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Digital 54-22703-01 Motherboard – L2 Cache

After making this motherboard fit into the IBM PS55/z, I realised I hadn't decked it out fully. I'd mentioned cache in the first post, and finally got around to ordering some. The goal was to speed up the poor old 486 as it wasn't running as fast as I would've expected it to. Of course, this was also all very subjected as it'd be pretty impossible to actually remember how fast my first PC actually ran!

Usually, parts like this can be pilfered from other items laying on the shelves in my apartment, but this motherboard needed specific 'TAG' RAM, as well as the standard 32KBx8 static RAM chips. I had to go hunting...

Required components

Back to Pafe 45 of the User Manual for this motherboard and we find that we need eight 32 KB x 8 cache SRAM chips and three 16 KB x 4 cache tag SRAM chips to max it out. Straight to eBay and I found a seller in Israel with the correct parts. I incorrectly ordered two sets of TAG RAM chips and only half the required static RAM chips... whoops... fortunately I could pilfer those off another board!


The TAG RAM chips are labelled MCM6290BP25 RIQAB9131.


As per usual... always be careful when inserting ICs. Make sure their legs are aligned with the sockets and don't press until it's safe... otherwise this happens!



With everything in, we just need to adjust the jumpers...


Set all four jumpers (J3,J4,J6,J7) to 2-3... and then boot!



Test Software

Go here and download anything that starts with Cache. I then tested them all out...

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They all showed that any data size under 256kb proved quick response times. The rest started spiking as more operations were required. The CCT386 application had awesome graphs.


Now to work out if the games actually operate faster...

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Microchannel Sounds Cards (aka Hen’s Teeth)

I was interested in these when the IBM PS/55z was on its way as I wanted to deck the machine out with sound. Turns out that MCA is a rare breed and actually-interesting cards are impossible to come by.

Imagine my surprise when I saw an MCA ChipChat Sound Card (with wavetable addon!) appear on eBay. It started at AUD$50 and I was interested... just because it had to be an investment to sell later?

Here's the description...

This a ChipChat Sound-32 Card for a IBM PS/2 Microchannel computer.
It comes with original box and contents. Including reference disk and driver disk.
Drivers are for DOS, Win (3.1, 95, NT), OS/2 (2.x, Warp)

And a few pictures:


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So yeah, nothing special... not even a mention if it works? Anyway... the 7 days were nearly over and it had gotten up to AUD$141. I was a little disjointed, but yeah... it's a relic! I mean, it's beautiful.. but... I wasn't expecting the outcome:


I'm very happy that someone, who I hope REALLY REALLY wanted it, got a very nice piece of computing history!

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Testing EGA/CGA Cards

I'd picked these up a while back but never thought I'd get to test them. I don't have any monitors that support the old standard and haven't actually seen any available on eBay for a long time. I was quite surprised when I realised that the GBS-8200 that I picked up for my MSX would work to convert the frequencies! I'd only ever expected to use it for the MSX RGB signal.


This card (thanks,!) has the ability to output both EGA/CGA and VGA! It's 8-Bit ISA and it a little worse-for-wear...


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This seems to be quite an advanced card of its era. Happily outputting to the monitor you happen to have and allowing for future upgrades! It also even seems to have the VGA auxiliary header?


This card (thanks again to!) is a little older. It has a header for a light-pen and suppsoedly two composite video inputs!?


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I had purchased the bare-bones board and never tried it. Thanks to my new desktop power supply, getting it going was really very easy. The board comes with a standard DC jack, but also a pin header for the input voltage. Instead of using a crappy wall-wart, I instead powered it on the supply, having the additional benefit of knowing the current requirement!


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Ian Stedman thoroughly reviewed this board. His outcome was that there were a few issues, but a strong power supply is not needed. It turns out that my testing below shows that it hardly needs 5v at 400mA!

You can see where I've soldered on to for the EGA/CGA input. It's the bottom-right 5-pin header and I couldn't find an acceptable plug. In the end, a quick bit of tinning worked. There's 4 wires: R,G,B, Sync and Ground. The EGA Pinout on Wikipedia (CGA is nearly identical) shows that there are two sync lines, but we only have one on the GBS-8200! As mentioned above, we'll use the bottom-left connector on the board.

Combining HSync and VSync

We'll need to combine the Horizontal and Vertical Sync outputs from the EGA signal as the GBS-8200 requires a single Composite Sync signal. To do this, we can use an XOR or OR gate. Ian is our saviour once again and has provided a circuit to combine the signals.

Build the circuit as he's described. I actually found that either XOR or OR worked fine with the GBS-8200!


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I probably should've tested some games...


No such love. Same connector, but a very different video signal. Turns out it's actually a digital TTL signal that this unit cannot process. If you really want yo convert it then you'll need to buy a GBS8219.


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Is that a printer port? Space saving tech! I don't have any plans to pay for a Hercules monitor or an 8219, so this is going straight on eBay.

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High-Capacity Metro Trains (HCMT)

The first HCMT has been 'constructed' at Newport and recently passed through Hawksburn late at night. It was done after-hours to permit slow-running... as I'm sure they've measured the platform clearances... but weren't game to trash their new toy!

Whilst getting ready for the main event... I happened to see a few other consists on the radar. First up we have two SSR T-Class locomotives hauling the inspection vehicle IEV102. Running slowly, you can see it has the light shining onto the overhead, making sure it's within tolerance.

Next was the midnight down steel... but I missed it... too busy playing Pikmin 1 via the Dolphin Gamecube Emulator!

But then the down Apex Gravel train showed up... and came through. This had a full load and was working pretty hard up the grade. Looked and sounded great!

Finally, the main event (at 0130 in the morning)! The consist was pretty random: S302 up front, 20 grain cars, S317 + T + T, a brake van and then the actual HCMT! The extra loading was required as the HCMT wasn't 'braked'. Or that's the only reason I can think of... they couldve just had the 2 S or T on either end, but they may not be able to pull the train to a stop as they'd not be able to brake hard enough. Instead they used the bogies of 20 grain cars to make sure the weight on the end had no impact on the running train.

What a night! And what amazing lack-of-sleep!

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DOS USB CD Drives? Of course!

After mucking around trying for a while trying to get the new Compaq motherboard into the old IBM PS55/Z, I realised I'd wasted a lot of time playing with SCSI cards. This motherboard has a USB port! Can I use an external USB CD drive in DOS? It turns out the answer is yes!

Download USBASPI.SYS from here and then a USBCD.SYS (choose your brand) from here. I fluked it and tried the first USBCD1.SYS driver which worked perfectly! Firstly, copy the files to your HDD (I always put them in C:\DOS\), and then edit CONFIG.SYS:


And don't forget AUTOEXEC.BAT as follows:


And reboot...


Out with the old and in with the new!


Meanwhile, Windows 98se kept locking up (whole machine freeze!) at Programs on the Start Menu. I actually had to unplug the CD drive and reboot to get it to continue! But the end result was lovely...


Time to really make this motherboard fit!

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IBM PS/55 Z – All About The Pentiums

Found this at the local flea market on the weekend. After spending many nights replacing the guts of my IBM PS/55Z with a 486 DX2/66, I saw the specifications of this motherboard and couldn't resist snatching it up. 166mhz! PCI! ATX! 96mb RAM! USB! What more could you ask for in a vintage machine? I wonder if I should try and make it fit!?


Turns out it's the motherboard from a Compaq Deskpro 2000. Am I happy to have the Compaq splash screen display when the machine powers up? I believe the BIOS will also be tricky to get into as these machines need a separate hidden partition with Compaq's proprietary tools?

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A quick Google lead me to realise that building an AT to ATX adapter would be a nightmare. I'd need to create a solid +3.3v DC supply from the 5v rails and also muck around with more sense wires? Might be easier to just rip out the power supply and slap an ATX unit in there. Would have to merge in the CRT electronics though... Of course, it's also ever-slightly too long, so there'd need to be quite a bit of hacking to make it fit.

Such delight at finding this beautiful piece of equipment! ... Oh wait, maybe this will be easier than expected!

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Repairing a 3rd Gen iPod Dock

I've had this little beast for a very long time and thought my amplifier was playing up when the left channel started cutting in and out. A quick amount of cable-jiggling proved otherwise: the jack on the back of the iPod Dock was frail.


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No amount of stickytape would keep the cable in contact with the socket, so I endeavoured to open the unit up. Turns out there's large tabs on the inside 'side' edges and smaller tabs along the longer edges.


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The cracked solder joints were immediately obvious and a quick touch-up with the soldering iron brought the conductivity back from a crackling zero to 'awesome'. I really love easy fixes!


Oculus Rift DevKit 2

I always managed to be surprised at things that turn up at flea markets. I was stumbling through Laverton Market on the weekend and came across this... for AUD$5.00. Is this retro? It could well be... it's nearly vintage nonetheless!


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Turns out it's the Oculus Rift Development Kit 2. More infomration here. The headset has a cable running off it with USB and HDMI. There's also a USB and audio-style port, hidden under a cover on top. It's also got a random date on the side and a differing price tag of AUD$2.00? Did I get ripped off?

Testing it

Seemed to be simple enough... Just for fun I plugged it into my laptop. It straight away showed up as a portrait screen and I could move application windows onto the new secondary desktop! The LCD looked a little sketchy, but I assumed it was nothing that couldn't be cleaned off!

With the basic shake-out complete, I downloaded the Oculus Rift software and installed it. Whilst reading the download notes, I realised it hinted at another piece of hardware: a sensor. My kit didn't come with this! It seems that the sensor (looks like a webcam) tracks the IR output of the headset to determine your physical position. Supposedly you can use the headset without it and you'll just get rotational giroscope-based movement.

Once the software was installed, I plugged the unit back in and ... well ... nothing but errors. The Oculus Software reported that I had a USB connection, but no HDMI connection. No amount of cable-tweaking-or-swapping managed to get it to work. Long-story-short, my laptop wasn't even capable of supporting the unit and would never actually be able to output HDMI in the format the headset wanted. It would actually be really nice if the software provided this tiny hint, instead of just telling me that the HDMI connection was unavailable, but it actually turns out I skipped the entire first step... there's more on that a few sections below.

Digging deeper, it turns out that the Oculus software installs a driver for the headset and prevents it from being used as a second monitor. The point that I saw a desktop when I first plugged it in, was just because the Oculus display drivers were not installed. Of course, I had no idea that this was the case and thought I'd actually killed the unit! I proceeded to tear it apart ... was it a loose cable or other broken component?

What Does It Look Like On The Inside?

I had read another review where the author had described the whole unit as a 'kitbash'. I chuckled at that, as it's a common term in model railroading where you take an off the shelf product (or multiple) and blend them together to make something new and unique. Well... that's actually what they've done here... to the point where the LCD is actually a Samsung Galaxy Note 3 screen, complete with phone face-panel and touchscreen digitizer!

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The best part? The LCD in my unit is crappy... it seems to have two areas of pixels that are totally burnt out. I went ahead and ordered one on eBay as I had assumed that this was the reason that the unit had stopped working.


Of course, it struck me later on, after re-assembling the unit and stowing it away to wait for the new screen, that it could just be my laptop!? I downloaded the Oculus Compatibility Check Tool and was quickly told that my laptop hardware was useless. Muhahaha... what a waste of time... What to do? I have a desktop with a real NVIDIA card and realised I should've used it to begin with. I downloaded the Oculus Legacy 0.8.8 Runtime and gave it a whirl... success! I used the older version as there were conflicting reports online that this older DK2 unit only worked with older software.

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With the test application, I managed to happily sit at my desk and swing my head around. The movement was actually pretty damn flawless and the image quality very impressive! I then tried to load up games like GzDoom VR and Quake II VR but none managed to initialise the device... I assumed they needed the newer version of the software.

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With my head at the right angle, I could really see how bad the LCD was also!? It seemed to be burnt at the same place on both screens!? Maybe some really bright light in a game cooked the crystals? (Excuse the dust... but look for the pink dot)


Throwing caution to the wind, I downloaded and installed the standard (latest) Oculus software on my desktop. Low-and-behold it (took forever to download and install) found both the USB and HDMI connections!

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During setup, it whinged that it couldn't find anything, but skipping that worked. In the actual app I then got a warning that the DK2 was no longer supported. Dismissing that, I was finally presented with an error saying that it couldn't find the sensor.


Urgh... back to square zero...

Trying to play games without the sensor

This just doesn't work... I got a message box saying that the sensor can't be found and was presented with an OK button. Clicking this button was impossible though! Firstly, I needed a 'touch' device that the Oculus supported so that I could actually interact with the 3D world. At this point I was worried about putting in more money to something that I could never get working. I didn't know if clicking OK will actually let me into the game!?

Meanwhile, can't I just buy a replacement sensor? Turns out it's a big, fat no! Googling is pretty funny on this topic. It seems that during production, the sensor and headset are paired via serial number. The hardware has been open-sourced (here's the actual files), but the firmware for the sensor is not available! The quote from them is: The sensor also utilizes microcontrollers which require firmware which was not redistributable. Grrrrrrr!

Before I start an attempt to hack together a sensor (here's great inspiration!)... I wonder if I can (cheaply) get that button pressed to see if the games will continue without a sensor?


To press that magic OK button, I knew I needed a working controller. I considered borrowing an XBOX 360 controller from a friend, but then found an article using an Xbox 360 Controller Emulator. It seems that others have had luck! (Original French article here)

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I tried my hardest to fake the controller, but had no success... I couldn't get the DLL in the right place to stop the main Oculus app from whinging that nothing was connected. Of course, the best thing at this point was to get an actually-supported controller. I didn't bother trying to use my Android phone can emulate one. Instead, I picked up a cabled controller from a nearby second-hand store.


Finally, Oculus recognised it. Of course... it didn't let me press that magical OK button... I was stuck without a sensor!

Reverting back to 0.8.8

I was out and about taking the MR-2 for a spin and the thought came to me: I'd had the demo working fine on 0.8.8... there were no camera/sensor warnings! Maybe I should downgrade and find compatible software? I uninstalled the latest software and re-installed 0.8.8. I then browsed over to this list of compatible software. Oh look, Duke Nukem 3D!


Hahaha... SHAKE IT BABY. It just worked perfectly... with controller and all! I then went back to the GZ3Doom Releases Page and scrolled down, looking for that magical SDK value of 0.8.8. It also worked!


Ok, nice... I have things to do with this now.

We get to wait with Totoro!?

Whaaaaaat... Someone has built a 3D scene of the bus stop!? But the links are all dead... can anyone send me one that works?! Full review of it here, but still no valid links. The review indicates that Fire Panda are the author. But there's nothing on their actual site. Ohhhh: Due to a request by Studio Ghibli, these demos will sadly no longer be available. I hope that everyone who got a chance to play them enjoyed them and I hope you enjoy future projects I am able to bring to you. Thanks again for all your support! Boo... I'm only a few years late!

Turns out there's a whole world of user-authored content at SketchFab. Here's the train from Spirited Away. That Sea Railway was always a cool idea.


This all seems promising, but there's no compiled binaries for Windows? I don't have a Linux machine to muck around with that has a good enough video card... hmmm... that's a little bit too much effort to go to. Actually, my main machine has started dropping the ethernet connection and blue-screening... maybe it's time for a rebuild!?

Build your own sensor?

There's a great set of documents at on Hacking the Oculus Rift DK2 (Part 2, Part 3, Part 4) which describes how to read the data from a real DK2 sensor. This is all well and good, if you have the sensor... in my situation, this code will come in handy once I manage to fake a sensor. Philipp Zabel's ouvrt project also looks interesting as it is able to extra ROMs from DK2 sensors. This may only be the USB configuration ROM, but it'll totally help with the faking.

Where to start? The Open-sourced project of the DK2 has a hardware schematic of the sensor which shows that it's based on an eSP570. Turns out these are pretty hard to find... but Alibaba seems to have some available.

I thought the camera lens would sense the timing flashes that the headset produces, but it seems that this is done by an IR sensor built-in. There's then a micro-controller to parse this. You can see the sensor in the tear-down here. It seems to be something similar to this dis-continuted sensor. Urgh...

But I'm getting carried away... this is all totally-probably worth a probably-totally separate blog post...


How To Actually Connect An External MIDI Device

I started this journey thinking that MIDI cables were really simple. There's a joystick-style plug at one end and two DIN-5s at the other for MIDI-OUT and MIDI-IN. MIDI output from the computer comes out the OUT cable and MIDI you're receiving from elsewhere comes into the computer on the IN cable.

So, when you're hooking up an external module, like this MT-100, you simply connect them up...


There they go, OUT to IN and IN to OUT. Right? You want the output from the PC (be that the soundtrack of a game) to go into the Synth/Module to be processed. Like so... I don't really care about the module output at this point, but for-neatness-sake, let's plug it in!


IT TURNS OUT YOU DON'T WANT TO DO THIS. You're actually creating a loop and the MIDI data will come straight back out of the module and into the PC. This will then cause all matter of DMA/IRQ interrupts and you'll probably freeze your machine. I've actually just spent the greater part of two nights having DOOM II lock up every time I set both SB16 and MIDI-OUT. I went through all matter of IRQ or DMA settings, thinking the combination of a SCSI card, Network card and Sound card were fighting. After a quick google of vogons, I realised that the machine was freezing/slowing-down/locking-up due to the rebounding MIDI data!

This article was actually going to be titled 'DOOM II Freezes when selecting SB16 and MIDI-OUT'. Either way, do this instead... connect OUT (from the PC) to IN (on the module)...


And you'll be an uncle's monkey!

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Ahhh… Floppies

There's nothing like the smell from a fresh box of floppies. That acrid plastic fragrance, reminding you how technologically advanced these little wonders are...


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I recently found this box for a dollar at a local tip shop. Over the moon, I thought I could finally build a solid set of DOS 6.22 and other disks. I even got labels! Of differing colours!


Of course... none of them worked... They'd neither be read, formatted or imaged. I assume that fresh smell of acrid plastic meant that these had all been toasted by the sun at some point.


In the bin they go... Or maybe I should make some art.

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