AT&T 6300 - 25-pin Monitor Model?

Hello folks, I've got an AT&T 6300 WGS that I'm looking to kit out with the period AT&T-ness to go along with. Inside the machine is a VDC400 video card, which seems to be a CGA-compatible card with the 25-pin connector that mates quite nicely with my two AT&T CRT-313-B monitors. (FWIW, the two big changes I've noticed from the plain 6300 are that the WGS has done away with the proprietary 16-bit ISA (where the 62-pin and 38-pin parts are completely different connectors) in favor of strictly 8-bit ISA, and that the battery is on a totally separate board from the motherboard. This makes it more in-line with an Olivetti M240 rather than an M24.)

Only problem is, neither of my 313-Bs actually light up. Neither of them has a separate power plug, so the power must be provided through the 25-pin cable from the video card.

Here's what I've tried:

• My VDC400 is plugged into a special power rail from the PSU that provides 15V. At first, I noticed the 15V pin on the connector was open, so I replaced a pico fuse right in front of it, and now the 15V pin is back in business, but no luck with the monitors. The AT&T 6300 manual states the importance of the 15V line for running monochrome monitors.
• I have set the DIP sockets in accordance with the Olivetti M240 manual, and even tried iterating through every available video mode, but nothing helped.
• I installed a typical IBM MDA card and configured the DIP sockets accordingly (not requiring the 15V rail, of course), and saw correct system output on my IBM 5151.

Of course, it's highly likely my 313-Bs are simply dead. However, I'm wondering if the 313-B was even the logical choice to go with these systems anyway (especially the VDC400), or if that would've been a different CRT altogether. I'm aware of a few other models, namely the 313-H and -M, 314, 318, and 319 monitors. However, I know very little about their specifics, and I assume these reflect different standards and thus can (or must) be paired with different cards. Any help in this regard would be appreciated! The monitor is (AFAIK) the last piece I need, since I have a bunch of AT&T keyboards (too many, actually) and even an AT&T mouse.

Also, shameless plug for VCF Southwest - come & see me June 14-16, 2024 at UT Dallas!

mrcity said:

This makes it more in-line with an Olivetti M240 rather than an M24

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The 6300WGS is a M240.

You can plug in any other graphics card wich runs in 8 Bit ISA. One of my M240 has a Paradise VGA card what is nice. (It's a 16 Bit card but it is happy in 8 Bit Slot)

Call me weird, but I'm trying to make a matched set, even if that means I'm stuck with MDA for the moment So I saw an AT&T monitor on eBay and it came today! Now I'm in business. This is the CRT-314 monitor with 25-pin interface matching the video card. I disconnected the 15V line into the video card (just in case it would fry something in this monitor) and it doesn't seem to care.



For the record, I set the DIP sockets on the 6300 WGS in accordance with https://forum.vcfed.org/index.php?threads/at-t-pc6300wgs-motherboard-dip-switch-settings.23026/ so that it's on 80*25 monochrome mode and VDC400 card. It'll look even better once I put it all back together and bring out the matching keyboard and mouse.

Cheers, y'all!

I can try to help you. II have a lot of AT&T 6300's. However, Trixter, who s a member of this forum, has a website that has a lot of information on the AT&T platforms. For example, his observation on the WGS is given in the following link: https://trixter.oldskool.org/2012/05/27/data-preservation-case-study-att-6312-wgs/ In addition, here is Trixter's website: http://ftp.oldskool.org/pub/drivers/ATT/ The WGS is listed.

The picture you showed above is about normal output for the AT&T 313 monochrome monitor. The 25-D connector is standard for the 6300 and can support both monochrome, which you demonstrated, and color either by 318H or 319 monitors. Both of those monitors require external 110-V cords to display text as well as color. My display card in the 6300 presents an enhanced CGA but not EGA. So using checkit, I can see 600x200 resolution on the color as well as the monochrome monitor.

I can see from observing your picture that the WGS has a much smaller foot print motherboard in the cabinet and the power busses as well as communication busses have been replaced by the blue and white ribbon cable. I don't know if that directly feeds the VDC400 card or not. Obtaining the AT&T 318H or 319 color displays are at best difficult to buy because they are fairly scarce. Also users generally didn't take very good care of the monitors so many are fairly dark. I have on 318H that I believe has seen better days. So 1st1 makes a good point to find a VGA card and use a little more modern monitor.

I used MSDOS 6.22 on all my machines and found it quite good for most applications. UNIX is too slow and OS/2 is good but cumbersome as an operating system.

alejack12001 said:

I can try to help you. II have a lot of AT&T 6300's. However, Trixter, who s a member of this forum, has a website that has a lot of information on the AT&T platforms. For example, his observation on the WGS is given in the following link: https://trixter.oldskool.org/2012/05/27/data-preservation-case-study-att-6312-wgs/ In addition, here is Trixter's website: http://ftp.oldskool.org/pub/drivers/ATT/ The WGS is listed.

The picture you showed above is about normal output for the AT&T 313 monochrome monitor. The 25-D connector is standard for the 6300 and can support both monochrome, which you demonstrated, and color either by 318H or 319 monitors. Both of those monitors require external 110-V cords to display text as well as color. My display card in the 6300 presents an enhanced CGA but not EGA. So using checkit, I can see 600x200 resolution on the color as well as the monochrome monitor.

I can see from observing your picture that the WGS has a much smaller foot print motherboard in the cabinet and the power busses as well as communication busses have been replaced by the blue and white ribbon cable. I don't know if that directly feeds the VDC400 card or not. Obtaining the AT&T 318H or 319 color displays are at best difficult to buy because they are fairly scarce. Also users generally didn't take very good care of the monitors so many are fairly dark. I have on 318H that I believe has seen better days. So 1st1 makes a good point to find a VGA card and use a little more modern monitor.

I used MSDOS 6.22 on all my machines and found it quite good for most applications. UNIX is too slow and OS/2 is good but cumbersome as an operating system.

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I don't suppose you have a copy of AT&T UNIX for the 6300+?
I recently aquired a 6300+, and haven't been able to find ine install disks for it. My parents had a copy when I was young, but has long been tossed. I'm interested in doing some digging into how it was made to work on the 286.

Welcome to the forum @bluemantwo .

- Alex

bluemantwo said:

I don't suppose you have a copy of AT&T UNIX for the 6300+?
I recently aquired a 6300+, and haven't been able to find ine install disks for it. My parents had a copy when I was young, but has long been tossed. I'm interested in doing some digging into how it was made to work on the 286.

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No sir, I don't. You might post an inquiry and see if the forum membership might have something like that.

On Winworldpc see link (https://winworldpc.com/product/att-system-v-unix/2-x) is AT&T System V UNIX 2.x. However, according to Winworldpc the UNIX requires a 386 machine. There was a preceded type of UNIX call Coherent, which was according to the developers claims works on 8088, 286, 386 and 486 systems. The following link is to that website: http://www.nesssoftware.com/home/mwc/source.php.

By the way, does your floppy work on the 6300+? Do you have a 360-KB or 1.2-MB floppy? Mine will not work. There seems to be a problem in the daughter card on the motherboard.

Yes, that is definitively a M240. Here is a picture of mine: https://forum.classic-computing.de/gallery/index.php?image/82-olivettim240/

alejack12001 said:

By the way, does your floppy work on the 6300+? Do you have a 360-KB or 1.2-MB floppy? Mine will not work. There seems to be a problem in the daughter card on the motherboard.

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Unfortunately, I haven't messed with it enough to know yet. I don't have keyboard or monitor yet, only the PC itself. Trying to hunt down software before I spend more on hardware, and also want to take it apart and test the power supply separately before I fire it up.

Typical keyboards are AT&T 301/302. The AT&T 301 is probably the easier model to get as opposed to the 302. You can google the AT&T 301/302 as see what I am referring to. Monitors AT&T 313 is the monochrome; while the AT&T 318H/319 are enhanced color. All use the DB-25 pin connector. Power for the AT&T 313 comes straight from the CPU machine while the AT&T 318H/319 have the molded external power line similar to the power code of the CPU. Color is difficult to get and expensive.

You will need the keyboard as the POST will hang without it. A dot matrix printer could be substituted for the monitor. If you want to get around the internal video card you would need to extract the 74LS00 chip and substitute the jumpers as shown in the attached PDF on the video card. Sorry as far as I know there isn't a user or service manual for the 6300 Plus. You can use an 8-bit VGA card as the video after you render the internal video card disabled. I have both user and service manuals for the 6300. The attached came from the service manual for the 6300. I got a Western Digital Paradise video card with 256K RAM. It's not quite VGA it's more like EGA; but it works with a VGA monitor.

Depending upon where you attained your 6300+, you will find power supplies are weak. I personally put my hard drives outside of the CPU into a designed case with it's own power supply. I just ran the MFM cables out the back and made connections to the external case. My 6300+ has problem with the floppy drive either 360-KB or 1.2-MB that was he reason I asked. I have traced the problem to the daughter card in the flip side of the 6300+ CPU. The daughter card faces the motherboard and actions within the card seem to have an adverse effect on the floppy causing keyboard issues.

alejack12001 said:

I can see from observing your picture that the WGS has a much smaller foot print motherboard

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Here are some more pics of the inside of my system. The top side is basically a daughterboard consisting of 8-bit ISA slots. (Kinda disappointing it's not 16-bit - wondering if they sold weird proprietary 16-bit cards to go with yet another daughterboard.) And I promise that battery has come out since then - luckily that's on a daughterboard too!

alejack12001 said:

Obtaining the AT&T 318H or 319 color displays are at best difficult to buy because they are fairly scarce.

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I just managed to score a 319 on eBay! Unfortunately the picture is quite squishy, and it tends to turn itself off after some seconds - probably needs to be recapped and maybe some of the pots adjusted.

bluemantwo said:

I don't have keyboard or monitor yet, only the PC itself.

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I've got at least one extra keyboard. I picked up several other AT&T 9-pin keyboards (not 301/302s, they resemble generic 101-keys) from Computer Reset and they all seem to work fine. Let me know if I can send one your way, or if you'll be at VCF Southwest next month. They might be regular serial keyboards, but I'm not sure if that's true.

The M240 has no 16 Bit slots like M24 did, because they were totally useless besides some Olivetti cards (Graphics card as a "u-board to connect the mainboard with the bus-converter (ISA-slot card) and memory cards). The M24 16 Bit slots were proprietary and not compatible to the AT 16 Bit standard.