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View Full Version : I'd like help in identifying an IBM XT clone



sanchezman
June 15th, 2014, 10:51 AM
Earlier today I picked up this IBM clone (http://imgur.com/a/N9Jlw) at a swap meet for $2. The case says "Avantage XT turbo", but I cannot find any information about it online. I opened it up, and looking at the components' patent years, I can only say that it is from 1987 or later. I've also noticed that although it says XT, it seems as if the HDD has been removed. The previous owner was also kind enough to leave a DOS backup disk in one of the drives, but I have no clue if it is damaged or not. While I own a few other vintage computers, this is the first IBM/IBM compatible that I've had, so I'd like to learn a bit more about it.

On another note, I'd love to use it, but I don't have a monitor. I know it outputs cga, but I don't have any cga monitors. Would any of these (http://www.ebay.com/sch/i.html?_odkw=ega+monitor&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR3.TRC2.A0.H0.Xcga+to +vga&_nkw=cga+to+vga&_sacat=0) work to plug this computer into, say, a modern HDTV with a vga port on the side? I'd also like some help with the POST beeps that the computer makes. I know that the beeps tell what tests the computer passes, but if I'm not mistaken, beeps codes are different for each clone BIOS. Since I don't know anything about this computer, I couldn't look up the codes. Anyway, here's a link (http://youtu.be/A-vE1mvQ4cE) to the startup beeps it makes.

Thanks in advance for any and all help

SpidersWeb
June 15th, 2014, 11:49 AM
It's probably going "301 Keyboard Error" ;) Looks like you got a good one there.

Every man and his dog was selling XT clones under various brands - there were a few big brands but I think you have a generic one there. The key will be identifying the internals like the motherboard etc. The last two I got were "Exzel" and "Concept" but both were actually DTK on the inside (cards, motherboard etc). You'd just buy the parts, build it, and sell it under your brand name.

For the CGA, does it have composite out? It's not ideal (poor appearance) but you should get output on your TV. I can't comment on those CGA converters as I haven't used one, but I'd make sure it does IBM PC CGA - apparently it's a little different to the style commonly used in the arcade.

Also just so you're aware - you will need an XT class keyboard to go with this, a normal AT style keyboard will not work.

SomeGuy
June 15th, 2014, 12:00 PM
That is any one of a bazillion different XT clones put together from generic inexpensive Taiwanese parts. In the late 80s everyone and their mother was throwing these things together from generic parts and slapping their own label on it.

In this case, what you need to do is pull out the cards and motherboard and post clear pictures of each for individual identification.

From a distance, they look like DTK (Taiwanese) parts. Are you sure that video card is CGA? I don't see a composite output. It looks more like MDA. If it is CGA, it might have a composite output on one of the plug pins or on an internal header that you can connect to a TV. The "CGA" adapters out there are a slightly different "CGA" (not IBM CGA) and apparently need an additional adapter for correct color. If that is MDA, there is not much you can use that with.

Your best is probably to just throw in an 8-bit compatible VGA card. Once you can get video, the BIOS splash screen might tell you a tad more about the motherboard.

BTW, it is possible it may have been sold without a hard drive, although that would have been a bit odd. "XT" on these only describes the level of compatiblity, meaning an 8-bit ISA expansion, and 8088 or V20 CPU.

Do you have any idea about where this machine might have been sold originally? That could lead to more information about whoever "Advantage" was.

Personally, I am a fan of these things because there was so much variety and customizeability.

SpidersWeb
June 15th, 2014, 12:07 PM
hah I missed the photo link.

As SomeGuy mentioned, it's possible it never had a hard drive. I'd agree with this because if someone had pulled the hard drive, it's unlikely they would've replaced it with the original blanking plates (rear and front) and screw - usually people just tear stuff out - and the power connectors look unused, not like they sat bent at a weird angle for years on end.

I'd also agree that card is more likely MDA - usually cards were either CGA *or* MDA+PARALLEL. Besides looking at the card, check the switches on the motherboard, if it was configured for mono then switches 5 6 will both be OFF.

Edit: didn't recognise the motherboard layout, but I recognise that logo, 99% sure it's a DTK model.
Edit2: http://stason.org/TULARC/pc/motherboards/D/DTK-COMPUTER-INC-8088-PIM-TB08-Z.html#.U54BZShj9aQ (also available in 10Mhz) <-- educated guess, not confirmed

sanchezman
June 15th, 2014, 01:36 PM
Edit2: http://stason.org/TULARC/pc/motherbo...l#.U54BZShj9aQ (also available in 10Mhz) <-- educated guess, not confirmed

I think you're right. That diagram looks like what I have.

It looks like this is indeed an MDA + Parallel output for video. Does this mean that I can replace it with any 8-bit ISA video card? In the motherboard link that SpidersWeb provided, the documentation only talks about setting switches 5&6 in various positions to select between CGA, MDA, or EGA. Is it not possible to choose VGA? What if I got a combination VGA, EGA card? How would I select the video mode then?


Also just so you're aware - you will need an XT class keyboard to go with this, a normal AT style keyboard will not work.
Would a PS/2 keyboard and this adapter (http://www.ebay.com/itm/6-inch-PS-2-to-AT-Keyboard-Adapter-/141314590723?pt=US_Parallel_Serial_PS_2_Cables_Ada pters&hash=item20e7018803) work, or do I have to specifically get something that says XT, like this (http://www.ebay.com/itm/MOTOROLA-KT-32903-01-CONNECTOR-KIT-PS-2-TO-AT-XT-NEW-IN-PACKAGE-/390423726987?pt=LH_DefaultDomain_0&hash=item5ae7114b8b)?

george
June 15th, 2014, 01:49 PM
These cables won't work.The protocol of XT keyboards is different therefore you need an XT compatible keyboard. You could use whatever 8-bit ISA video card you like. Even some 16-bit VGA cards work in XT machines.

SpidersWeb
June 15th, 2014, 02:00 PM
Those adaptors wont work because the issue isn't the plug, it's the fact it's a different interface - so the keyboard must actually support the XT standard which was dropped a very long time ago now. You'll need either an XT keyboard, or one with an XT / AT switch underneath, or one that auto-switches (hard to tell for certain).

There was an AT to XT project on here, I'll see if I can find it, it was a circuit board that translated the signals. (Edit: AT2XTKBD http://n8vem-sbc.pbworks.com/w/browse/#view=ViewFolder&param=MINI%20AT2XTKBD )

VGA will be ON ON for switches 5 & 6 - it equates to none, because the card sets itself up with a Video ROM. I have a DTK TURBO 640 which is older, and that starts up VGA no problem, so I would expect your board to do so as well.

However, most VGA cards do not support the 8088 CPU - they will hang. So you'll either need a V20 CPU, or a card that is certainly 8088 friendly (hard to tell without trying).

If you have 8 or 16 bit ISA VGA cards lying around, it certainly can't hurt to try them out. 16 bit cards often work in 8 bit slots, it's just the CPU limitation that can be a nuisance.

Welcome to the wonderful world of the XT!

SomeGuy
June 15th, 2014, 02:00 PM
For the dip switches, you normally set them to EGA or NONE. The on board BIOS normally only needs to know about MDA or CGA because in those cases it must initialize the cards itself. In the case of EGA/VGA, the cards provide their own BIOS.

Malc
June 15th, 2014, 02:10 PM
Looks like A nice clean looking machine and a bargain at $2, I do like the look of some of those old clones :-)

Stone
June 15th, 2014, 02:29 PM
However, most VGA cards do not support the 8088 CPU - they will hang. So you'll either need a V20 CPU, or a card that is certainly 8088 friendly (hard to tell without trying).

If you have 8 or 16 bit ISA VGA cards lying around, it certainly can't hurt to try them out. 16 bit cards often work in 8 bit slots, it's just the CPU limitation that can be a nuisance.I have a couple of 16-bit VGA cards that work fine on my 8088 XT. One is a Trident and the other is an Octek with a Chips & Technologies chipset.

sanchezman
June 15th, 2014, 03:03 PM
I found the motherboard's model number. Looks like it's this one: http://stason.org/TULARC/pc/motherboards/D/DTK-COMPUTER-INC-8088-PIM-TB10-Z.html#.U54kGrEt3nc

SpidersWeb
June 15th, 2014, 03:07 PM
Yeah that's the 10Mhz version :) Should fly pretty nicely! That one actually shows ON ON as being for EGA/VGA.
Is the CPU a V20 or 8088?

sanchezman
June 15th, 2014, 03:25 PM
I believe it's the V-20. Photo of it here (http://imgur.com/E2fLtNB)

Another question: What's the difference between a 16bit and an 8bit video card? Is it related to the number of colors it can represent, or the size of a data bus on it, or something else? What determines whether or not it will work in a given IBM?

sanchezman
June 15th, 2014, 04:29 PM
Here's the best photo I could take of the CPU (http://i.imgur.com/E2fLtNB.jpg). The part that might say V-20 is hidden under one of the floppy drives, but I'm assuming that because it says NEC, it is a V-20.

I also had another question about ISA cards. What is the differentiation between 8 and 16 bit card? What determines when or where an 8 or 16 bit card can/should be used?

Chuck(G)
June 15th, 2014, 04:36 PM
Here's the best photo I could take of the CPU (http://i.imgur.com/E2fLtNB.jpg). The part that might say V-20 is hidden under one of the floppy drives, but I'm assuming that because it says NEC, it is a V-20.

NEC, believe it or not, also manufactured 8088s:

http://cdn.cpu-world.com/CPUs/8088/S_NEC-D8088D-2.jpg

SpidersWeb
June 15th, 2014, 04:41 PM
Do you have any VGA cards to throw in and see what happens?

SpidersWeb
June 15th, 2014, 05:04 PM
I also had another question about ISA cards. What is the differentiation between 8 and 16 bit card? What determines when or where an 8 or 16 bit card can/should be used?
I'm not an expert on ISA, but generally it depends on if it needs 16 bit transfers, high DMA, and/or high IRQ. Sadly this includes the normal IDE we know and love - but there is the XTIDE and XT-CF projects out now.

Most VGA cards I've owned have had an option (usually auto detect) for an 8 bit slot, but still many figured it would be an 8 bit slot in a 286 or 386. I've got one Trident with 8bit mode jumpers on it - still wont work with an 8088 but fine with a V20. Easy for me to find one that does work because I have a bunch to play with, but if you were ordering one especially off ebay it could be a pain.

sanchezman
June 16th, 2014, 07:01 AM
Unfortunately, I don't have any video cards around, VGA or otherwise.

I also took a look at the computer more carefully, and it seems to be laid out differently than what this diagram (http://stason.org/TULARC/pc/motherboards/D/DTK-COMPUTER-INC-8088-PIM-TB10-Z.html#.U54kGrEt3nc) led me to believe. Here's a diagram I drew up of what it looks like:
http://i.imgur.com/jVlnXGT.png

If that Siemen's Sa 8088 above the empty 8087 slot is the processor, then it seems like it's in the wrong place.

sergey
June 16th, 2014, 07:35 AM
Here's the best photo I could take of the CPU (http://i.imgur.com/E2fLtNB.jpg). The part that might say V-20 is hidden under one of the floppy drives, but I'm assuming that because it says NEC, it is a V-20.


That is 8255 PPI chip, not a CPU... The CPU will have either 8088 or D70108 (V20) marking on it.



I also had another question about ISA cards. What is the differentiation between 8 and 16 bit card? What determines when or where an 8 or 16 bit card can/should be used?


There are many differences: 16-bit has 8 more data bits, 4 more address bits, additional DMA channels, additional IRQ channels, limited bus master support.
More interesting questions is what 16-bit cards (or cards that appear to have 16-bit connector) are compatible with 8-bit PC/XT bus and what are not. Here is an incomplete list:
- VGA - some are 8-bit compatible, some are not. Some are listed in this thread (http://www.vintage-computer.com/vcforum/showthread.php?26432-8bit-Friendly-ISA-VGA-cards). Also it was a page on the Wiki, but I can't find it now. Trident TVGA8900/TVGA9000 based cards will work in 8-bit slots, but they need to have their jumpers set correctly for 8-bit operation. Trident VGA BIOS works on 8088 just fine, at least several versions that I've tried.
- Multi-I/O cards (popular in late 80's and early 90's AT clones). Floppy disk controller, joystick, serial and parallel ports normally work on 8-bit, IDE controller don't (but I think some guys were able to use it with CF cards and XT-IDE BIOS extension). Floppy disk controller needs something like 2M to support high density (1.2MB/1.44MB disks), but 3.5"/720 KB disks should work without any additional drivers.
- Sound cards: Creative Vibra16vx, ESS688, ESS1868, AD1816, AD1819 and many more actually have 8-bit interface (16-bit part can be used for IDE, and additional interrupts). Many of these cards need a PnP enabler utility, which normally uses 186+ instructions (NEC V20 supports them). But some cards can be configured with jumpers.

SpidersWeb
June 16th, 2014, 12:12 PM
Yeah layout seems different. Nice work on the diagram, not many would go to that effort :)
See if you can see a model number - often with DTK it'll be "PIM-xxxx". But it's not too important, because they're mostly all the same anyway.

So it looks like you've got an 8088. I think your display options will be one of:

- get an MDA display (often called Hercules Monochrome, IBM 5151 is one of those)
- get a CGA card with composite out and use a TV (I'm not a fan of this)
- get a CGA card and a CGA display - bit more common - I'm using an Amiga display on one of my PCs at the moment haha
- get a VGA card that someone has tested on an 8088
- get a VGA card and maybe a V20 chip if required (if you don't mind removing and installing a new CPU)
- grab a bunch of old looking VGA cards and try your luck

** if ordering a single VGA card, try to check if it supports being in an 8 bit slot, most do but I can't guarantee they all do.
Check this page, 8 bit friendly cards (http://www.vintage-computer.com/vcforum/showthread.php?26432-8bit-Friendly-ISA-VGA-cards&p=329466) in the VCWiki

sanchezman
June 16th, 2014, 02:45 PM
Yeah layout seems different.
But that's what seems so strange. The model number on the board says DTK PIM-TB10-Z, the same as in the diagram I linked to earlier, but my board seems to be different. I'm guess I'm just a bit surprised that my board has the same model number, yet a different layout. Did DTK produce variations of identical model numbers?

Regarding video cards, I think I'll just pick up a CGA with composite out for convenience's sake. I'll then keep an eye out for cards and monitors at local swap meets, and take it from there.

Stone
June 16th, 2014, 02:57 PM
Regarding video cards, I think I'll just pick up a CGA with composite out for convenience's sake. I'll then keep an eye out for cards and monitors at local swap meets, and take it from there.I've got one if you're interested. PM for details.

SpidersWeb
June 16th, 2014, 02:58 PM
It might just be an error in TULARC, or a different revision of the board. Most of my parts have matched TULARC pretty well - the worst I've had would be labeling or a single jumper moved, different layout is a bit unusual.

CGA card with composite sounds like a good plan. You get to see what it's spewing out for now, and can throw on a color monitor later.
You'll still need to grab a keyboard at some point - hopefully one turns up at a reasonable price.

modem7
June 17th, 2014, 12:03 AM
But that's what seems so strange. The model number on the board says DTK PIM-TB10-Z, the same as in the diagram I linked to earlier, but my board seems to be different. I'm guess I'm just a bit surprised that my board has the same model number, yet a different layout.
Does your motherboard match the diagram on the final page of the PIM-TB10 manual at [here (http://www.minuszerodegrees.net/manuals/10%20Mhz%20PIM-TB10%20Turbo%20Mainboard.pdf)] ?

modem7
June 17th, 2014, 12:50 AM
There was an AT keyboard to XT project on here, I'll see if I can find it, it was a circuit board that translated the signals. (Edit: AT2XTKBD http://n8vem-sbc.pbworks.com/w/browse/#view=ViewFolderÂm=MINI%20AT2XTKBD )
Information is also [here (http://www.vintage-computer.com/vcforum/showthread.php?26426-AT2XT-keyboard-converter)].

SpidersWeb
June 17th, 2014, 01:32 AM
Information is also [here (http://www.vintage-computer.com/vcforum/showthread.php?26426-AT2XT-keyboard-converter)].

That's a much better link, thanks :)