News are slow lately and I’ve been told some people find old electronics interesting – so I’m going to present one of my latest “experiments”. It’s mostly to brag but but if you find it useful, all the better.

I’ve bought several 386 mobos, each cost me about 10 Euros (and a couple more for shipping) and all were described as dead, not booting. Nothing really surprising about it, pretty much all of these have old NiCd battery on them and those are notorious for spilling their guts and corroding the copper – sometimes to the point where the traces and vias are completly gone. If you ever get one of these, and the battery has not beeen removed or replaced, desolder it ASAP.

Here’s the seller’s photo, all in all the mobo looks in pretty good condition but you should be able to spot the greenish corrosion already:

The spill wasn’t that bad – water+brush, vinegar+brush, water+brush, and the PCB started looking way better. Actually there weren’t any broken connections but some solder joints and traces were corroded to the point where I decided to rework them. Better to spend 15-30 minutes now than hours later figuring out why things randomly don’t work.

If you paid attention you noticed one of the plastic support pegs was still in the board when it was sold. Turns out there is a reason for it, it’s a very tight fit and I had some serious trouble removing it. I’d just cut it off, if it wasn’t for the fact these old pegs come in handy if you want to put the mobo inside an AT case. But apparently I wasn’t the only one who tried to remove it and someone before me was not as careful with their tools. There were deep scratches on some of the traces near the hole, and I’ve decided to remove the solder mask there and tin those over to make sure there is proper electrical connection. Again, I’d do it even if the trace showed continuity, these are ISA bus signals and there has to be enough copper on each connection to allow proper currents. Otherwise the rise/fall times are going to be absymal and that’s just asking for trouble.

I mean, look how close those traces are to the hole – right on the edge. Who designed this thing?! I could fix it in 10min in the CAD by moving some of the bottom traces to the other side, and then repositioning the hole itself a bit. I think I could get 1mm clearances on both sides without actually re-routing anything. Still not a lot but at least something. Seriously, that’s a bad job.

Alas, that wasn’t all that was wrong with this motherboard. Notice that crystal in the bottom right coner? It’s not soldered in at an angle. It’s actually sheared off, stopped only by the capacitor that got a bit damaged in the process as well. That had to be replaced but it’s easy – if you have the parts. I didn’t so I’ve replaced it with 14.7456MHz and now it’s a bit overclocked mobo.

Does it work now? It does! That is, after I’ve put on some missing cache size jumpers.

That’s a seriously impressive BIOS for such a cheap mobo. Or so I thought. Well it turns out the BIOS has quite a few options that the motherboard / chipset doesn’t actually support. When I was trying to map the PGA132 socket connections I noticed that A20M# signal is indeed connected – but only to the keyboard controller. Not to the chipset. So how does a Cyrix CPU work with “Fast Gate A20” set to enabled? Maybe it doesn’t. Or maybe the “Fast Gate A20” option can’t be set at all, becasue it’s not supported, as I’ve learned few hours later.

It’s required to turn off the Turbo Switch function if you don’t have an actual switch connected – because it defaults to slow. A minor annoyance but took me 15 minuts to figure it out. I thought my test card was somehow slowing down ISA but to a crawl.

UPDATE: Forgot to mention this but the ISA clock setting of 14.3181/2 doesn’t work either. At least it’s easy to spot, the mobo will just freeze with speaker tone on, during boot. Only CLK2 dividers work and there’s not a lot of them so for 20MHz bus you will get a lousy 6.67MHz ISA clock.

You can set the Cyrix CPU to BARB or FLUSH but the FLUSH# input is not connected at all. So BARB it is. I’m still unsure if the mobo properly supports the hidden RAM refresh (forgot to check with the scope, will do it later) but at least there is a performance difference between L1 off and L1 on with BARB enabled. So it might just be working properly and not flushing the cache every 15us. But the whole purpose of this project is to experiment with the FLUSH# input anyway so it’s not a huge deal either way.

Well then, time for the mod:

The mobo does have an empty space for PGA132 socket but apparently it was supposed to have either the socket, or the PQFP CPU soldered in. Not both. So there is no jumper to disable the PQFP CPU and I had to solder a wire to FLT# input myself – though at least the empty space for the alternative clock generator and it’s two jumpers allowed me to easily add a jumper of my own. Then I’ve soldered in the socket and put in the Cyrix. And what do you know, it works well.

That was about 20 Euros in parts and a whole afternoon of work but now I can easily test PGA132 CPUs wihout having to mess with the FM Towns machines. I can do most testing and code dev on this PC. There is no 16MHz clock selection but there is (undocumented) 20MHz and it seems my 16MHz CPUs work at 20 as well. I could aways add a clock divider to the 33MHz setting but that would require more work and with high frequency signal (66MHz to be divided by 2) which is always tricky. Might not work with just wires and so I’d have to design some sort of add-on PCB to stack over the clock amp 74F gate – not that difficult but it’s more time and money spent. So I’d rather not.


I’ll be shipping whatever Type-3 Phoebes I still have in stock next week, and after that there will be a short pause until I get the next Phoebe batch. So if you don’t get payment request next week you’ll have to wait until the first week of March, or so.

Same goes for any DocBrowns I haven’t shipped yet. There was a delay with the parts I ordered and now the batch is about 3 weeks behind schedule. On the bright side those will come with 1.5.1 FW that has the Flash corruption issue fixed for good. Though if you had this problem with 1.5.0 and you haven’t recapped your Marty PSU yet, I’d recommend looking into it sooner rather than later. In general these PSU hold up rather well for their age but the electrolytic caps are probably only barely within specs by now.

Speaking of FM Towns, I’ve found some TI docs that nicely explain what external circuitry the 486SLC-class CPUs need to have proper cache flushing support. Considering that replacing the 386 with 486 usualy involves soldering anyway, additional wire or two and an extra 74AC chip wouldn’t really be that much of a problem and it just might simplify a lot of things on the modded system. I need to investigate.

It would be much easier (and cheaper should I mess up) to experiment on a typical PC mobo though, and so I’ve obtained one that looks like it can actually support 486SLC chips natively. But the clock is hardwired to 40MHz for the AMD 386SX that’s on it – and while it’s not terribly difficult to mod it to a different clock speed with external generator, I’m not sure if it’ll work properly with the memory and ISA bus. Chances are those have to be synchronized with the CPU clock.

So, if there’s anyone with a TX486SXLC-040 chip in PQFP-100 package for sale, I’d be very interested in buying it. Or trading for some ODEs if that’s preferable.

UPDATE: Forgot to make a photo of the mobo:


Okay, I didn’t want to do politics here but there are a few things that need addressing.

First, there is this shutdown in USA that apparently has quite an impact on the swiftness of customs procedures. Or, to put it bluntly, lack of thereof. Please keep that in mind while waiting for the packages to arrive – some might be delayed quite a bit. That being said, once 3-4 weeks have passed do inquire at your nearest postal office every week or so, I’ve just had a few envelopes returned to me with “unclaimed” sticker and apparently there weren’t any notices delivered. Although that was probably due to the Xmas rush and sales after – but it might get worse.

Second, after today’s vote we are looking at a no-deal Brexit being the most likely outcome for the UK. The problem here is nobody can tell me what that will do to postal services. Customs aside, there is even some confusion as to whether or not the stamps will be valid and of correct value. So, to avoid any problems I will cancel any UK orders that I can’t ship in time. Again, that is only in the case of no-deal, and even then hopefully only a temporary restriction until things settle down.

With that out of the way, I will be opening orders for DocBrowns on this Sunday around 12:00 CET (my Saturday will be too busy for that). I don’t expect to get many of those so Sunday doesn’t seem that bad of a choice. I have very limited stock but I can make more in few weeks time. Still, to give actual Marty owners a better chance of getting one you will be asked to provide your console serial number – so have that prepared. If you choose not to, you will be moved to the end of the list and if there are too many orders I reserve the right to just cancel those without the serial number. You will find the number in question in the SRAM card bay below the floppy drive.

Lastly, I plan to have Phobe orders open on the last Saturday of this month but I will edit this post in a week or so to confirm that – I need to ship most of the Rheas before I take on more orders.

PS. Please keep the comments civil.

UPDATE: Phoebe orders will open this Saturday, around 12:00 CET (as in noon for the am/pm users).

UPDATE 2: Phoebe list is full, there was rather unexpected surge of orders even though the last Phoebe sale was some 2 months ago, and that was a big one too. Give me few days to compile the list and send confirmation emails.

Holding Back the Years

Just to clear any possible misunderstanding, there WILL NOT be a Phoebe ordering window this Saturday. Most likely it’ll happen at the end of January, after I’ve shipped most/all GDEMUs. So Marry Xmas and Happy New Year everybody, we’ll see each other in 2019.

As for the photos below, this is a personal project and I won’t go into details – enjoy, or not, it’s not an ODE and has nothing to do with my other devices. I just wanted to share it since now (after many years) it’s done and I can close this chapter for good.

Running in the 90s

I’m still quite busy – I’ll spare you the details and instead offer a revised plan of action. It’s December now and I wish to avoid shipping anything I don’t have to until 2019, for three reasons:

  1. It’s a waste of time, it’s Xmas shopping spree already and post office queues are huge.
  2. Due to Xmas and Black Friday related online purchases delivery times are longer as all shipping channels tend to saturate until late January or so.
  3. All of that increases the chances of the packages getting damaged or lost in transit.

I will probably make exception for the current DocBrown orders, I have it all ready except I’m still considering bigger envelopes. The very first batch arrived intact though… Well, I’m going to make that decision in the next few days.

Now, just because I’m not shipping anything this month doesn’t mean I can’t take orders and prepare for January. In fact I’m already stockpiling devices for that very purpose. So next Saturday I will open orders for GDEMU, and then, on the Saturday after that, for Rhea. I have Phoebes too but seeing how I just ended shipping those I belive it’s time to give other devices a chance to sell. That being said, if the GDEMU or Rhea orders are small enough I might consider offering more Phoebes this year still. We’ll see.

In the meantime I amused myself modding Sega Master System console I found on sale for about 10$. As far as I can tell it was never worked on, and some plastic wear aside it’s in a good condition. Just what I like, a few scratches (which are non-issue to me) and a low price. I recapped it, removed the TV modulator and changed some parts around the video encoder to have it output RGB, audio and composite signals with correct impendance. I’m no pro modder but I think the end result is pretty nice:

Oh, and one last thing: While I’m reading all the emails I get, I have not responded to anything that’s not urgent and/or support related. That being said not all of us are native English speakers and sometimes we don’t get our point clearly across so if I didn’t reply but you do actually need my help, please email me again.

UPDATE: GDEMU orders are now open closed again. If you missed it don’t worry, there will be more late January (or so).

UPDATE 2: Rhea orders are now open closed.

Walk Like An Egyptian

All Rheas are shipped, finally, and I’m now testing and packing the outstanding Phoebes. If all goes well I should have that all done next week so if you’re still expecting a payment request this is the time to pay attention to your email and PayPal account.

Speaking of PayPal – it seems to have glitched yesterday and some requests were duplicated (or even triplicated). I can actually see that on my side too but this is not the first time it happened (although usually it’s just one request that glitches, not all of them) and from experience cancelling one tends to remove all the copies along with it. So then I have to issue another one.

To work around it pay one and then cancel the rest on your side – this way at the very least I get a “It’s been paid” entry with your address so I can proceed with shipping as usual. If that doesn’t work for you for some reason (the glitched requests sometimes refuse to accept payment) please contact me by email to sort it out.

The Eternal March

If you didn’t get your Phoebe payment request by today you will have to wait some more. Worst case is 3-4 more weeks. We had some production delays and I’m short on Type-2 devices, as well as a couple of Type-4. This however serves as a reminder, to me, why I should never do the long queues you people constantly ask for. You have no patience. And I have none to spare.

What I do have is some Rheas since we usually make both Saturn ODEs at the same time. I will open orders this weekend though I fully expect it will turn out just like Phoebes did – the emails will be delayed and I’ll get flooded with too many orders. I’ll decide how to tackle it once I have a full picture of the disaster.

Note that I am very busy ATM and will be during this whole month. Spamming me with “is it ready yet” messages annoys me so I’ve started to ignore those.

Oh and as for DocBrown, I’ll start shipping those out soon. I’m working on something related and was hoping to have it ready by now, and I kind of do but it needs more polishing. So there is no point in futher delays, the current menu software works well enough as-is.

UPDATE: Rhea orders are now open closed.