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Fitting the GOTEK FlashFloppy

In previous episodes of the Atari 520STFM refurbishment it was cleaned and recapped. This instalment sees installation of a replacement floppy drive. The GOTEK, sometimes known as FlashFloppy (really the name of the firmware it runs) is a drop-in replacement for a 3.5″ floppy disk drive which has several benefits:

It takes a FAT-formatted USB stick
The computer sees it as a normal floppy drive
It can serve a lot of 720K or 1.44MB disk images from a 16GB memory stick
A tiny OLED screen makes disk selection pretty easy
It’s much faster than a floppy drive

The downsides are that you can no longer use your old floppy disks, and sadly it doesn’t make those nostalgia-inducing head-seek noises… at least my one doesn’t!

There are a couple of different GOTEK models, one old and one newer. The story goes that the price of the disk controller 10x’d so the makers changed it and the firmware wasn’t immediately compatible. My one, bought on fleabay UK, May 2024 has the newer chip.

The drive chassis is approximately the same size as the floppy drive being removed, but this one was found to be fractionally shorter (approx 1cm) so the power cable would not reach.

Power cable fails to reach even at full-stretch

This was resolved by cutting approxiamtely 6cm of floppy power cable from a dead ATX power supply, and soldering four spare header pins left over from an ESP32 project.

A salvaged floppy power connector extension

Naturally shrink-wrap sleeving is never available to hand so some fine purple electrical tape had to do. Hot glue would probably work quite well to secure the header pins as well.

Next come the flyleads for the GOTEK’s rotary controller and OLED display. Not all GOTEKs come with an external control/display – most seem to have the display built in and many only have up/down buttons, not a rotary control at all. Given the drive is on the side of the STFM, the standard display isn’t visible most of the time which isn’t very practical, so the external module seems much more useful. The display needs careful positioning as redoing it later is a PITA.

A small knife was used to very gently pry open one of the slots in the top of the case in order to position the display properly when clipped in. This is necessary because the connector blocks don’t fit through the slot without a little extra encouragement.

Gentle encouragement. Don’t crack the case!

I took a moment to appreciate the colour-coding on the wires and the fact that the connectors on duplicate colours are alternately polarised meaning they cannot be connected incorrectly. That’s super helpful, but countered by the fact these one-pin blocks don’t make very solid mechanical contact, tending to fall out if you look at them wrong. Securing them using small spots of superglue seems to help.

The excess wires are pushed through from the above and the controller/display module is positioned and clipped onto the top of the ST case such that the wires can’t be seen.

Rotary Controller and OLED breakout module

The drive itself has the USB socket very close to the old eject button surround moulding which interferes very slightly but in practice it doesn’t seem to affect USB connectivity. Unfortunately in this configuration, in order to allow the ribbon cable to reach, the drive is technically mounted upside-down.

With everything closed back up it’s quite a smart-looking solution. Pretending to be a floppy drive doesn’t remove the quirks of using floppy disks but it does make them easier to deal with.

Atari 520STFM pictured with Ultrasatan SD virtual hard disk and GOTEK virtual floppy drive

The firmware version shipped on the drive seems fine but it’s possible to flash updates using the FlashFloppy code and documentation here. All in all the GOTEK is pretty easy to fit aside from the extra power extension. I will almost certainly be fitting more in the future.

Atari STFM520 keyboard & case refurbishing

In part three of my ongoing nostalgiathon refurbishing an Atari STFM it’s time to clean up the keyboard and case.

Step one is to remove the keyboard from the chassis – very simple to remove the seven short screws from underneath to release the top-side of the case. The keyboard floats on the shielding and is connected via a delicate 8 pin (7 wired and one polarising blank) header connector. This keyboard wasn’t very grubby – I’ve definitely seen much worse. A little grime and some letraset lower case, plus the usual dust, fluff and crumbs in-between the keys.

Using a keycap puller makes very quick work of removing all the key caps without damaging the switches or support pillars. The Enter and Space keys also have metal stabilisation bars which can be carefully unclipped from the keyboard chassis. Be gentle with these bars – they’re attached to the keycaps using small plastic clips which are easy to bend and break.

All the keycaps soaked in warm water and washing up liquid. These were individually scrubbed with a soft washing up pad, which was enough to remove the grime and the letraset.

The keyboard assembly with all keycaps removed

The keyboard chassis with included light muck. This was wiped first with surface cleaning disinfectant wipes then with cotton-buds and isopropyl alcohol (IPA).

After scrubbing, the water was changed and the key caps were rinsed.

Keycaps were left to dry on kitchen towel. Also visible are the stabilisation bars for Enter and Space on the left, and one of the stabilisation support clips on the bottom.

Whilst the key caps were being cleaned, advantage was taken of a pleasant sunny afternoon. The top case was liberally sprayed with oxyclean peroxide spray (similar to Retrobright) and left in the sun for several hours, respraying and rotating every half hour or so. This can also be wrapped in clingfilm to reduce or avoid respraying.

All the keycaps were replaced using a reference photo taken before disassembly. The stabiliser pivots also had a pinhead of lithium grease applied. I imagine this is only really to reduce squeaking.

Seeing everything reassembled in the case is very satisfying. The top case only suffered slight yellowing which has mostly cleared up now. I’ll have to try it again soon with my other STFM which is much worse.

Installing the Exxos 4MB RAM Atari STFM expansion

In the unlikely event you read my earlier post on recapping the Atari STFM power supply, you’ll know I recently acquired a good example of a mid-late revision Atari 520STFM. Now its PSU has been recapped and cleaned up, it’s time to have a crack at upgrading it from half a megabyte of RAM to 4MB, the most it can take in stock config.

There are several ways to perform this upgrade, from the difficult but reliable desolder all the current RAM chips, source and buy new compatible ones and resolder them, to piggybacking daughterboards of various types, heavily dependent on the motherboard revision in question.

C103253 rev.1 Atari STFM motherboard before expansion

My motherboard is a C103253 rev.1, as pictured so for this upgrade I opted for the Exxos “The LaST Upgrade” MMU piggyback with a stacking board which sits on the shifter chip and connects with a ribbon cable.

Opening up the shielding (centre of image above) revealed a socketed shifter. Apparently this isn’t always the case but it’ll do for me. The shifter chip can be gently pried out of its socket with a thin blade, then inserted into the shifter daughterboard, which I bought fully assembled. This can then be inserted back into the shifter socket, and that part is complete. Next time I do this I’ll consider buying the kit to construct, as it’s not a very complicated assembly.

The shielding doesn’t fit back over the stacked shifter now, which is flagged as an outcome in the documentation. I didn’t want to completely remove the shielding so I opted to bend it over backwards over the video modulator. It just fits now under the main case shielding when it goes back on, which is great, but it does now interfere with the floppy ribbon cable in particular. This makes it awkward to put the original floppy drive back in but might be sufficient with a GoTek as they look a little shorter than the original drive. I don’t have one to test-fit yet so I might need to revisit this shield later.

Next on to the MMU piggyback. The pitch of these pins is smaller and they look very delicate compared to the pins on the shifter for example. This daughterboard sits directly on top of the MMU – its retaining clip needs to be removed – and requires a disconcerting amount of pressure to seat it fully in the socket, as its pins are jammed in next to the socket pins. I chose to pull the motherboard out of the bottom case, seat the daughterboard and carefully push down onto it, and a desk using the palm of my hand and my weight. It felt extremely uncomfortable as I’ve never had to use that much force to seat a chip.

Lastly the old RAM still soldered onto the motherboard either needs to be removed, or disconnected. Doing the latter is much less work and can be reversed later if necessary. The 68ohm resistors R59, R60 and R61 need lifting to 5V. On this motherboard this means desoldering and pulling the right-hand-side legs, closest to the MMU then adding a jumper wire over to the +ve leg of the 4700µF capacitor adjacent on the motherboard.

Use solid core wire, not like I did here

The result is a 4MB STFM (woowoo!) which boots to desktop and as yet has no way to run software because the flopy drive is dead and I haven’t formatted any SD cards for the ultrasatan yet (and will that even work with TOS 1.02?). Haha.

All parts were sourced from Exxos, with advice from the Atari ST and STe users FB group.

Installing the Exxos Atari ST PSU recap kit

I recently acquired a classic 16bit machine from my childhood in the form of a Motorola 68000-powered Atari 520STFM. Whilst it’s a later motherboard revision – C103253 REV.1 – it’s still a low-spec model with only 512MB RAM. The “F” in STFM is for the included 3.5″ floppy disk drive with the “M” being for the built-in TV modulator.

My hope is to upgrade this machine to the maximum of 4MB RAM and see which other add-ons (e.g. GoTek USB-stick floppy drive replacement; ultrasatan SD-card virtual hard drive; TOS upgrades; PiStorm accelerator) will best modernise the experience.

But first things first, I know enough to not turn it on in excitement – the most common fault with these older machines is failing electrolytic capacitors as the paste in them dries out, particularly in hotter environments like power supplies, so let’s have a look at the PSU… This model is a common Mitsumi SR98. We’re looking for bulging capacitor packages like this one.

The Exxos PSU refurbishment kit includes a replacement set of capacitors, a couple of replacement resistors and modern, more-efficient rectifier and low voltage schottky diode. This results in improved stability, improved ripple and lower temperatures. It’s also well within my soldering abilities!

The Exxos refurbishment kit, as it comes

Mitsumi SR98 PSU as it came, with replacement targets highlighted.

The fiddliest part is easily the rectifier as the new one is significantly larger and a different shape, but once it’s all done it looks something like the image below. A quick visual inspection underneath for bridged tracks and stray solder, maybe a quick clean with isopropanol and a toothbrush, and it’s ready to go.

The refurbished PSU is refitted carefully back into the case and reconnected to the low voltage header on the motherboard. Various parts of the PSU are mains live when turned on (danger of death!), so extreme care needs to be taken if the whole case isn’t reassembled. Also note that this PSU likes to be loaded – i.e. not to be run bare, so don’t turn it on without plugging something in (ideally a cheap bulb, rather than an expensive motherboard).

Using a multimeter I measured the voltage across the large 4700µF capacitor and trimmed VR201 down slightly to bring the voltage closer to 5.00V.

Now flipping the power switch results in a little green desktop and no magic smoke!

This booted without a keyboard, mouse or floppy drive. I used an RGB SCART cable to an OSSC scan doubler (middle right), then HDMI to a regular modern monitor. The image in both low and medium resolutions is crisp and clear with very little hint of instability.

Next steps: cleaning the keyboard, retrobrighting the case, upgrading the TOS ROMS, fitting the 4MB RAM upgrade, Gotek and ultrasatan drives.

All the information I used for this PSU refurbishment was from the Exxos Forum.

Technostalgia

Ahhhhh, Technostalgia. This evening I pulled out a box from the attic. It contained an instance of the first computer I ever used. A trusty BBC B+ Micro and a whole pile of mods to go with it. What a fabulous piece of kit. Robust workhorse, Econet local-area-networking built-in (but no modem, how forward-thinking!), and a plethora of expansion ports. My admiration of this hardware is difficult to quantify but I wasted years of my life learning how to hack about with it, both hardware and software.

The BBC Micro taught me in- and out- of the classroom. My primary school had one in each classroom and, though those might have been the ‘A’ or ‘B’ models, I distinctly remember one BBC Master somewhere in the school. Those weren’t networked but I remember spraining a thumb in the fourth year of primary school and being off sports for a few weeks. That’s when things really started happening. I taught myself procedural programming using LOGO. I was 10 – a late starter compared to some. I remember one open-day the school borrowed (or dusted off) a turtle

Brilliant fun, drawing ridiculous spirograph-style patterns on vast sheets of paper.

When I moved up to secondary school my eyes were opened properly. The computer lab was pretty good too. Networked computers. Fancy that! A network printer and a network fileserver the size of a… not sure what to compare it with – it was a pretty unique form-factor – about a metre long, 3/4 metre wide and about 20cm deep from memory (but I was small back then). Weighed a tonne. A couple of 10- or 20MB Winchesters in it from what I recall. I still have the master key for it somewhere! My school was in Cambridge and had a couple of part-time IT teacher/administrators who seemed to be on loan from SJ Research. Our school was very lucky in that regard – we were used as a test-bed for a bunch of network things from SJ Research, as far as I know a relative of Acorn. Fantastic kit only occasionally let down by the single, core network cable slung overhead between two buildings.

My first experience of Email was using the BBC. We had an internal mail system *POST which was retired after a while, roughly when ARBS left the school I think. I wrote my own MTA back then too, but in BASIC – I must have been about 15 at the time. For internet mail the school had signed up to use something called Interspan which I later realised must have been some sort of bridge to Fidonet or similar.

We even had a networked teletext server which, when working, downloaded teletext pages to the LAN and was able to serve them to anyone who requested them. The OWUKWW – One-way-UK-wide-web! The Music department had a Music 5000 Synth which ran a language called Ample. Goodness knows how many times we played Axel-F on that. Software/computer-programmable keyboard synth – amazing.

Around the same time I started coding in 6502 and wrote some blisteringly fast conversions of simple games I’d earlier written in BASIC. I used to spend days drawing out custom characters on 8×8 squared exercise books. I probably still have them somewhere, in another box in the attic.

Up until this point I’d been without a computer at home. My parents invested in our first home computer. The Atari ST. GEM was quite a leap from the BBC but I’d seen similar things using (I think) the additional co-processors – either the Z80- or the 6502 co-pro allowed you to run a sort of GEM desktop on the Beeb.

My memory is a bit hazy because then the school started throwing out the BBCs and bringing in the first Acorn Archimedes machines. Things of beauty! White, elegant, fast, hot, with a (still!) underappreciated operating system, high colour graphics, decent built-in audio and all sorts of other goodies. We had a Meteosat receiver hooked up to one in the geography department, pulling down WEFAX transmissions. I *still* haven’t got around to doing that at home, and I *still* want to!

Acorn_A3000 — Acorn A3000 Publicity Photo

atari-ste-turbo-pack — Atari STE Turbo Pack

The ST failed pretty quickly and was replaced under warranty with an STE. Oh the horror – it was already incompatible with several games, but it had a Blitter chip ready to compete with those bloody Amiga zealots. Oh Babylon 5 was rendered on an Amiga. Sure, sure. But how many thousands of hit records had been written using Cubase or Steinberg on the Atari? MIDI – there was a thing. Most people now know MIDI as those annoying, never-quite-sounding-right music files which autoplay, unwarranted, on web pages where you can’t find the ‘mute’ button. Even that view is pretty dated.

Back then MIDI was a revolution. You could even network more than one Atari using it, as well as all your instruments of course. The STE was gradually treated to its fair share of upgrades – 4MB ram and a 100MB (SCSI, I think) hard disk, a “StereoBlaster” cartridge even gave it DSP capabilities for sampling. Awesome. I’m surprised it didn’t burn out from all the games my brothers and I played. I do remember wrecking *many* joysticks.

Like so many others I learned more assembler, 68000 this time, as I’d done with the BBC, by typing out pages and pages of code from books and magazines, spending weeks trying to find the bugs I’d introduced, checking and re-checking code until deciding the book had typos, but GFA Basic was our workhorse. My father had also started programming in GFA, and still did do until about 10 years ago when the Atari was retired.

Then University. First term, first few weeks of first term. I blew my entire student grant, Â£1400 back then, on my first PC. Pentium 75, 8MB RAM, a 1GB disk and, very important back then, a CD-ROM drive. A Multimedia PC!
It came with Windows 3.11 for Workgroups but with about 6 weeks of work was dual boot with my first Linux install. Slackware.

That one process, installing Slackware Linux with only one book “Que: Introduction to UNIX” probably taught me more about the practicalities of modern operating systems than my entire 3-year BSc in Computer Science (though to be fair, almost no theory of course). I remember shuttling hundreds of floppy disks between my room in halls and the department and/or university computer centre. I also remember the roughly 5% corruption rate and having to figure out the differences between my lack of understanding and buggered files. To be perfectly honest things haven’t changed a huge amount since then. It’s still a daily battle between understanding and buggered files. At least packaging has improved (apt; rpm remains a backwards step but that’s another story) but basically everything’s grown faster. At least these days the urge to stencil-spray-paint my PC case is weaker.

So – how many computers have helped me learn my trade? Well since about 1992 there have been five of significant import. The BBC Micro; the Acorn Archimedes A3000; the Atari ST(E); the Pentium 75 and my first Apple Mac G4 powerbook. And I salute all of them. If only computers today were designed and built with such love and craft. *sniff*.

Required Viewing:

Micro Men
The Pirates of Silicon Valley