch ECL monitor! This monitor arrived working, but did require cleanup and repair before serious use.
Ampro produced a well-known series of single board computers called Little Boards. The first was the Little Board Z80 and is of course Zilog Z80 based. They also made a chassis for this SBC, the Series 100. This one gets a full cleanup and repair.
This rev 0 Altair 8800 is the first I've worked on that was completely unexpanded! Only two S-100 card sockets were installed, and the system came with its original 8080 CPU board and 1K static RAM board.
The Shiva LanRover/E PLUS is a fairly standard remote access/dialin/dialout/terminal server from the 90s. It requires firmware loads from the network but fortunately those files have been preserved! Let's take a look at some minor cleanup and repairs, and what it takes to bring up the LanRover/E PLUS.
This server was the first "proper" server I owned. It was bought cheaply online, a leftover from the dot-com bubble. It sat unused for many years in my parents' basement, now it gets cleaned up and put back to work.
DEC produced a series of modems intended for end users. This one is the Scholar DF 224-AA, a 2400 BPS non-Hayes modem with some interesting hardware inside.
ITI Audio/Sontec is known for analog audio mastering equipment. During the 1980s, they designed and prototyped a series of FORTH computers intended to control a mastering product which was eventually cancelled. This writeup takes a look at some of the extant prototypes.
SPARCstation 2 and IPX systems are closely related, and max out at 64 MB RAM on the motherboard. There exists a somewhat rare RAM upgrade, in SBus card form-factor, which allows these two machines to be expanded to 128 MB!
The Sun 3/50 was Sun's lowest-end Sun-3 offering. These limited systems were intended to be (relatively) cheap diskless workstations in environments like computer labs.
In Summer 2008, I was working for a surplus components dealer while on break from college. I came across a number of KIM-1 systems, all which have been sold by this point. Here's a look at those systems.
This is actually the second original blank Ohio Scientific 400 Superboard I've had, but the first I've built. After scanning for reproduction, this 400 board was built up for testing some interesting processors a friend had. Parts choices were made to give a vintage look to this modern build.
Cleanup, repair, and testing of a Miller Technology M80 single board computer. This little SBC is Z80 based, includes ROM, RAM, and parallel I/O, and could be supplied with a ROM monitor which bit-banged serial using some of the GPIO.
Identicon produced a wide range of barcode scanning equipment starting in the 1960s. Their products eventually included microprocessor control, one of them must have used this Intel 8080 based processor board. Sometime in 2012, a friend acquired several of these boards in a scrap lot, and we hacked on them.
This hand built Z80 computer was purchased from a friend at VCF East 2018. He'd found it at an estate sale in Albany, NY. It is an interesting and very well-built system.
I've had this Kaypro II since 2010. It was a local pick-up deal and came with documentation, software, a Kaypro-branded Diablo printer, and even the black faux leather carrying cover! The machine had been stored very poorly, and is only now fully functional.
The IMSAI SIO2 conflicts with MITS' disk controller when both are at default addressing. It's possible to change the address on the SIO2, but this breaks compatibility with IMSAI software. Turns out it's not difficult to modify the SIO2 to make it compatible, with little to no reduction in functionality.
Bill O'Neill traded me one of his OMS-02 6507 based single-board computer in 2011 for one of my 8085 SBC rev 2 bare boards. We'll take a look at it, clean up the original build a little, and do some 6502 development with it.
Fixing up a S-100 Computer Products 32K Static RAM board. This board uses 2114 type 1K x 4 SRAMs and after repair was running *very* hot. 5V supply was modified, and addressing was changed to system-specific needs.
HP produced a HP-IB connected digital clock, the 59309A, which was intended to serve as a clock/calendar for HP-IB (GPIB, IEEE-488) equipped computers or assemblies of test equipment. This one needed some cleanup and repair before being put into service.
This project started out as a repair job to get an OSI 470 floppy controller working, and resulted in putting together a second Challenger III system from parts! This particular floppy controller had some very weird problems.
When a request from a fellow vintage computer hacker came through for a Z80 based S-100 system capable of running banked CP/M Plus, I chose a Quick and Timely SBC 2/4 as the CPU board, as I had two on hand. In repairing it, I came up with a convenient way to add extended memory management.
The Alspa ACI-2 is a somewhat uncommon integrated CP/M system. At first glance, it appears to be just an external drive box for 8" floppy drives; however, the enclosure contains a full Z80 system with 64K of RAM and three serial ports! It's pretty quick, and the disk controller handles double-density, for around 600K per disk.
As mentioned in the RX211 repair writeup, my PDP-11/10's power supply failed with the release of smoke during operation. I finally got a chance to tear it down, isolate the problem, and fix it.
With my SDK-80 cleaned up, I wanted a way to add more RAM and test out some ideas without permanently modifying the board. Enter GW-SDK80-RAM1, a small mezzanine board that carries 64K of RAM, ROM remap circuitry, and substitutes for the 8212 address bus buffers.
This North Star Horizon arrived with a larger lot of equipment. It had clearly been a mouse house at some point in its life, but the bulk of the mouse mess had been removed, hiding the full extent of the damage. Repair involved replacing many sockets and even some S-100 slots.
The Intel MCS-80 System Design Kit (SDK-80) was Intel's official rapid prototyping single-board computer for the MCS-80 family, which centers around the Intel 8080 microprocessor. This SDK-80 arrived with extensive modification in the user prototype area, and was not working. To restore function, all circuitry in the prototype area had to be removed. Plenty of cleanup work was involved, read on for an overview of the original condition and progress through cleanup.
The Processor Technology 3P+S is an early S-100 universal I/O board, providing both parallel and serial I/O. It is a versatile board, allowing the builder to select from many onboard options via jumpers. As shipped, it can be configured to be compatible with many other manufacturers' serial interfaces; however, making it compatible with the IMSAI SIO-2 requires some modification.
The SMB (System Monitor Board) is one of Technical Design Labs' best known products. I received two of these boards almost completely stripped of parts, and worked through them to get them back to operational condition. Along the way, upgrades, fixes, and reproduction of original parts were done which will hopefully help other hobbyists get their SMB boards operational.
A recent equipment pick-up had included a HP 700/43 serial terminal with keyboard. The terminal appeared to work, but the power button wouldn't stay latched in the on position, a common problem especially with vintage CRT monitors and terminals. The terminal was disassembled to replace the switch, which actually ended up being repaired instead. While open, the RIFA line filter "smoke caps" were also replaced, and everything cleaned.
With a friend's PDP-11/34a on the workbench, I decided to take the time to repair and test my RX211 controller, which is a DMA capable controller for the RX02 8 inch floppy system. I'd picked one up in rough shape but hadn't gotten around to repairing it.
The Solid State Music IO-2 is one of my favorite S-100 boards due to its versatility and flexibility. It is usually the board I grab when I want to quickly interface something to the S-100 bus. Vintage IO-2 boards are difficult to find and usually require rework to remove the previous owner's projects, so I decided to reproduce the IO-2 and make the boards available to others.
I'd been casually looking for a SIIG MiniSys S286 since about 1998. The S286 is a 286 AT-compatible PC about the size of a narrow shoebox. With onboard IDE, floppy, VGA, serial, and parallel, and a single 16-bit ISA slot, it's a fairly useful AT-class machine in a very small box!
The Fairchild F8 Kit was Fairchild's engineering evaluation tool for the F8 CPU set. The F8 has an interesting architecture, it's a CPU produced on LSI chips, but it requires more than one chip. This F8 Kit came in a heap of scrap and was a complete basket case when acquired. It now works once again.
A third revision of the 8085 SBC! This revision had been planned for a long time, started once, abandoned, and finally restarted as a workshop class for VCF East XIII (May 2018). This SBC adopts a larger format, a new expansion bus, and is truly a single-board computer -- everything required for basic operation is onboard, just add a power supply and terminal. No add-on I/O board required.
A piece of legacy networking hardware was losing its NVRAM on poweroff, and turned out to contain a Dallas DS1244 NVRAM with Phantom RTC. This module is still made, but is expensive and has its lithium power source potted in the module. Rather than buying an unmaintainable replacement, I designed a compatible replacement module.
After assembling many XT-IDE rev 3 boards, there were a few tweaks required to make the layout a little cleaner and ease assembly. Alan Hightower reported a race condition when developing his NetPi-IDE interface, which revision 4 corrects. Silkscreen is standardized and improved, and extra test points were added for Slot 8 Support installation.
Like many ISPs, my colocation ISP bills bandwidth usage as 95th percentile. The ISP sends weekly and monthly bandwidth graphs to help in planning for bandwidth costs. While this is a common thing, it's not something that Munin supports out of the box, though rrdtool does.
With a large number of vintage Sun machines in the shop, I was stuck with having to repair or replace dead batteries in the 48T02 RTC/NVRAM modules used on many early SPARC systems. Modern replacements are not 100% compatible, so the old modules have to be repaired. There are clearance issues in some Sun systems, so gluing a coin cell holder onto the old module was not an option. I decided to lay out a small PC board to completely replace the "CAPHAT" section of the 48T02.
A 486 industrial computer on the repair bench had a dead DS1387 RTC/NVRAM, which is no longer produced. The DS1387 is a potted module containing a DS1385 IC, a crystal, and a lithium cell. Over time, the lithium cell dies, and the module will no longer keep time or NVRAM contents. Fortunately, others before me had figured out the locations of the buried battery pins and provided their solutions. Here's my fix!
During a recent bit of site maintenance, I DRYed up the Jekyll project for glitchwrks.com by creating custom Liquid tags and blocks for the site. These reduce code duplication, simplify and centralize configuration, and make the Markdown for writeups nicer.
A recent equipment pick-up included many Sun "lunchbox" form factor computers, including two SPARCstation IPCs. Both of the IPCs had dead power supplies, a result of failed capacitors. After recapping, they functioned perfectly. We'll cover which capacitors are valid replacements, clean-up, et c.
I recently replaced a paid email service for a this small site with OpenBSD, OpenSMTPd, and Dovecot. OpenSMTPd is OpenBSD's internal SMTP server project, though as with OpenSSH it is also released in a portable form for other UNIX-like operating systems. Documentation is good, and configuration was pretty easy.
A common issue when restoring, repairing, or building up an Ohio Scientific system is a lack of dense, reliable RAM. OSI boards do exist that provide 64K of static RAM on a single low-power board, but these are rare. There are even fewer options if you want 12-bit support for the 560Z Processor Lab in PDP-8 mode. With two prototype RAM boards built, I decided to lay out a universal OSI RAM board to meet the needs of as many OSI systems as possible.
Many DEC cards and modules use plastic extractor handles. These handles can become damaged, and some cards (new made prototype boards, for example) often come with no handles. DEC attached them with tubular hollow rivets, while most hobbyists are stuck with pop rivets or bolts. Here's how to properly rivet handles on!
Since the 8085 SBC was designed to be expanded, the first step was in building an I/O board. This board includes an Intel 8255 PIA for parallel I/O and Zilog 8530 SCC for dual serial channels. With the Glitch Works Monitor, it provides a basic, usable 8085 system.
The Ohio Scientific 560Z "Processor Lab" is an unusual coprocessor board for the OSI bus -- it allows interfacing a Z80 and IM-6100 PDP-8 on a chip and controlling them with the 6502 through a driver package. This package not only allows you to load and examine memory for the coprocessor(s), but also controls timing, single-stepping, slow stepping, and I/O emulation. It's a very rare board, with only one known functional board in existence, until now!
Part of the purpose in provinding Slot 8 Support as an optional daughterboard was to allow it to be added to other revisions of the XT-IDE. Installation on XT-IDE rev 2 is almost as simple as with later rev 3 boards, and works with all of the rev 2 features -- ROM, IDE, and serial port.
The IBM 5160 PC/XT has eight ISA expansion slots, but slot 8 has slightly different electrical requirements. As a result, many boards do not work in slot 8, and those that do usually require a jumper to enable/disable slot 8 support. While the XT-IDE rev 3 was designed with slot 8 support omitted, I decided to design a daughterboard to provide it. In the course of designing it, I was also able to apply it to the earlier XT-IDE designs!
In transitioning from Sinatra to Rails for site services, I ended up removing pieces of Rails 5 that were not relevant to my project. This post covers removing cookies and sessions and their related configuration options, and what can and cannot be removed.
I picked up some used Cisco 802.11 access points a few months ago, and finally got around to hacking on them. They're available for cheap as used equipment, especially if they're loaded with LWAPP firmware. This is my experience with getting them up and going in autonomous mode.
The VCF Museum at InfoAge Science Center recently acquired a Lego TC Logo kit. While it included the IBM PC compatible ISA interface, the Lego 9767 interface card was missing. Fortunately, it is a simple card and is already well-documented on the Internet. A good excuse to lay out an Apple II protoboard though!
When a request for assembled XT-IDE boards came up on the VC Forums, I took the opportunity to make some changes and improvements to the XT-IDE rev 2 design. Mostly a board respin, this project's goals were to make the XT-IDE easier for hand assembly, more self-documenting, and easier to configure.
I picked up a TEI MCS-CPU 8080 board at the Vintage Computer Festival East XI. The board came with no documentation, and no documentation was available online. It mostly worked, but had a few functions that weren't behaving correctly.
The 32K RAM board project was built with expansion in mind. Here we expand it to 64K with another 32K x 8 static RAM using the same 4K segment selection as the 32K board. Provisions for memory management allow for expansion beyond 64K using Ohio Scientific's memory management strategy.
With a quantity of 495 prototype boards in hand, it was time to build up a RAM board for the Challenger III. My implementation uses a single 32K x 8 static RAM in DIP packaging, which is split up into eight 4K segments, each of which can be enabled or disabled individually. It's also expandable to 64K and beyond due to a few design decisions.
The Ohio Scientific bus is pretty easy to interface with, except prototype boards are hard to find! Chunks of perfboard large enough are expensive, the insertion/extraction force of the Molex KK-156 connectors required soldered connections, and Ohio Scientific's 495 protoboard is unobtainium. When I finally found an OSI 495 board, I decided to clone it.
I've had a Challenger III for a few years and apparently never documented it! I pulled it out this week to work on an OSI related project only to find it was in bad need of a cleaning. I fixed a few problems along the way. It's now back up and running with a 510 triple CPU board and 48K of RAM.
This board has taken so long to get together, my sample ICs are from before Cypress bought Ramtron! Ferroelectric RAM is basically core on silicon, using tiny magnetic domains deposited on silicon -- it's even destructive read. I've used it in several projects, and have been working on interfacing it to the S-100 bus.
I was erasing a pile of UV EPROMs today and got tired of interrupting what I was doing to go unplug the EPROM eraser when 20 minutes had elapsed, so I made up a little cable to control one of my relay-switched outlets using the serial handshake lines on a serial port. A few lines of Ruby later and, problem solved!
My MINC-23 came with a BDV11 loaded with the standard turnkey boot ROMs, which requires manually entering bootloaders for things like TU58 and MSCP boot. The BDV11 can be upgraded to more complete boot ROMs using images from a PDP-11/23+.
Wait...an IBM made S-100 RAM card, using IBM FSU static RAM modules?! Apparently, yes. Here's a look at the card and the story about why this even exists.
I've got a few DC powered devices in the server rack, and wanted a way to get rid of multiple plug packs, wall warts, and/or power bricks. This is Part 1 in a larger project to provide remote power cycling and load monitoring of the stuff sitting in the rack. A surplus linear supply is gutted and refitted with modular switchmode supplies.
MariaDB/MySQL replication provides an easy way to do realtime database backup, or allow for high-speed LAN access to a read-only reporting DB. Here's my method for getting a new replication slave running from an existing live DB.
Hurricane Electric allows dynamic updates for your end of the IPv6 tunnel, but OpenBSD needs to be made aware of the changes too. Here's a simple script to accomplish that.
Another simple configuration task with insufficient documentation! Get your actual application uptime from Dropwizard's metrics.
One would think that access logging would be a common task for any application, but getting here took half a day of digging through incorrect documentation.
Groovy's HTTPBuilder, an extension of Apache Commons HttpClient, allows multipart HTML POSTs, but documentation and useful/recent examples are lacking. Here's an example using non-deprecated methods to send multiple files and a few string params to a RESTful service and handle a returned binary.
With a Cromemco 4FDC and no boot media, getting a functional system was not entirely straightforward. Tools exist for bare-metal bootstrapping CDOS with a 16FDC, but they're incompatible with the 4FDC. Fortunately, there was enough existing work and experience in the area to hack together a solution!
This one goes back to my first bit of S-100 hacking -- getting a Cromemco 4FDC up and running. Five years later, my 4FDC finally formats a floppy! Here we will discuss some of the tips, tricks, resources and myths about the lowly 4FDC.
I picked this board up from a popular online auction site with no documentation or cables. It's an EPROM simulator -- it can replace two 1K EPROMs or a single 2K EPROM with RAM for rapid development without the need to program/erase EPROMs. A handy board, but no one has information on it!
One of my S-100 systems uses a CPU board that doesn't have a power-on jump function. The ROM board doesn't have it either. It's a turnkey system with no front panel, so I had to come up with a way to get the CPU to jump into the ROM board's address space without starting the ROMs at 0x0000.
Anyone else have a pile of relays in the parts bin with 24V coils? I do, so I've designed an isolated controller board that includes the power supply, current loop drive circuit, and a DIP16 footprint relay. Now I can make use of my large stock of relays without building a point-to-point power supply and controller every time.
This disk box was purchased to serve as a universal disk box for various projects. It came without drives and required a bit of creativity to safely mount both linear power supply boards.
The Intel SDK-85 is the official Intel 8085 development system for the evaluation of MCS-85 family parts. I finally found one in reasonable shape for a decent price, cleaned it up, and brought it back into service.
I was recently tasked with building a new pfSense box for the office. We needed three or four Ethernet ports, and wanted to use a 1U Intel Atom based server. Finding a quad port card was a little challenging, so here's a writeup on picking the right card for your build.
The Kickstarter-funded Sabernetics Technology OLED Display arrived yesterday. Before committing it to a project, I wanted to ensure the display was functional and get a feel for its daylight readability. The Bus Pirate was the obvious choice for prototyping.
I finally finished rewriting the site using Jekyll, a blog-aware static site generator written in Ruby. Although the process required reformatting all existing site content, the move appears to have been well worth it! Expect a higher frequency of updates now that writing an article only involves creating a textfile and executing a script.
Building up a Solid State Music IO-2 board as a 1702A PROM reader and 2101 static RAM board using period components. Useful for reading 1702As and testing 2101 SRAMs for use in other projects.
The Dajen SCI is a relatively unknown S-100 board with a ton of highly useful features! Documentation and information on repairing, using and modifying the SCI.
The 8085 SBC has been revised, now including 64K of memory devices on-board, a cleaner layout, thicker traces, a few more expansion bus signals, and corner mounting holes!
Details on my S-100 debug board. This board is the result of much testing (and fixing) with my original debug board, which was far less thought out. An essential device for low-level debugging without a front panel, especially if you've got a CPU card that may or may not be working!
This page is a composite resource for using industrial Flash modules as hard disk replacements in vintage PCs, as well as a modification I performed to the XTIDE controller board.
I finally got time to play with an Apple IIe I'd picked up cheaply. Getting CP/M running with a Microsoft SoftCard clone was easy...but getting new files to CP/M wasn't!
A friend of mine sent me a full image of the last Walnut Creek CP/M archive distribution on CD-ROM. I've created a BitTorrent tracker for it and uploaded it on 25 October 2010 -- 16 years from its release.
Interfacing a PDSP-1881 LED character display with the 8085 SBC. I wrote software to scroll a message across the display for the 2010 Maker Faire in NYC, utilizing a circular array and FIFO.
Designing and building an 8085-bases single board computer, then turning it into a proper etched PCB! This page documents its construction and testing.