VOGONS


First post, by Silent Loon

User metadata
Rank Member
Rank
Member

Okay, my first own computer was no IBM XT, it was a Siemens AT, model name "PCD-2L" with a 286 12Mhz cpu, 4MB RAM and a 20MB MFM harddisk inside, and it looked - or looks like this:

2b493015837107.gif

This model wasn't really for the consumer market, it was targeted on small offices or companies that liked to have some kind of "slim line" PC I think.

Some month ago I wanted to revive it - but only partly succeeded: The cmos battery was - after nearly 20 years - finished. So I had to type the bios parameters of the machine every time I started it - annoying! Of course I thought about changing the battery, but I discovered that it was somehow soldered on the board, and I'm not very good in soldering. Inside the machine it looked like that:

8f88c715839087.gif

What you see is the mainboard of the PC, it's a full size "Slot-Cpu-Board" or Single Board Computer (SBC) that uses a passive 4-Slot ISA backplane. This is an industrial standard still today, but siemens abandoned this path some time afterwards, at least for their consumer products.
I put the floppy cable off, so the battery is visible. The two other cables go from the hard disk to the mfm hd-controler, which was at that time not part of the mainboard.
Note that the board is equipped with an AMD cpu!

Well, I forgot about reviving the machine, until I stumbled over an auction where "old 386 and 486 siemens industrial cpu boards" where sold. I got them for arround 7€!
I wonder if they would fit - and if it would work after all.
It works! The boards even have new batteries - it seems as if they where stored in reserve and never used!
So I pumped up my ol' 286 to a 386DX33:

a8965d15841453.gif

As you can see, this board has allready an IDE controller - and as the MFM hd is very loud, I took a CF-card (256MB, with IDE adapter) instead as hard disk (below the cables).
Note that the PSU (Made in Italy!) and the system fan are separated - which made it easy to change the old PAPST "vapor cleaner" against an Artic Cooling AF8025L (same air flow but almost quiet). So the system is now nearly noiseless.
I didn't stop there - here you can see the PCD with a HX board (I bought separately) and a Pentium 75 Mhz:

03afb415842529.gif

But is combination was allready too fast for some purposes so I finally voted for the 486DX33 board:

1537ae15842794.gif

My old PCD-2L was deaf and dumb - there was no soundcard inside. And just a 256k VGA card... So here's what I put in:
- A Diamond Speedstar Pro ISA SVGA card with 1MB and Cirrus Logic chipset (best image quality of all ISA VGA cards that I have, faster than Tseng 4000ax)
- A Turtle Beach Tropez Classic Wavetable soundcard, that is SBpro compatible, has a true Yamaha OPL3 (YMF 262) and a Wavefront synthesizer that provides General Midi (and with a special soundfont even some kind of MT-32-) compability.
- A Gravis Ultrasound Classic Rev. 2.2 with 1MB sample RAM:

cb235215843244.gif

The big advantage is that you can change the system configuration and thereby the hardware speed within minutes. Here are the boards not in - but "ready to use":

58e8f915844362.gif

From left to right:
the original 286 board; a 386-20 board with a "ad-on" Tseng 4000 graphics card that sits on the board (Does anyone know the pinouts?), a 386-25 board, the 386DX33 board and finally the Pentium 75 with passive heatsink.

Reply 1 of 6, by 5u3

User metadata
Rank Oldbie
Rank
Oldbie

Sweet! 😁

I like the concept of using a passive ISA plane and switching the CPU board when needed. This seems to be the ideal solution for retro gamers without much space for their machines. Nice work!

Silent Loon wrote:

Of course I thought about changing the battery, but I discovered that it was somehow soldered on the board, and I'm not very good in soldering.

On the photo it looks very easily replaceable, just two zip-ties and a common two-pin plug to remove.

Silent Loon wrote:

a 386-20 board with a "ad-on" Tseng 4000 graphics card that sits on the board (Does anyone know the pinouts?)

Maybe if you post a high-resolution photo of the card...

Reply 3 of 6, by Silent Loon

User metadata
Rank Member
Rank
Member
5u3 wrote:

On the photo it looks very easily replaceable, just two zip-ties and a common two-pin plug to remove.

It's wrapped in some kind of transparent plastic protection that also fixes the small +/- cables that go to the plug. I couldn't find any new battery with this. So I guess I would have to solder the cables to fix them. But you're right it's not that difficult...

5u3 wrote:

Maybe if you post a high-resolution photo of the card...

Here we are:

44010d15902161.gif

The white connectors on the top got to the mobo. At the bottom there are two possibilities to connect cables; I would guess that the 16pin-male-connector on the right (14 pins connected) is for some kind of VGA-D-sub cable. From the front it looks like that:

x + + + + + + +
+ + + + + x + + (x = not connected)

Part number is C26361-D544-W100. It's Made in USA - so maybe it's not exclusively produced for siemens and also used in other pcs?
Anyway I could not find a documentation with the pinout.

Reply 4 of 6, by keropi

User metadata
Rank l33t++
Rank
l33t++

that connector is in reality an ISA slot, very common in industrial pc's ... building an adapter would take much time, maybe search eBay for another vga of the same kind, but it won't be easy...

cT89QGt.gif Amstrad PC7486SLC-33 wanted , click me for AmiBay ad!

Reply 5 of 6, by 5u3

User metadata
Rank Oldbie
Rank
Oldbie
Silent Loon wrote:

At the bottom there are two possibilities to connect cables; I would guess that the 16pin-male-connector on the right (14 pins connected) is for some kind of VGA-D-sub cable. From the front it looks like that:

x + + + + + + +
+ + + + + x + + (x = not connected)

I think you're right, because the edge connector in the middle looks like a 26-pin VESA feature connector, which only leaves the 16(14)-pin connector for VGA output. I've never seen one like this.

It would probably be nice to use this ET4000 addon card to free another ISA slot on the backplane.
The funny thing is that the classic GUS cards also have those ISA "loop through" pins near the ISA slot connector (originally used for their 16-bit recording add-on card), but unfortunately the pin rows are differently located, so the ET4000 add-on doesn't fit.

Reply 6 of 6, by kixs

User metadata
Rank l33t
Rank
l33t

I need help wih configuring Siemens PCD-2. Its a Am286-12MHz with 4x256kb simms. Motherboard version: W26361-D458-Z4-06-05. It looks almost the same as the one in this thread.

I would like to expand memory with 2x1MB or more but then it recognizes only 512KB!? There are some dip switches but I can't figure them out.

Edit:
In the mean time I played with the dip switches and managed to get 4MB of memory recognised (EN0, EN1, EN2 switches control the amount of memory - play around with it).