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What RAM slots are these?

I recently found a relic on eBay. It's an AST Bravo 4/33 (not the LC!) and has a very proprietary motherboard. I'd seen the photos and I thought I saw standard 72-pin SIMM slots. Turns out I was totally wrong... I've never seen this size before!? There's a similar-but-not-quite motherboard diagram here, but the jumpers are in different locations. The strange RAM also doesn't get a mention?

Turns out they're neither 30-pin, nor 72-pin! Did AST decide to use Apple's proprietary 64-pin SIMMs? There are similar (68-pin) 256kb and 512kb SIMMs on eBay, but they don't match the pin-count and they're for VRAM in older Apples? There also seems to be other something resembling RAM soldered onto the motherboard, but I can't find any information to determine if that's actually RAM or just cache. Either way, the machine just beeps once when power is applied. The beep sounds like a standard "NO RAM" boot error. There's also a fried electrolytic capacitor.

...Actually, I just found two 64-pin 4mb SIMMs for an Amiga... Let's see if they work when/if they arrive...

ASUS Media Bus (aka not-PCI-64-bit)

I'd picked up an old motherboard from an eBay auction and had seen a PCI slot with an extension.

Here I was thinking it was PCI 64-bit...

I grabbed the 64-bit SCSI card that I'd installed in my G4 Graphite Macintosh (which has a suite of 64-bit slots) and quickly realised it wasn't what I thought it was!

Ok.. it doesn't fit... let's look closer?

From the photos above, it doesn't take a genius to work out that it's actually a Media Bus 2.0 slot by ASUS. Turns out they tried, for a short while, to make their own proprietary slot that combines PCI and ISA. The brown socket is actually just a condensed ISA slot and the cards that fit are usually dual-purpose, combining video and sound or SCSI and sound.

V1.2 and V2.0 Compatiblity

Note that there are two versions and I failed. I went gung-ho and purchased an 'ASUS Media Bus' card on eBay without paying attention to the version. This card was meant to be the ATI Mach 64 + Sound Blaster card and I was really happy... saving slots it a great idea! A week after purchase, whilst the card was still in the mail, I did a little more research and realised that this card would be ASUS Media Bus 1.2, not 2.0! I went back to the seller and found a SCSI + Sound for Media Bus 2.0 and ordered that too.

A few weeks later (thanks to surface mail), a missed-delivery slip appeared in my letterbox and I went to pick up the video+sound card...

Sound? Check! Video? Nope... What? The card I had ordered second arrived first! This can't be good. I still had a V1.2 card in-flight somewhere... would it arrive? I purchased a V1.2 motherboard I saw on eBay anyway; it was cheap and I wanted to use this card... when it arrived!

Anyway, back to this card: It's the PCI-AS300 Adaptec AIC-7880 SCSI + Vibra 16 PnP Sound.

It fits nicely, as one would expect... and works perfectly too!

The V1.2 motherboard then showed up (before the V1.2 card!) and, just to test, I tried to see if the PCI-AS300 would fit...

Nope... millimetres out! I actually think the V1.2 card is lost and I now have a nice and clean Pentium board for another machine... oh wells... Note that the V1.2 slot just says MEDIA whereas the V2.0 says MEDIA BUS 2.0.

I hope others don't make the same mistake!

INTERLINK – Reverse-Engineering the Protocol

I've recently been playing with INTERLINK. Firstly, it was between two real machines, but then I managed to get DOSbox to talk to another DOSbox instance and a real physical PC. From here, there was a thought... why need DOSbox to host the INTERLINK server when I could possibly emulate the conversation and then create an app that'd work on all versions of Windows (or other OS') and then allow easier serial transfers to older equipment.

This post will be a work in progress for quite a while. I'll be updating it as I find time to work through the 'conversation' between the hosts... I might also spend a little time on reversing the actual source of INTERLINK itself.

Snooping in on the Conversation

As per the previous post, I created a quick .NET app to listen in to the serial conversation. This was done via the help of Eltima's Virtual Serial Port Driver. A pair of virtual ports was created and DOSbox was hooked onto one side. From here, I hooked my app onto the other side of the virtual pair and then into the real physical port. A real computer was then hooked onto the end of that port. You could also use two DOSbox instances here, along with two pairs of virtual ports.

You can download the source of my serial snooping app here.

The Conversation

This is where it now gets a LOT harder. Below shows the client (green/left) talking to the DOSbox server (blue/right). From the conversation, the client works out what drives are shared: A: and C: to D: and E:.

The grey boxes are my annotations for what I believe is occurring. More will be added as I work it all out.

DOSBox – Serial INTERLINK to Another PC

So, I recently had Interlink running between two REAL machines. It occurred to me though: Wouldn't it be cool if we could use a USB-Serial adapter on a newer machine and use Interlink from DOSBox to transfer out files? You could then copy anything into the DOSBox HD and get it onto your vintage unit. Great if you have no network, CD or are just sick of unstable floppy disks!

The requirements

DOSbox happily talks to real COM Ports. We'll want DOSbox running real DOS, so follow a guide like Transmission Zero has here to install DOS to a read HDD image. Firstly, download an SVN build of DOSbox. Then download the 256mb image and get your DOS disk images here. After copying everything into the dosbox folder, grab the dosbox configuration from your user profile (you might have to boot DOSbox up once first!) and bring it over as well. I renamed the disk images to make it easier and then edited the configuration as follows:

[autoexec]
imgmount 2 "hdd-256mb.img" -size 512,63,16,520 -fs none
boot .\D1.IMA .\D2.IMA .\D3.IMA

Run DOSbox and you should be presented with the DOS installation screen. Use CTRL-F4 to rotate through disks. Finally, you should be at the DOS prompt!

Serial Ports

Now for the serial configuration. First up, I'm going to show you a neat trick to get everything tested and working. We're going to use a virtual serial port between two instances of DOSbox to prove that Interlink works in the emulated environment. There's a plethora of virtual com ports available for Windows and they all vary greatly... officially I want data to flow from one COM port to another virtual COM port, so I'll need software that'll do this; you'll find that a lot just want to send data over a network. If you have Windows XP or lower (Windows 7 might still work also), then use com0com. Otherwise, if you need signed drivers then Eltima's Virtual Serial Port Driver is pure magic... but expensive. You get a 14-day trial with the standard version, so plan ahead and use it as much as possible! I've actually sent out a plea for help, asking for a cheaper license for just a single 'null-modem' serial port.

So, you've installed a pair as the above picture. To get here you simply installed the VPSD and chose all default values. You now have a COM1 and COM2... or maybe you have COM20 and COM21... (my laptop has no REAL comports, so COM1 and COM2 were available) regardless, we need to edit the configuration (as per the DOSbox manual) of your DOSbox instance and update the serial1 line to:

serial1=directserial realport:com1

Save it, close it and run dosbox. You should see one connection on one of the virtual ports in the port configuration application...

Whilst DOSbox is running, edit CONFIG.SYS and add the line DEVICE=C:\DOS\INTERLNK.EXE to the bottom. Once this is done, close DOSbox and copy the entire folder to a new folder. Rename this to server, or somesuch. Go in and edit this configuration to point to the second comport of your virtual two.

From here, you can boot up both DOSbox's and see that they connect to either side of the virtual com ports. You can then run INTERSVR from the prompt of one node and INTERLNK from the prompt of the other and you'll then connected! Totally pointless... but we've proven that Interlink via serial port works in DOSbox!

Intercepting data...

Just in-case I wanted to spy on the data, I thought I'd try something quickly with C# and the SerialPort class. I set up two pairs of com ports, connected DOSbox #1 to COM1, DOSBox #2 to COM4 and limited their speeds to 9600. I then used the following code to write a quick WPF app to see if I could get the data to traverse...

	<Grid>
		<Grid.ColumnDefinitions>
			<ColumnDefinition/>
			<ColumnDefinition/>
		</Grid.ColumnDefinitions>
		<TextBox Grid.Column="0" Name="FromText" TextWrapping="WrapWithOverflow"></TextBox>
		<TextBox Grid.Column="1" Name="ToText" TextWrapping="WrapWithOverflow"></TextBox>
	</Grid>

That's the WPF, just two text fields to see the data... then the c# to hook it altogether...

	public string FromData { get; set; }
	public string ToData { get; set; }
	private SerialPort port1 = new SerialPort("COM2", 9600, Parity.None, 8, StopBits.One);
	private SerialPort port2 = new SerialPort("COM3", 9600, Parity.None, 8, StopBits.One);
	public MainWindow()
	{
		InitializeComponent();
		port1.DataReceived += new SerialDataReceivedEventHandler(port_DataReceived);
		port1.Open();
		port2.DataReceived += new SerialDataReceivedEventHandler(port_DataReceived);
		port2.Open();
	}

	private void port_DataReceived(object sender, SerialDataReceivedEventArgs e)
	{
		var port = ((SerialPort)sender);
		byte[] data = new byte[port.BytesToRead];
		for (int b = 0; b < port.BytesToRead; b++)
		{
			int fromPort = port.ReadByte();
			data[b] = (byte)fromPort;
		}
		if (sender == port1)
		{
			port2.Write(data, 0, data.Count());
			Dispatcher.BeginInvoke((Action)(() => {
				FromData += " " + BitConverter.ToString(data).Replace("-", "");
				FromText.Text = FromData;
			}));
		}
		else
		{
			port1.Write(data, 0, data.Count());
			Dispatcher.BeginInvoke((Action)(() => {
				ToData += " " + BitConverter.ToString(data).Replace("-", "");
				ToText.Text = ToData;
			}));
		}
	}

Starting the app saw the relevant COM ports fire up in the port configurator... then I booted DOSbox:

Hahaha... it's 99% working. I wonder how hard it'd be to disect the entire chat and build an emulator. I had to limit everything to 9600 as my code doesn't auto-negotiate the speed. Without the limits, the client Interlink was speeding up to 115200 BAUD and the server had no idea what was going on.

I'll dig into those bytes in another post... the data looks pretty simple and might be easy to emulate... anyway... what was the point of this post? Oh yeah!

Talking to real metal

Back to that 286 from the previous post about Interlink. Let's talk to it! This time, instead of virtual ports, we're going to talk to real ports. I've got a USB Serial port which will help out a lot here.

I used this recently when talking to the Apple II. It's always good to know that things work before mucking around with them. I also ended up using the real serial port on my main desktop. Either way, any serial port will work.

Install your COM port and make sure your DOSbox configuration is correct as per the hardware port number. Mine is COM1 on this main desktop.

serial1=directserial realport:com1

Then simply boot up as you've done before with DOSbox. This time the client (or server) will be over the real wire.

Crikey! It just-worked(tm). The laptop happily saw the data in DOSbox. Easy file transfers! I wonder if I can make a Windows app that'll just let you share a drive?!

DOS – Serial File Transfers

This was meant to be easy... I was building a 386 for sale on eBay and had a spare 286 laptop hanging around. I was also selling a 4-metre NULL-MODEM cable which I wanted to list as 'tested'.

First, a warning: Don't let the magic smoke out

There's an age-old notion of magic smoke. This smoke is contained in electronic components and, most importantly, needs to stay inside them. Usually the mistakes of an impulsive, rash, impatient user will cause the smoke to escape. Once it has, there's usually no going back... or if there is, then you'll be spending a lot of time/money trying to get back to the spot you were at prior to the damage.

In this case, I did it to the old 286 laptop used below. On the back of the machine, there's two female DB-25 ports. They're not labeled and I thought I was simply in luck! They've already put a correctly oriented serial port (COM2) on there for me!

Turns out not... turns out one is the printer port (duh!?) and the other is for an external floppy drive. Regardless, I plugged my null-modem cable into the printer port and one electrolytic capacitor started cooking. I turned everything off quickly and inspected the damage. Yup, just one black capacitor (it was meant to be orange!) Unfortunately, when I powered the unit up, the capacitor kept cooking! Currently I've just disconnected it... could just be that that cap was shorted or reverse-polarised and fried... could also be that the whole LPT1 port is dead... gonna be hard to test.

Anwyay... I later found the part that labeled the ports... DOH! Where were we?...

InterLink

Would you believe that DOS 6.0+ came with serial transfers as standard? There's an application in-built known as INTERLINK. From here you just set one machine as the server with INTERSVR.EXE and the other as the client with the INTERLNK.EXE application itself.

The basic idea is to load the INTERLNK.EXE as a driver first, in CONFIG.SYS. You can configure extra options here, but if your connection is correct then it should just-work(tm).

Cabling

The best method is to use a specific printer cable, affectionately known as a LapLink cable. This is a cross-over cable for printer ports and is only used for transferring of files. The next best bet is a null-modem cable which does the same thing, but via the serial port, and supposedly slower as there are less data lines.

We're going to use a null-modem serial cable today and you'll find any number of methods for creating one. You can get adapters that'll convert a standard serial cable, entire cables that are 'null-modem' or you can just create your own.

I had actually picked up a 4-metre 'null-modem' cable from a misc eBay auction and wanted to try it out. This had a male plug on one end and a female on the other and didn't quite make any sense. Hence it allowed me to plug it into the wrong port on the laptop (as mentioned above) and wreak havoc. After that little mishap, I decided to just use other spare parts and rig up my own.

I've spoken a bit about serial cables before, but the basic idea is that there's a DTE and DCE end. It's a standard client-server relationship. In our case, our servers need to talk to eachother, so we need to adapt then of of a cable to allow it to connect. The goal is to cross over the transmit and receive lines to have data transfer correctly. There's also some supporting wires to allow data-handling negotiations to take place. You'll find all the wiring methods on the Wiki page.

Somehow, I found both a female DB-9 and DB-25 in the junk box and followed the first diagram on the wikipedia page. It was only three wires, GND from 5-7, RX from 2-3 and RX from 3-2.

For the life of me, I couldn't get this to work. Interlink just wouldn't see the other end of the cable. I then tested both ports (just to see if I'd fried more parts in the laptop) with a serial mouse and everything worked fine. From here, it must be the cable, right? Maybe it needs to be more fully-fledged with the other data/signal lines linked up. This site seems to indicate further handshaking is required.

I browsed back to the null-modem page on Wikipedia to work out the other wires to hack together. Something then occurred to me... the DB-29 port has RX and TX the other way around! Why would they do this? Regardless, I simply disconnected my taped and twisted wires and ran 2-2 and 3-3 through directly.... the result? Success!

Configuring Interlink

Before you even think of entertaining this idea, make sure your ports are tested functional with a mouse and that you've gone over your wiring 16 times prior. Make sure you've re-read your serial port pinouts and that you have traced each wire. As mentioned above, the DB-25 RX and TX lines are swapped when compared to the DB-9 pinouts!

Once you're feeling game, edit CONFIG.SYS on both your machines and add the line DEVICE=C:\DOS\INTERLNK.EXE on BOTH server and client! At this stage, you can reboot the server. It'll boot up and will spit out a little 4 line message indicating that it's loaded the driver, what disks are mapped and what printer ports are mapped. It'll also tell you that no connection is available. Once at your command prompt, run INTERSVR.EXE. You'll be presented with a pretty boring screen indicating the current activity.

Now, return to the client and reboot it after saving changes to CONFIG.SYS. When this one boots up, you'll hope to see that it's connected. Initially I didn't and it just tells you in CAPS that no connection is available. At this point, it's actually checked all of your ports for a server. This is both your printer and COM ports, so it actually really means that it couldn't find a server! I had this a lot at the start and began fine-tuning the configuration, attempting to limit it to a single com-port with /COM:2 switches... but it ended up being my cable!

Once you're up though, it's all easy! As per below, you'll be told what drives/ports are mapped and it really is as easy as just switching to that drive and listing directory contents, or copying from them!

I pulled over A-Train (quite quickly, actually!) and tried to run it on the 286 Laptop... it's not VGA, so we didn't get far at all. But it's a 286 without VGA, what was I expecting? Might need to try Railroad Tycoon... I wonder if I can Interlink that over from DOSbox?