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68-pin RAM SIMMs

I had previously picked up this Bravo 4/33 486 Machine and had assumed, from the photos in the auction, that it needed standard 72-pin SIMMs. A quick physical test proved this assumption very wrong. This was a proprietary motherboard and the slots were narrower than 72-pin SIMMs and wider than 30-pin! I'd never actually seen anything like this before. I then researched and realised that this board needed 68-pin SIMMs.

eBay came to the rescue and two 4MB SIMMs arrived from Denmark! Seems they're mainly used in Roland hardware or Macintoshes. Anyway, from the photo above you would easily mistake them for 72-pin SIMMs. It all becomes obviously when you line up all the types...

Above we have a 128-pin SIMM, a 72-pin SIMM, two 68-pin SIMMs and then a 30pin SIMM. I think quickly tested in the motherboard and success! They fit!

Of course, the machine still didn't boot... time for more mucking around... (and no, it wasn't the fault of that loose screw...)

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?!