8088 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

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8088 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

Postby AppleDash » 2018-5-27 @ 04:28

I've had a bunch of 8088 system parts in my collection for awhile, dismantled from various untested systems or otherwise acquired in uncertain condition. Today, I decided to try and make a working system out of them, mainly because I want a system that uses CGA instead of VGA.

The components I am using are an unknown board, an unknown I/O card, and a "Better Products Colorcard" CGA card. Pictures are here (links as they are huge when used with img tags):

Board:

https://appledash.org/img/8086/8086_board.jpg

I/O card:

https://appledash.org/img/8086/io_card.jpg

Colorcard:

https://appledash.org/img/8086/colorcard_front.jpg
https://appledash.org/img/8086/colorcard_back.jpg

All I have connected are the PSU, the expansion cards, and the monitor to the CGA card. No drives yet.

As stated, when I power on the system, all I get is a blinking cursor in the upper left corner of the monitor. Any ideas what I'm doing wrong? And... if anyone could help me identify the unknown parts, that would be great!
Last edited by AppleDash on 2018-5-27 @ 08:22, edited 1 time in total.
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Re: 8086 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

Postby matze79 » 2018-5-27 @ 06:04

did you reseat and clean all socketed ic's ?
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Re: 8086 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

Postby ReL » 2018-5-27 @ 07:24

xt computer here the motherboard manual
http://arvutimuuseum.ee/th99/m/U-Z/31541.htm

I have one same
https://imgur.com/qIFPPsW
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Re: 8086 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

Postby Anonymous Coward » 2018-5-27 @ 08:01

Although the picture is blurry, I am guessing it should be an 8088 board, as an 8086 would normally have a BIOS spread across two ROMs.
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Re: 8086 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

Postby AppleDash » 2018-5-27 @ 08:23

matze79 wrote:did you reseat and clean all socketed ic's ?


I have not, but I will do now.

ReL wrote:xt computer here the motherboard manual
http://arvutimuuseum.ee/th99/m/U-Z/31541.htm

I have one same
https://imgur.com/qIFPPsW


Awesome, thanks.

Anonymous Coward wrote:Although the picture is blurry, I am guessing it should be an 8088 board, as an 8086 would normally have a BIOS spread across two ROMs.


Looks like you're correct!
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Re: 8088 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

Postby derSammler » 2018-5-27 @ 09:01

AppleDash wrote:As stated, when I power on the system, all I get is a blinking cursor in the upper left corner of the monitor. Any ideas what I'm doing wrong? And... if anyone could help me identify the unknown parts, that would be great!

You probably did nothing wrong apart from not showing enough patience. The XT just shows a blinking cursor when turned on while testing memory. With a full 640k, this can take up to 90 seconds.
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Re: 8088 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

Postby AppleDash » 2018-5-27 @ 09:33

derSammler wrote:
AppleDash wrote:As stated, when I power on the system, all I get is a blinking cursor in the upper left corner of the monitor. Any ideas what I'm doing wrong? And... if anyone could help me identify the unknown parts, that would be great!

You probably did nothing wrong apart from not showing enough patience. The XT just shows a blinking cursor when turned on while testing memory. With a full 640k, this can take up to 90 seconds.


I just powered it on again and waited a full 3 minutes on the clock... And nothing.

Since I have realized this is an XT and not an AT, could the problem have anything to do with my keyboard? I am using an AT keyboard, though I do own an XT keyboard.
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Re: 8088 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

Postby Scali » 2018-5-27 @ 10:17

derSammler wrote:
AppleDash wrote:As stated, when I power on the system, all I get is a blinking cursor in the upper left corner of the monitor. Any ideas what I'm doing wrong? And... if anyone could help me identify the unknown parts, that would be great!

You probably did nothing wrong apart from not showing enough patience. The XT just shows a blinking cursor when turned on while testing memory. With a full 640k, this can take up to 90 seconds.


Another explanation could be that it is not configured correctly.
XTs generally have jumpers or dip switches on the motherboard to select between mono and color display adapters. In this case, probably the blue block of switches (that is the same as on a real IBM XT, so chances are they also work the same, so if you can't find docs for your specific board, try this: http://minuszerodegrees.net/5160/misc/5 ... ttings.htm, switches 5 and 6. In your picture they are both on, so it expects a VGA card or such, try 5 on and 6 off)
If it is jumpered to mono, then the BIOS will send all text and video commands to an MDA/Hercules-compatible card. The CGA card will work, and boot up in textmode, but all you'll see is a cursor, because it never receives any other data or commands.

If this is the case, the machine should actually be able to boot, so you could try to boot from a DOS floppy, and then you can type 'mode co80' to switch to CGA.
Last edited by Scali on 2018-5-27 @ 10:38, edited 3 times in total.
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Re: 8088 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

Postby derSammler » 2018-5-27 @ 10:21

Wait, you have that i/o card installed but no drives. It may wait for the drives to be ready, which never happens.

Remove everything except the CGA card and power it on again. Also remove the keyboard, as an AT one will not work anyway. You should get an 301 error after the memory has been tested. Then, add the expansion cards one by one until you find the one that causes the system to hang. Do not install the i/o card with no drives attached, unless you know how to set the dip switches for that case.
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Re: 8088 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

Postby Scali » 2018-5-27 @ 12:10

I'd check the dipswitches first (see my post above). Pretty sure that's it.
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Re: 8088 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

Postby AppleDash » 2018-5-27 @ 19:17

Scali wrote:Another explanation could be that it is not configured correctly.
XTs generally have jumpers or dip switches on the motherboard to select between mono and color display adapters. In this case, probably the blue block of switches (that is the same as on a real IBM XT, so chances are they also work the same, so if you can't find docs for your specific board, try this: http://minuszerodegrees.net/5160/misc/5 ... ttings.htm, switches 5 and 6. In your picture they are both on, so it expects a VGA card or such, try 5 on and 6 off)
If it is jumpered to mono, then the BIOS will send all text and video commands to an MDA/Hercules-compatible card. The CGA card will work, and boot up in textmode, but all you'll see is a cursor, because it never receives any other data or commands.

If this is the case, the machine should actually be able to boot, so you could try to boot from a DOS floppy, and then you can type 'mode co80' to switch to CGA.


Looks like we have a winner! I set the switches to 5 on, 6 off, and immediately got the BIOS POST screen and memory-testing information. Thanks a lot! I'll try and get it running from here, and update this thread with the outcome.
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Re: 8088 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

Postby Moogle! » 2018-5-27 @ 19:33

Incidentally, are you sure that is a CGA card and not an EGA card? I don't think I have ever seen a CGA with the two RCA jacks on it. I believe monochrome and EGA use the same dip setting, but I could be wrong.

Also, is that not the same XT board Red Hill talks about?

EDIT: Nope, Google says CGA.
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Re: 8088 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

Postby AppleDash » 2018-5-27 @ 20:05

Moogle! wrote:Incidentally, are you sure that is a CGA card and not an EGA card? I don't think I have ever seen a CGA with the two RCA jacks on it. I believe monochrome and EGA use the same dip setting, but I could be wrong.

Also, is that not the same XT board Red Hill talks about?

EDIT: Nope, Google says CGA.


I want to know what you Googled, because I've never been able to find anything about this card anywhere.

Also, could be, but so many of them look exactly the same while being from entirely different manufacturers and having subtle differences.
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Re: 8088 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

Postby Moogle! » 2018-5-27 @ 20:35

http://www.vgamuseum.info/index.php/com ... mc-um6845r

Now, as I said, it has two RCA jacks, which I found odd, and does suggest EGA, but it doesn't appear to have it's own BIOS, which suggest CGA. The link above suggest CGA, and I have seen CGA cards from that late in the eghties.
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Re: 8088 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

Postby PTherapist » 2018-5-27 @ 22:23

I have a very similar looking CGA graphics card that I bought fairly recently and have been playing around with also in an XT build, excuse the picture quality I must take a better pic at some point:

https://i.imgur.com/sXx596C.jpg

I also struggled to find any info out about this card too.

The top RCA output is Monochrome, whilst the bottom provides Colour.

My experience using it thus far, on composite only: when set to 80 column color mode some programs will display as just black & white stripes on the bottom RCA, rendering the text unreadable (eg. IBM E Editor & XTree Gold among others). But switching over to the top RCA gives a nice 80 column greyscale with readable text. Saves having to resort to either switching to 40 column mode or forcing Black & White via MODE BW80.
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Re: 8088 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

Postby Moogle! » 2018-5-28 @ 05:21

You know, I wonder if it actually an S-Video (Y/C) signal, like the C64 used. That would explain why the black and white jack (luma) worked alright, but the color (chroma) jack was all weird.
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Re: 8088 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

Postby Tiido » 2018-5-28 @ 05:55

Chroma shouldn't really be able to show anything unless it has huge amount of leakage from luma, there's no sync info on the chroma line.
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Re: 8088 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

Postby AppleDash » 2018-6-02 @ 07:14

Exciting little update... When I have the HDD controller (IBM 1816101) and HDD (ST-412, tested good in another system) present, I get a 1701 error and then the system hangs. When I remove the HDD controller and leave just the floppy controller, it gives me the standard expected "Insert a disk in drive A:" error. Any ideas?
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Re: 8088 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

Postby PTherapist » 2018-6-02 @ 07:37

1701 is a HDD controller error, as per the info on this link:

http://minuszerodegrees.net/5150_5160/h ... lities.htm

You say you tested that HDD on another system, was it tested with the same HDD controller? If not, it's possible that the controller doesn't like the ST-412 or something else as suggested in that link is wrong.
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Re: 8088 from a bunch of random parts - nothing but a blinking cursor. What's wrong?

Postby AppleDash » 2018-6-02 @ 07:52

PTherapist wrote:1701 is a HDD controller error, as per the info on this link:

http://minuszerodegrees.net/5150_5160/h ... lities.htm

You say you tested that HDD on another system, was it tested with the same HDD controller? If not, it's possible that the controller doesn't like the ST-412 or something else as suggested in that link is wrong.


I think the error is simply because the drive was not low-level formatted on the controller that I am using in the XT. In order to do so, however, I need to boot to DOS and run DEBUG... But if the system hangs no matter what with the controller present, I can't do that.

Edit: Also, the controller *only* supports the ST-412.
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