Zenith Supersport 8088 (again) - "fake hdd" terminal on hdd connector

HI all,

again with the Zenith Supersport...

Thanks to you, I successfully replaced the dead FDD with a modded Samsung FDD. I also discovered the Supersport configured for 1 HDD + 1 FDD came without the 2nd floppy connector; but the mainboard has the holes for it, so I added an FDD connector another Samsung FDD (that I configured as DS0 too, so I had to use a twist cable) and -ta-dah!- now I have a 2 FDD Supersport.

The only problem is that the boot starts invoking the HDD drive, returning an error. I can hit ESC and it will continue, but I wish to remove this message.

Digging on the web, I found a clip about this computer, 2 x FDD model, showing the mainboard. Even if the quality of the image is rather bad, I can see there is some kind of terminal put into the FDD-like connector where the hdd controller is plugged, if you have the 1 hdd + 1 fdd model.

I suppose this is a terminal with some pin grounded that's preventing the machine to see there's no HDD. I don't know the right english term for that, but it's kind of a "fake hdd"... more or less...

Does anybody know how to make one of them?

BTW for some reasons, today I can't upload an image of the mainboard here... I will try to add it in a further post...

this is the connector for the HDD controller. There's something plugged in it...




just as reference: this is the HDD controller:



and this is the HDD (XT-IDE - 8 bit data)

Look for a block of DIP switches on the board. Some models used DIP switches to designate which drives were installed. I can't remember if the settings were silk screened on the board.

I already tried most dip switches configurations; actually I'm using the same config of the guy in the video from where I've taken the picture.
(https://www.youtube.com/watch?v=IvYN7xcBhHU)

It seems the HDD model is forced in some way to search the HDD in the boot sequence. So, there's a plug inside the hdd connector, jumpering some contacts in some way, or there's a difference between the hdd model bios vs. 2 fdds model bios.
Unfortunately I haven't the 2 FDDs model bios image... I only have what I've dumped from my EPROMs, that's the HDD model bios. So I can't say if there are some differences in the bios or not.

Give me a day or two to disassemble my Supersport 8088. I'm not sure if it's a HDD model, however, since it came with the left bay empty. No idea if there once sat a floppy drive or a hard drive in there. But I partly opened it once and don't remember seeing a hard disk controller card, so it's most likely no HDD version.

Timo W. said:

Give me a day or two to disassemble my Supersport 8088. I'm not sure if it's a HDD model, however, since it came with the left bay empty. No idea if there once sat a floppy drive or a hard drive in there. But I partly opened it once and don't remember seeing a hard disk controller card, so it's most likely no HDD version.

Click to expand...

ok, thank you. If the left bay is empty and you have a cover on the left side, probably it is (was) an HDD model. In this case, if you want to add a 2nd drive, you should need to solder a second FDD connector below the one already mounted. You will probably see there are the holes on the board. I did it in mine, set up the jumpers and it worked like a charm. You will probably need a proper FDD. I used a Samsung FDD drive, like Chuck explained me in this thread: http://www.vintage-computer.com/vcf...0-transform-a-1-44-MB-drive-into-a-720-KB-one, but I suppose there are other brand/model FDDs that will be suitable for that kind of mod; and the 2nd drive must to be set as DS1 (or you will need to use a twist cable, as I did).

If you have 2 FDD connectors, then probably it was a 2 FDD model. In this case, would be great if you can also dump the eprom content. If there's no terminal into the HDD slot (it is the one below the keyboard connector, on right of the the modem slot) then probably the only difference is in the BIOS. I planned to post a page on the web explaining the differences between the two models (I'm sure the SupersPORT HDDs will all die in a not so far future) and how to convert an HDD model into a 2 FDD one. I also already downloaded the content of my EPROMs and if you can do the same, I will put both for download on the web page.

If the left bay is empty and you have a cover on the left side, probably it is (was) an HDD model.

Click to expand...

The cover on the left is missing, so it's most likely a non-HDD model and there was a floppy drive installed. I should add that it's not working at the moment, but I hope to get it repaired sometime.

Timo W. said:

The cover on the left is missing, so it's most likely a non-HDD model and there was a floppy drive installed. I should add that it's not working at the moment, but I hope to get it repaired sometime.

Click to expand...

These are good news... it means probably you have the 2 FDD EPROMs installed. Have you an EPROM burner for to download the two EPROMs content?

What is the problem with it? Does it refuses to fire up (dead) or it lights on but it doesn't boot? I noticed if you plug the FDD in the wrong slot, it doesn't fire up and seems a dead PC. So, if somebody removed one FDD and for some reason plug the remaining one in the wrong connector, it won't start until you remove the flat cable.

One more request: if/when you will open your Supersport, would you take some good pictures of the mainboard, *both* sides? I was talking with a friend about the chance of an undocumented jumper on the 2 FDD model put to avoid people upgrading the laptop in the HDD model on their own. Maybe an SMD jumper or something similar. In the 1980s, without internet, was quite difficult to obtain infos about that, so in that era this kind of business move would pay...

It currently doesn't do anything beside turning on the lcd backlight. I've got a second one (Supersport 80286) which is almost working, only the hdd is toast. I guess I can take the floppy drive from that one to fix the 8088.

Sure I can take photos of the mainboard. I always do that anyway.

Timo W. said:

It currently doesn't do anything beside turning on the lcd backlight.

Click to expand...

I think it's a good sign; mine also did it because of boot problem. Maybe it doesn't recognize a drive and get stucked. See if there and HDC plugged in the mainboard behind the keyboard. This would say it's an HDD model without HDD, just the HDC.

Timo W. said:

I've got a second one (Supersport 80286) which is almost working, only the hdd is toast. I guess I can take the floppy drive from that one to fix the 8088.

Click to expand...

Ok. Really, you only need any FDD with DC/RY and DS0/1 jumpers. Chuck(G) gave me a good advice about that, as I mentioned in a previous post.

Timo W. said:

Sure I can take photos of the mainboard. I always do that anyway.

Click to expand...

Great. This will help us to see if there are any differences. Can you also download the EPROMs content?

I just opened the Supersport and it's indeed a non-HDD model. There are two floppy drive cables and no HDD controller. I'll post more details in a few minutes.

Here's a first picture. Nothing plugged into the HDD connector.

Great, it means the difference is in the bios and/or in some jumpers on the board.

Please, can you provide some high res pictures of the whole board, both sides?

More: can you download the BIOS from the two EPROMs?

I only have a ROM on 10D; 11D is empty. If you have two ROMs, maybe 11D is the HDD BIOS extension?

Should I get the system running again, I can dump the BIOS. I have no other way currently to dump ROMs.

High-res pictures of the mainboard will follow.

Timo W. said:

I only have a ROM on 10D; 11D is empty. If you have two ROMs, maybe 11D is the HDD BIOS extension?

Click to expand...

maybe. 10D is 256 kb while 11D is 64kb. What is the label code of 10D eprom?

Timo W. said:

Should I get the system running again, I can dump the BIOS. I have no other way currently to dump ROMs.

Click to expand...

ok. ctrl+alt+ins (or ctrl+alt+break) should open the bios menu. if nothing happens, try to remove everything connected to the mainboard and see if you get some msgs.

Timo W. said:

High-res pictures of the mainboard will follow.

Click to expand...

ok thank you

The label of 10D reads:

Z184M
V3.1D

Mine is: MB01B V 3.1
But this probably is not the difference, really. I've seen two clips on you tube: http://www.youtube.com/watch?v=wwaul3hpO3I (part 1) and http://www.youtube.com/watch?v=LF2V53cPt3A (part 2) showing an HDD model like mine, with bios like yours.

I will try to open mine again and to remove the 11D eprom, to see if it will transform it like a 2 FDD model.

Of course, a comparison between my mainboard and yours by the pictures will solve any doubts.

Simply removing the 11D eprom doesn't solve (as I suspected): it doesn't boot without the two eprom. There should be some undocumented jumper... maybe.

Close to the 10D eprom there are two (missing) jumpers, JP1 for 278H - 378H switch (factory set at 378H) and JP2 for 256 - 512 (factory set at 256, I suppose it is referred to the 10D eprom size). There's a missing JP3 in the upper right corner (component side, leaving the cpu at left) too, not to mention some missing capacitors, both sides.

Definitely, some high res pictures of your board, both sides, would help a lot. If you can't post here high res pictures, I can send you my email by PM.

For future references, I attach here a zip file with the eprom images View attachment Zenith SUPERSPORT 8088 (internal hard disk) EPROMs image.zip