Keeping Old Machines Going – Adapt-ing to the times …

For retro-enthusiasts and hobbyists like myself, it can be difficult at times to keep old computers going. As the old AT form factor met its demise about a decade ago, parts for these machines can be hard to come by, but there are a few nifty solutions that can help prolong the life of these machines …

Hard Disks

Okay, so if you’re still rocking the old ST-506 with MFM interface or maybe still hanging on to SCSI-1 well, I haven’t got much to offer except – buy yourself an IDE-capable controller that’s compatible if you can. The possibilities with IDE are still fairly alive at the present moment.

Say if you have an old 386/486 with CHS addressing that can only address up to 504/528Mb and run in old PIO modes, that’s not a problem at all – you can just whack in a nearly-new drive, almost anything will do. Even a 120Gb drive might work, but you will only get access to 504Mb, which is plenty for an old retro machine and will be cheaper and more reliable than trying to run 25+ year old hard drives.

In your BIOS, you can just set the geometry up for 1023/16/63 and hopefully smile as it works just fine … of course, you are at the mercy of the plates of spinning rust …

Unless you go with a CF to IDE adapter which allows you to use a Compactflash card to run as an IDE device. Your mileage may vary as different CF cards may or may not support true IDE mode and may or may not support CHS addressing!

Cards that are bigger than 540Mb (i.e. 1Gb) can safely use 1023/16/63 as their geometry, however, it can get tricky for 8/16/32/64/128/256/512Mb cards. You can try to work out how many sectors these cards have, and then work out how many complete cylinders there are in that number of sectors given 16*63 sectors per cylinder (i.e. your geometry is x/16/63). Or in the case of industrial CF cards, there may be parameters available.

Unfortunately, some cards may detect but fail to write – so you may partition the card, but after a reboot, the partition table is missing. This indicates the card doesn’t support CHS accesses, so you will have to try out a few cards to find some that work. Older cards tend to work better in my experience … and it won’t be any slower than a hard drive (as older machines are unlikely to even support DMA, so your cheapest CF cards may give you as much performance as you’re going to get) – in fact, it may even be faster due to shorter access times!

Of course, if your BIOS is more modern, you will be able to access up to a variety of different barriers – 2.1Gb (4096 cyl BIOS bug), 4.2Gb, 8.4Gb, 32Gb (Award BIOS bug), 128/137Gb (28-bit LBA limit) just to name a few – so you might have to disable autodetection and go with manual configuration if your drives are bigger (otherwise, the BIOS may hang). For the 32Gb case, some drive in the 40-120Gb era offered a jumper where the reported geometry is just 32Gb to get around such problems, however, you will only be able to access 32Gb unless you have some special disk overlay software which patches up this bug.

For more modern machines which support LBA, there are SATA (drives) to IDE (interface) converters, mostly based on the Jmicron chipset which can be had for $10-20 a piece. In my experience, these converters work just fine in most circumstances, and could be an easy way to attach a 2Tb SATA hard disk to an old machine with only IDE ports and no free PCI slots while retaining good performance. Otherwise, adding SATA ports by installing a controller in a free PCI slot is probably the best bet, however, you may not be able to boot from it owing to BIOS limitations.

Of course, if you would like to add storage, USB is a very convenient and easy way to do so. Unfortunately older machines only had USB 1.1 ports, or none at all. Any PC with a PCI slot can make use of a USB 2.0 to PCI controller – I recommend those with NEC chipsets as they are most compatible with devices, VIA is to be avoided! Using these, and a modern operating system, it is possible to attach USB mass storage devices and or other USB devices. If you are running Windows 98 though, it is actually possible to get USB storage to work by installing these drivers. It’s a good reason to try and get Windows 98 working instead of running Windows 95 for older equipment.

Adding an IDE interface could be a very worthwhile investment because it will let you install a CD/DVD drive. Generally in AT machines, controllers only support one IDE channel – supporting two devices. Finding a soundcard with an IDE port and configurable jumper I/O Base and IRQ settings would make a perfect secondary IDE port for the CD-ROM drive, allowing you to run two hard drives, or to do disk-to-disk cloning. At least, this way, you’re not chasing SCSI drives, caddies or terminators.

Power Supplies

One of the more failure-prone devices in a computer is its power supply, and AT style power supplies are no stranger to this. Many supplies will go out with a chirp, hiss and or bang – and this is mainly capacitor related. The electronically handy can get out their soldering irons and replace some of them and pray that there’s no collateral damage. Capacitors can be easily bought from element14, RS Electronics (not so recommended), eBay and other motherboard capacitor stores.

For the lazier sort, you can just buy an ATX to AT adapter which creates the P8 and P9 connectors for AT motherboards by reassigning the wires from the ATX pins.

In fact, even other power supplies can be replaced with an ATX supply if one is creative enough in soldering and patching leads. The ATX standard makes available +12v, +5v, +3.3v rails, as well as a -5v and -12v rail which should cover the needs of most digital logic based devices from the TTL era.

Of note is that more recent ATX supplies complying to ATX 2.0 or greater place higher emphasis on 12v rail current, thus older ATX 1.0-series power supplies may be more suitable for the 5v heavy older machines. This is unlikely to be a problem though, as power requirements for older machines are much more tame.

However, one has to be careful with this because ATX 1.2 made the -5v rail optional, and ATX 1.3 made the -5v rail prohibited. This voltage rail can be important to ISA cards in older machines, so a quick check of the pin 20/white on the ATX power supply should be made before using it with an older AT system through an adapter or by splicing wires.

Unlike simpler AT supplies which power on immediately as power is applied, ATX supplies control their power state with the green PS_ON wire. By shorting this wire to ground, you initiate power-on of the computer. For AT machines, it is as simple as connecting a ground and the PS_ON green wire to one of the poles of the mains toggle switch of an AT case and you’re done :).

Monitors and Graphic Cards

If you’re still running an EGA/CGA graphics adapter, monitors and graphic cards are getting fairly rare. Unfortunately, some games require a particular EGA/CGA adapter, so it’s pretty much a case of conserve. Without it, you’re down to some rather expensive and special active converters – unfortunately, I’ve got no CGA on me, so I can’t comment on it.

But if you can do without, a VGA graphics adapter makes life much easier as the VGA connector, while being phased out, is still widely available on projectors, LCD screens, and CRT monitors. In fact, you can even get adapters which digitize the VGA signal and put it out as HDMI so you can really “keep things trundling along”.

In the case of Sun workstations with 13W3 connector, you can buy an adapter which allows you to connect it to high end VGA multisync monitors (mostly CRTs due to oddball refresh requirements). At least this means you’re not stuck looking for rare and expensive Sun CRT monitors.

Fans and Heatsinks

In general, it’s probably a good idea to clean all heatsinks, remount them with new thermal paste and replace the fans entirely. Most of the fans will be a standard size, so there shouldn’t be as much of a problem to replace them.

In the case of non-standard size fans, there’s not much you can do. Either you replace it with a standard size and use cable ties/twist ties/bluetack or something like that, or you try to keep the existing fan going. If the fan’s already rattling, running slow or squeaking, you can prolong its life slightly by adding light machine oil to the bearings which is underneath the brand label on the fan.


This is a big issue – many of the computers will have special custom form factor sizes and even AT cases aren’t available anymore, so you can DIY your own case, or build it out of cardboard etc. Or maybe integrate it into a MAME style cabinet if that’s what you’re going for.

Floppy Drives

A very important part of old computers – these things fail quite often. In fact, according to the spec sheets on some drives, the heads are really only rated for about 7 days continuous sliding against the media surface, so there’s many chances that the drive in your given machine is intermittent, or somewhat picky due to alignment drift.

An essential thing to do is to clean the heads of drives rather infrequently, but at least once every so often (say after reading a damaged/squeaky disk). It can be simply done with a low-lint kimwipe dipped in high purity isopropyl alcohol and giving the heads a bit of a rub when disassembled. This way, you don’t need to buy expensive cleaning disks which are very unlikely to be available.

You can even repurpose the shell of a defective floppy disk and secure the low lint kimwipe inside the shell perfectly flat and taut and put a few drops of isopropyl on it and activate the drive to seek the head back and forth across the wipe to clean the head.

Also important is to lubricate the rails which the head runs on, and the worm drive gearing which drives the head back and forth. Using something like petroleum jelly or light grease on these parts will keep them running smooth and quiet.

Alignment is a bit of an issue which is hard to fix at home without proper alignment disks service manual and oscilloscope. Using a properly formatted disk from another machine and a few disk copy utilities, you can perform a crude alignment.

RTC Battery

Some machines have a soldered rechargeable battery which may leak – cleaning off corrosion and replacing this is a good maintenance procedure. Others have removable primary lithium coin cell batteries which pose no problem for replacement.

Some have 1/2AA primary lithium cells which will need a quick bit of solder to attach cables to the tabs – these can be available from specialty electronics suppliers like element14.

Finally, there are the nasty sorts like the timekeeper lithium clocks used by Sun machines and Dallas DS12887 RTC which have the battery potted in with the memory. What were they thinking!?! Having the battery which will give up in 10 years is forced obsolescence – and some of these parts are not interchangeable with their “currently still manufactured” equivalents which makes it annoying … and sometimes impossible to fix. It’s also unfortunate that many of them are soldered on board which means that you can’t replace them without a lot of fuss.

Worse still, some systems have some initialization data in the timekeeper RTC module, when replaced with a new blank module, the system is unable to boot or requires configuration with a special program which might be hard to obtain. In the case of Sun, you will need to reprogram your IDPROM as suggested here.

The devices can be reworked in some cases – if you have a dremel tool, you can try this. Such a fix will be useful well into the future, but needs to be done right … otherwise you might be left with nothing.

Keyboards and Mice

For older AT machines, their keyboards used a large circular DIN-5 connector. Modern PS/2 mini-DIN connectors are entirely electrically compatible with the signalling for these older connectors, so it’s a simple case of a wire adapter which you can buy to convert between.

Older AT machines used serial COM ports for mice, so an older ball-style serial mouse will be required and so will a mouse driver. However, while these may be hard to find new, there are heaps of them around so finding an old one lying around shouldn’t be too hard. Unfortunately, many of them don’t support using say a PS/2 splitter and attaching a PS/2 keyboard and PS/2 mouse to the same DIN-5 connector.

As for other more specialized machines like Sun workstations – it’s a bit more desperate. You really do have to get the right equipment, and when you do, never let it go.

Other Tips

Depending on how old your vintage machines are, the difficulty of keeping them alive will vary. But common sense goes a long way to keeping them running for as long as possible – some tactics include:

  • Regular maintenance – cleaning of dust, inspecting the insides for signs of problems before they escalate and cause collateral damage.
  • Reducing use to the bare minimum – as we know, things like CRT tubes wear out over time, and heat can affect semiconductors and degrade them over time, so only using the vintage machines for demonstrations and tests which cannot be done otherwise is sensible.
  • Substitute and upgrade where possible – find adapters to adapt older systems to modern systems as much as possible, and buy them when they’re still available. Store it with the system so you don’t lose it. Or substitute whole subsystems with more modern ones.
  • Collect spares – if you intend to keep the machine for a while, it will make good sense to collect spare parts which are tested to be compatible and working so that when something fails, hopefully you have a spare to keep it running rather than going on a frantic search or giving up. If you have opportunities, especially because someone is discarding even a non-working machine, it could be useful to keep it just to use as a source of donor modules.
  • Store with care – ensure that when in storage, the machine is stored in a low-humidity place so the machine doesn’t corrode, oxidise or rust. Consider sealing it with a desiccant, so that bugs don’t get inside and cause shorts. Remove anything that’s likely to leak catastrophically – e.g. batteries.
  • Backup – it’s definitely a no brainer to make copies of everything. Several copies, on different media, with different drives. Even better, take a whole image of the system disk – for an IDE drive in CHS, some semi-modern motherboards can still handle them when directly connected (USB raptors and docks only support LBA!). With any luck, backing up to enough different types of media, and making copies of the originals will mean there’s enough to get ONE working copy at the end of the day.
  • Document – write down every setting and quirk so you don’t have to rediscover them. Write down the jumper settings, write down the hard disk geometry – once you move that BIOS battery (or if it gets flat), then you would lose it. Make a copy, keep it inside the machine! Even better, take photos of the insides. If you can make a good set of photos, when a component burns out, you can read the value from the photo! Go and make copies of all the documentation you can find, especially if it’s a very unique part or machine.

About lui_gough

I'm a bit of a nut for electronics, computing, photography, radio, satellite and other technical hobbies. Click for more about me!
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