Replacing an FM Towns II CMOS Battery

This isn’t something I was originally planning to write about but after all the recent posts on fixing up the FM Towns I thought I may as well finish the story off. I’ve found so little information when Googling, I’ll try to spare someone else the trial and error I’ve gone through.

At any rate, shortly after finishing a long awaited playthrough of Wing Commander, I decided it was about time to sort out the dead CMOS battery on my FM Towns II UR. I had no idea where the battery was located or how to take the machine apart which is where this guide comes in. Most of these photos were more for my reference than anything else and not with this purpose in mind so bear with the quality.

Taking the back of the case off is easy enough. Just undo the 4 screws + remove the memory slot flap and the back of the case will slide straight off. This just presents you with a second inner case of steel panels, the top of which needs to be removed by undoing the many, many screws holding it in place.


That will expose the built in monitor and the various boards surrounding it. Hopefully this goes without saying but CRT screens act like giant capacitors and are more than capable of giving out lethal electric shocks. You either want to discharge the tube or be extremely careful not to touch it. The good news is that you don’t need to go near this part of the system much so the latter should be fine. The computer part of the unit is on a separate caddy that can be slid out of the back once unscrewed.


Before sliding this out, you will need to unplug the monitor cable at the front left, the speaker cable at the front right, a connector cable at the back right and another at the top left of the case (the grey three pin plug in the photo above). It should be obvious which cables once you start sliding the unit out.


Having got this far, you need to remove the fan at the back of the case so that you can then remove the board it is attached to. You can unscrew the fan through the metal grill. There is nothing attached to the circuit board at the bottom, it just needs unplugging, unscrewing and lifting out.


Since I had no idea where the CMOS battery was, I continued stripping parts after this. A lot of these clip into place on the plastic frame so you simply have to pry the plastic clips open to release. It’s quite a neat design but doesn’t exactly give easy access to the motherboard since it’s at the bottom.


I was expecting the CMOS battery to be attached to the motherboard and that I would need to strip everything right down to that level. As it happens, I could have stopped earlier. Just below where the fan was is a little space with a black plastic tab over the top. The CMOS battery is hiding just underneath the tab. It’s attached to the motherboard via a plug and short wires so you can easily remove it.


The metal plates at the ends of the wires are firmly attached to the old battery. I pried these off as far as they would go, snipped off the remainder and soldered what was left to a new battery. Soldering to batteries isn’t exactly the best of ideas but it does the job. It’s a CR2450 battery you need if you want an exact replacement. I wrapped this up in tape and started the rebuild.

Once I had the machine back in one piece, I endured a lot more messing around before I was sure my fix had worked. I’ve been using Towns OS to set up my hard drive each time I started the PC. I still found the settings weren’t being saved if I powered off. The clock on the other hand was now keeping time so I knew my battery was working. I had the idea that maybe there was a second battery in the unit for a while but it turns out that all I needed was to use a DOS boot disk, with the setup2 program (as described in a previous post) to set up the hard disk. This then saved the CMOS settings correctly.

Installing Towns OS is nice and easy. There is a utils folder on the towns CD with an install program (it’s the icon with HD and an arrow). I did find out that this wiped my hard disk after I’d done it. Not a big deal but I won’t be importing my Wing Commander pilot into Secret Missions as a result. I had been planning on doing a video showing the last mission but I’ll do the last mission of Secret Missions II instead (when I make it that far).

Building A Composite CGA PC

Back in October, I did a post with my first attempts at getting some CGA games running on an Apple composite monitor that I’d just picked up. I sort of got this to work on a Tandy 1000 with composite colours being produced. Just not the right colours since the Tandy’s aren’t really compatible. I’d been expecting this and the intention was to use an original CGA card instead, except at this point I noticed that my CGA card was far too large to fit into the Tandy’s case. I therefore needed a suitable PC to try it out with. The next post where I got this working properly was supposed to follow shortly after but as ever with these old machines, it wasn’t that simple.


This is the CGA card I’m intending to use. It’s a full length giant of a card with an 8 bit ISA interface. ISA was the original PC expansion port interface before PCI Express, AGP, PCI, Vesa and all the others. PC’s still came with ISA slots into the Pentium era but my options with this card are more limited. With the advent of 286’s the 8 bit ISA interface was expanded with a second slot to make the bus 16 bits. As a rule, this was entirely backwards compatible except my CGA card predates the 16 bit slot and doesn’t leave a gap for the extra connector on the motherboard. In short, I need an 8 bit slot if this thing is ever going to work which limited my options.


So with that in mind, I bought myself the above Vanilla 286 PC. OId PC’s have started to get a bit expensive and I no doubt paid more than I should but a machine that has been refurbed, tested and comes with a guarantee is worth a bit with a PC of this age. At any rate, it all worked perfectly in every respect except the minor factor that as soon as I tried to use composite out, I could only get monochrome.


Having tried everything I could think of, I wasn’t sure whether it was the PC or the graphics card since I’d never used the CGA card before this. It occurred to me that given how long it was, there was enough flex in the CGA card that I could fit it into my Tandy if I bent it around the side of the case and I insulated it against the edge of the metal case with an antistatic bag. I really don’t recommend trying this at home but it did give me a means of testing it.


Sure enough, it worked perfectly as shown in Ultima 2 above. Ultima 2 was one of the better composite games on the Tandy but comparing this to the screenshots from the last post, there is still a big difference. The blue Ultima text and green dragon more or less merged into one colour using the Tandy but are clearly defined here. In theory, I could have left it at this and just used my Tandy but there is no way I’m going to torture my one and only CGA card like that. It makes me wince just looking at the photo above.

From my limited understanding, the CGA card can be told to run in either monochrome or colour by a bit that is stored somewhere in memory. None of the BIOS settings helped me out here though and I came to the conclusion that this PC may simply be hardcoded to only do monochrome. The other alternative is that there was an adjustable trim switch on the motherboard of a genuine IBM for CGA timings which was entirely missing from this Vanilla PC. Whatever the cause I couldn’t get it to work. These early PC clones were rarely 100% compatible so I gave in and sent it back for a refund.


I’d not looked at trying again until earlier this week when having finally got over the post flood house insurance bill, I felt like I could spare the cash to try again with another machine. The one I picked up was a Televideo Telecat-286. This cost more than the Vanilla PC but had the bonus of coming with a working hard disk.


For a supposedly tested machine, this thing was truly filthy inside to the extent that there is no way on earth I’d have tried switching it on without cleaning it out first. I’ve spared you the photos of 30 years worth of decaying clumps of dust and hair. Underneath everything still appeared solid at any rate with no bulging capacitors or the like. I’m not sure if weight is an indication of build quality but this is the single heaviest PC I’ve ever owned. I wondered what exactly was weighing that much until I opened it up and saw the man-size power supply taking up about 1/3 of the case.

This thing was full of expansion cards which I didn’t strictly need . The big one on the left is a monumentally large modem. As for the other two, the bottom one is a network card and the other must be a CGA or EGA graphics card at a guess but I’m not 100% certain.

I slotted my CGA card in to one of the freed up slots and then worked on getting the PC to start up. After being initially alarmed at the turbine like noise produced by the PSU fan, I ultimately decided it was supposed to sound like that and I’d just forgotten how noisy PC’s used to be. It got as far as attempting to boot up but with none of the drive lights flashing couldn’t find a system disk.

All these clone machines are different and since I have no manual and couldn’t find one on the web, I was stuck with trial and error. After a lot of fiddling around, I spotted that the floppy drive did work but was connected to B instead of A and since the BIOS was at default values the drive wasn’t detected. This got me to a DOS prompt but with no hard drive. I ignored this for now and tried to get the composite CGA working since that was the whole point of this exercise.


At the first attempt, I managed to get some composite colour but only in a thin band with most of the screen remaining black and white. A bit of searching later and I found that like a genuine IBM, this motherboard does have a small variable resistor for CGA timing located at one end of the motherboard. It’s the small round orange thing in the photo above. A tiny tweak on this with a screwdriver and my graphics suddenly sprung into full colour.


You may remember the day glow colours I got when trying King’s Quest 2 on the Tandy in composite. This time I actually got the correct colours which are not all that dissimilar to the 16 colour Tandy graphics on the left. The image is far less sharp in composite and this probably isn’t the best way to play these Sierra games but for the games not supporting Tandy graphics, it’s a massive improvement over the usual CGA palette.


I still hadn’t got the hard disk working which was a bit of a learning curve. This machine is using a surprisingly modern 670Mb IDE drive, which allegedly had Windows 98 on it at some point if I can believe whoever wrote on it. I seriously doubt this PC ever ran Windows 98 so I assume this has come from another machine. The drive wasn’t being detected in DOS and I had no idea how to set it up. Aside from an array of unlabeled dip switches on the motherboard (standard in this era), this PC does have something resembling a BIOS except you apparently have to run a setup program from the DOS prompt to set the values rather than holding a key on startup.

Much Googling later, I gave in trying to find that setup program but did come across something called gsetup.exe which is a universal BIOS setup program for 286/386 machines. As luck would have it, this was mostly compatible with my machine. I was only allowed to pick from 19 predefined hard disk types, the largest of which was 120Mb. I really didn’t expect this to work but the drive formatted 120Mb and I’ve been able to get this thing booting up without the floppy drive. I can live with the missing 550Mb. For the software I’ve got in mind for this machine, 120Mb will be plenty.


Something I haven’t done yet is swap out the CMOS battery meaning I have to go through the whole setup process every time I switch the machine on. I’d usually expect to see a little CR2032 battery on a motherboard but this has a sizable Lithium battery stuck on the side of the drive bay. This is the same voltage as lots of remote control car batteries so I’ve ordered one of them which I’ll replace it with when it arrives.


One last job was to install my first ever sound card which I’ve still got nearly 30 years later. I’ve sold or thrown away nearly every bit of hardware from that era but for some reason this got kept so I may as well make use of it now rather than just having the box on a shelf.

I’ve still got to set up the hard disk with a proper installation of DOS but 6 months after I started, I’m nearly there at last. I’ve been curious about composite CGA ever since I played my first PC games back in the 80’s. I fully intend to dig out a few of those of those relics next week and see what they look like with some extra colours.

Descent Reviews

As I suspected, the UK press liked Descent a whole lot more than I did with all of the reviews I found scoring around 90%. The bulb on my scanner has gone so it’s photos only I’m afraid until I get it fixed/replaced. I’ve uploaded the images unaltered so everything should be just about legible.

The first is a matter of fact review from the April 1995 PC Review:-


Next, the March 1995 PC Format describing Descent as the first game to better Doom:-

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This is the harshest of the reviews at 89% from the March 1995 PC Gamer:-


It scored 94% in the April 1995 PC Zone write-up, featuring an alleged guest appearance by David Hasselhoff:-

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And finally by request, here is a review for Descent 2 from the April 1996 PC Zone:-

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VR has been hitting the headlines again recently with the release of the PlayStation VR not so long back and it made me realise that I’ve not made use of it’s 90’s equivalent in a year or two, the VFX-1. There aren’t a whole load of supported games to pick from, so I went for one of the more obvious choices Descent.


Descent was originally released in 1995 in the wave of Doom clones that was hitting around then. Its twist on the genre was to allow full freedom of movement in all directions making for quite a unique experience to this day. It’s a game I already know fairly well having played it back at the time but I’ve never spent much time on it in VR.

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First as always, the plot. At some time in the future, a virus has taken over the robots being used to mine resources on the various planets and moons of the solar system. These robots have turned on their creators and started producing more deadly robots of their own. This threat could soon spread to Earth if nothing is done so for reasons that aren’t entirely clear, the player is drafted in by the bureaucratic PTC mining corporation to go in single handed and blow up the reactors in all of these mines destroying them entirely and shutting down the threat. This story is told with a static screen intro overlaid with text. Each mission then has a little briefing text before you start to advance the plot. I’m usually all for a storyline in my games but none of this adds anything in particular. It’s nice that the developers appear to have put a little effort but in truth the game would have better off taking Doom’s approach and ignoring it.


The basic gameplay formula is certainly pure Doom. In essence, blast your way through 30 levels, finding the 3 coloured keycards to get access to wherever you need to go. There is a boss of sorts at the end of every level in the shape of the reactor which doesn’t move but will shoot red spheres at you. The levels are huge and sprawling and the complete antithesis of your modern FPS where the player is led through the map. You should fully expect to get lost when playing Descent but there is a confusing 3D automap to help guide you back to the right path.


The control system is quite something to get your head around with a myriad of different weapons and options. It is fully redefinable but will still take some getting used to whatever you go far. The control system is more comparable to the lights of Tie Fighter than Doom really with steering the ship best done with a joystick since this is part flight sim. It’s also part FPS and as such has strafe controls but this time you get four of them since you can also go up and down. Not to mention rolling left and right if you don’t want to end up with the ceiling underneath you. Navigating a 3D map is hard enough without having to cope with being upside down.

The ship has independent energy and missile weapons with 5 of each. None of the weapons are especially memorable if you ask me but it is important to save the heavy artillery for the tougher enemies. There are also mines to drop behind your ship which I can’t confess to ever using much when I’ve played in the past. The energy weapons draw energy from the ship which needs to be replenished by pickups off blown up enemies or by flying through a recharge station of which there is at least one on every level. Similarly shields are charged by picking up blue spheres dropped by enemies but you don’t get to charge these up any other way.

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Very strangely for a game like this, there is a lives system which is probably almost entirely ignored by anyone playing through the campaign. If you do wish to make use of it, you can restart a level from the beginning with just the basic ship loadout. All of the enemies will still be dead and if you fly back to where your ship exploded you can pick up all the gear you had before. It can act as a get out clause if you save somewhere you shouldn’t provided you can make it back to all your lost equipment of course.


There are a wide variety of enemies in the game starting with slow moving varieties that shoot equally slow fireballs and lasers at you. It starts getting tougher when you get enemies firing missiles, especially homing missles and the Vulcan cannon firing bots that are the equivalent of Doom 2’s chaingun guy. The enemies is this game are smarter than your typical Doom enemies being able to follow you around the map and you really need to be careful when entering new areas.


For VR, Descent uses the side by side picture approach which the VFX-1 then splits up between the two eye pieces. This loses horizontal resolution which is exactly what doesn’t suit the headset since it has far more horizontal than vertical pixels. Descent 2 would support the alternative mode with interlaced horizontal lines and looks a good deal clearer because of it. As such, I wouldn’t say my view of the world is exactly crystal clear with distant objects vanishing in a blur of giant pixels. Another quirk is that the HUD is only shown on the left window and therefore in only one eye. This does make it float above the action but causes major eye strain after a while.

It does have to be said that the 3D is very effective and does draw you into the game when you can see all the laser blasts literally getting nearer and flying past. Descent is highly playable on the VFX-1 in this respect. What doesn’t work is the automap screen which doesn’t swap the mode of the headset meaning that I have to flip up the visor and use my monitor screen to see the map. Also the head tracking doesn’t appear to work correctly only moving the view a miniscule amount.

I played as far as the end of level 7 where the first boss is encountered. This is a giant ship that keeps teleporting around a circular cavern and firing smart missiles every time it pops up. This was the final level in the demo/shareware release as I recall with a lot of the enemies and weapons held back for the later levels of the full release.

7 levels is where I stopped however. Technically Descent is really impressive but I’ve always felt it lacked the spark to make me want to keep coming back to it. I love space sims and I love Doom, this should have been a game I adore but it still leaves me a little cold. Every level is large and challenging but the gameplay gets repetitive long before you make it through the first half of the game. The whole experience lacks character for me.

This really isn’t being helped by the 90’s VR experience. I’ve played a few games on the VFX-1 with no real side effects but by the time I have played two levels of Descent on it, I’m feeling quite ill. The motion sickness induced by the full 3D environment is considerable and is combined with eyestrain because of the single eye HUD. You simply can’t play more than one level on an evening unless you are prepared to suffer for it, and Descent isn’t a good enough game to justify the pain. If there was ever a game to show why 90’s VR didn’t work out, this could be it. I’m really curious to know what the motion sickness would be like on an Oculus with a full 3D game like this.

I played a little without the headset to grab a few quick screenshots and have to say the overall experience was much improved even with the screen still split in two. There are some modern source ports available which would no doubt be a much better option for playing this than DOS. I’d no doubt more positive if I’d used one of them instead but as it is, I can’t exactly recommend Descent. There are clearly people who enjoyed it a lot more than I ever did though.

Speaking of which, I’ll dig out all the UK magazine reviews I can find around here and post them up within the next couple of days.

CGA Composite Graphics And My Attempts To Use Them

For reasons that I’m sure are mainly nostalgia, my favourite gaming platform/era is and probably always will be DOS. PC games have always been fun to revisit over the years partly due to being able to go back and play them with better/different hardware. There aren’t many of these technologies I’ve not been able to get my hands on at this point but one I’ve never been able to try out for real has been composite CGA graphics.

For those who don’t remember back that far, CGA was IBM’s first attempt at colour graphics dating back to the original PC in 1981. Aside from some rarely used tweaked modes, it allowed for 4 colours at once out of just 4 predefined and garish palettes leading to PC games being notoriously ugly until EGA/PC Jr came along.

This reputation was not entirely deserved however as many games used a composite mode which through the use of the TV out built into most CGA cards could be used to produce artifact colours greatly increasing the range of colours available.

I can’t pretend to entirely understand how it works but these artifact colours are produced by the interference when certain dot patterns are sent using the American NTSC TV signal. The dots would smear together to produce a block of solid colour instead. Here in the UK, this was never an option as the PAL system we use didn’t degrade in this way. While there were composite monitors around no doubt, I’ve never seen one. In the States, they are common enough which led to me importing yet another bit of old hardware, an Apple composite monitor:-

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This was in unusually good shape for one of my retro buys as I didn’t want to take a chance on importing something this size. It did of course have a load of writing all over the back of the case. Some isopropyl alcohol (only available at the chemist over here) just about removed it all but the black writing proved stubborn. The more important matter to what it looks like, is does it actually work?

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The answer so far is sort of. I’ve tried it out with my Tandy 1000 and am able to run both the CGA and composite monitors simultaneously thanks to the dual output. There is definitely extra colour produced. It just isn’t necessarily the right colour. By way of example, Kings Quest 2 above. This is rendered in high res monochrome on the RGB monitor on the right, which is converted into the admittedly colourful but clearly wrong image on the left. These composite monitors do have a tint control which can swivelled around to change the colours but I’m unable to get it to anything sensible no matter what. As far I can tell, the problem I’m having is that the Tandy composite isn’t quite the same as real CGA.

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Apart from the hires mono, the other means of rendering composite colour was to use a standard resolution CGA image with all 4 colours shown as normal and certain combinations of coloured dots would merge together to produce the extra colours. I gather the artifact colours produced this way were more flaky but it did mean you only needed one set of graphics for CGA and composite support. This explains a lot about those garish CGA graphics in early DOS games which were clearly meant to be played in composite. One such game was Ultima 2 which doesn’t look too bad at all on the Tandy in composite, although I’m sure it’s still not quite correct.

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Here’s a side by side comparison. Even on the Tandy, this shows the substantial improvement with blue water, green grass and trees and some of the player sprites look to have hair and clothing.


I had originally planned to do a side-by-side video but trying to film this composite monitor simply wasn’t going to happen by phone. Taking photos was tricky enough. I may experiment with other camera apps but I left it for now since I’ve not got this working correctly as of yet.

I can certainly see the potential improvement to some of these ancient DOS games at any rate. The composite graphics are quite blurred with unclear text but this isn’t much of a sacrifice in your average game of the time. The main problem is my Tandy is clearly not the tool for the job. As luck would have it, I did get a true CGA card thrown in with the CGA monitor I got some months back:-


It may be about as simple as PC graphics can get but this thing is an absolute colossus of an expansion card. The original plan was to slip this in the Tandy but it’s so large there is no way it’s getting into the case. Due to the connector design it won’t go in anything except an 8-bit slot either so I can forget trying it on my P2. In short, I need another old PC (which I’m sure can be arranged) and I’ll revisit this topic another day.