View Full Version : Unkown 8086 clone

September 11th, 2010, 09:38 AM
Hello there!

I've got some annoying problems with my mini 8086 clone, and I was redirected here for help.

Here is some picture of the 8086: 1 (http://picasaweb.google.hu/demonbob/RetroHardware#5515666462260882498),2 (http://picasaweb.google.hu/demonbob/RetroHardware#5515665950364489266),3 (http://picasaweb.google.hu/demonbob/RetroHardware#5515665961574366034),4 (http://picasaweb.google.hu/demonbob/RetroHardware#5515665975737721474),5 (http://picasaweb.google.hu/demonbob/RetroHardware#5515665990395474818),6 (http://picasaweb.google.hu/demonbob/RetroHardware#5515666000355983250). The shape of the board is like a full length, full height isa card, and all of the extension cards are connected through a 16 bit isa riser card (but the mobo has only pins at the 8 bit part of the bus).

The first and biggest of all problems, that I want to install a SCSI card. So I did. It's an Adaptec 1542CF, with the "less jumper, more software bios" feature. The mobo mostly doesn't react to it, it's rare when I see the Adaptec's bios message at the post process. When the bios of SCSI card can successfully "interrupt" the post procedure, there is always an error about "bios initialization error" and something about shadow ram (I forgot to write down the exact message). Maybe the card wants to copy the value of the bios rom, to the same address in ram, and it's failing because this area is upper to the 640kB.

So...the mobo has only 640kB dip ram installed and there was 4 empty simm ram place, I've installed ~4mb of ram, but the mobo saw only the on-board 640kB. Changed the ram modules..maybe I've installed them incorrectly, or something else. Nothing changed with different rams. Maybe there's something to do with the jumpers on the board, but without any jumper reference I don't really want to. I've searched a lot for the jumper guide of the manual, without any luck.

That's where I'm stuck...any idea about the scsi card, memory size problem? Or do somebody recognize this board and has some jumper manual for it? ;)

Captain Midnight
September 11th, 2010, 09:57 AM
If the card is trying to copy its ROM contents or the contents of the system ROM into shadow RAM, yeah that's going to be an issue with an XT class system because to your point, it probably can't recognize the "UMB" per se. Do you have a less-friendly, more jumper less BIOS card?

The SIMM slots are definately unusual for an 8086 class machine from my experience. I seriously doubt there's anything you can do to get the system to post any more than 640K. Only thing I can think of is there might be some software drivers out there that might be able to map EMS off it. When it POSTS, does the BIOS version give you any ideas or is it a generic BIOS (i.e. Phoenix, Award, etc.)?

Anybody think of something else?

September 11th, 2010, 10:31 AM
Sadly that's the only isa scsi card I've got with bios. There is something on my mind, which I've haven't tried yet...if I'm right, the default irq of the card is 11, which is over the accessable highest 8 bit irq...which is around 9. I'm not sure about this one. But it's a 8086, with 16 bit isa ports, so it shouldn't be a problem. The confusing thing is the connector which goes into the riser card; there are no pins on the "+8" bit part.

I don't really want to map the inserted simm rams to ems. I'm not going to run any program which need more than base memory. All I want is umb to put an end to the "shadow ram error", and for that, the board needs to see the simm moduls somehow from hardware.

I've just taken a picture (http://picasaweb.google.hu/demonbob/RetroHardware#5515722463837286210)of the post screen, with an unplugged keyboard. The white bars is a flashing "keyboard error" message. There is nothing special. Some kind of Oak bios, as half of the ics at the mobo is Oak labeled. Nothing usefull information besides the cpu clock and the memory size....at least for me. :)

Anonymous Coward
September 12th, 2010, 05:59 PM
Very cool 8086. I wonder if the EMS memory has a 16-bit datapath too....

Captain Midnight
September 13th, 2010, 04:23 PM
On the 16 bit part, you may have a point. I seem to recall the AT&T PC 6300 had a similar predicament, but I didn't have a whole lot of contact with that machine, so I won't pontificate more on that.


Here's the link I found for your SCSI adapter. In section 6, it discusses executing the setup program from debug, which might give you a way to change IRQ and other I/O settings or help the card basically diagnose itself?

September 14th, 2010, 12:23 AM
In section 6, it discusses executing the setup program from debug, which might give you a way to change IRQ and other I/O settings or help the card basically diagnose itself?
I've also tried this one. Basically, executing this config program would access me to the same panel which can be access through the bios of the card. Also, it didn't worked. My guess is that the bios can't be reached from this "semi-16" bit ports, either way. Of course, I tried the card and even this util from another machine, and worked flawlessly. :(
Now I'm hunting for Future Domain cards. In another topic of this forum, lot of guy mentioned some versions of this manufacturer, working in 8 bit slots. Hopefully I will be lucky. :)

Very cool 8086.
I agree. Kind of "modern" 8086, and very small. Both of them is important to me, because I don't have too much storage space, and because it is ~ ten years younger than the oldest 8086 pcs, hopefully it will have less errors in the future. :)