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newly acquired Leading Edge Model D - monitor cable and IDE/CF help needed

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chris2fett

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Mar 19, 2023
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Newbie here! I grew up with C64/Tandon PC-XT clone/286 clone / 486... etc through modern machines today, and recently decided to dip my toes back into the retro PC community with my "dream" machine... a Leading Edge Model D -2011, with 640KB RAM and 2 floppy drives. Just the desktop is included; no keyboard, no MS-DOS disks, no manuals, no monitor. Per the seller, the machine does power on and goes through the full 640K memory check, then fails to find a boot disk.

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So, I've got a few semi-urgent questions and would LOVE any recommendations/advice!

1) The Daewoo motherboard is a custom design, and has integrated monochrome and CGA color graphics via two separate 9 pin monitor connectors (see photo). Since I do not have a CRT, I plan to connect this to a standard LCD monitor 15 pin VGA DSUB connection. What type of adaptor and/or cable should I purchase? I am very confused researching this online, as many cables and or/adaptors sound like they are used for serial data transmission rather than video signal(?)

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2) I've LOVE to have an XT-IDE CF type device for the 8 bit ISA bus (no hard drive included), but after online research and YouTube video reviews, I am still uncertain if this will even work with my Daewoo motherboard. Specifically:
a> It appears that I need to get MS-DOS or PC-DOS 3.2 or 3.3 to get the thing installed, but that limits my CF size to 32 MB. Higher versions of DOS seem to have more issues with initial installation? But the CF partition can hit 2GB. I would love DOS 5 or 6.2, but I am trying to avoid the memory overhead in a 640K system
b> CF cards are very finnicky and some work/some don't/trial and error approach, is this correct?
c> Do I even need the plug-in card XT-IDE with bios IF my Daewoo motherboard already has an IDE hard drive controller port? Could I not just plug my CF into the small passthrough adaptor, directly into the motherboard?


THIS is what I was first thinking I would need... an 8 bit ISA card with it's own XT-IDE BIOS installed, and built in CF adaptor
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....but would something like THIS be enough fo an XT class PC?
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1. You'll need an active adapter like an MCE2VGA or RGB2HDMI (with an HDMI to VGA adapter) as the MDA/Hercules and CGA signals are digital TTL at a horizontal sync of 18.43KHz (MDA/Hercules) or 15.7KHz (CGA) while VGA is an analog RGB signal at a horizontal sync of 31KHz.

2a. There's also the option of using Compaq DOS 3.31 which supports FAT16 (up to 2GB) partitions but is closer to DOS 3.3 as far as overhead and compatibility.
2b. Haven't had to buy new CF cards in a while but most good name-brand cards should work
2c. The hard disk connector on that motherboard is probably for an XTA hard disk which is not compatible with IDE/ATA (which is what CF cards are and what those passive IDE to CF adapters are intended for.) You will need a card like the XT-IDE or XT CF to use CF cards or standard IDE disks in an XT-class system.
 
Thanks for the advice! Unfortunately, it looks like the MCE2VGA is no longer available/sold :(

Am I correct to assume that: I could insert an 8-bit VGA card (or backwards compatible 16-bit VGA card into an open ISA 8 bit slot) and use the 15 pin VGA out "normally" to a modern LCD with 15 pin D-sub input. I would just need to figure out how to disable the onboard MDA/CGA graphics if possible on the Daewoo board, correct?
 
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The Leading Edge Model D does not have any onboard hard drive controller, and watch out for the clock battery which is prone to leaking. See Adrian's detailed video about the machine if you haven't already:

 
chris2fett said:
Thanks for the advice! Unfortunately, it looks like the MCE2VGA is no longer available/sold :(

Am I correct to assume that: I could insert an 8-bit VGA card (or backwards compatible 16-bit VGA card into an open ISA 8 bit slot) and use the 15 pin VGA out "normally" to a modern LCD with 15 pin D-sub input. I would just need to figure out how to disable the onboard MDA/CGA graphics if possible on the Daewoo board, correct?
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MCE2VGA is difficult to get lately due to the FPGA shortage. RGBtoHDMI is available but more expensive.

Yes, you can use an 8-bit compatible VGA card. If you cannot disable the onboard graphics, then set it to monochrome (MDA can coexist with VGA, but CGA cannot). You may need to run "mode co80" at startup to switch DOS to the VGA output.
 
vwestlife said:
The Leading Edge Model D does not have any onboard hard drive controller, and watch out for the clock battery which is prone to leaking. See Adrian's detailed video about the machine if you haven't already:

Click to expand...
Thanks for the reference! Yeah, I'll have to deal with that battery somehow. I saw Adrian's review when he when he first posted it a while back. Adrian didn't fully realize what a treasure he had there! I though aboutt contacting him to purchase the machine, but then learned a few months ago that he provided it to a friend in the Portland area :(
 
Plasma said:
MCE2VGA is difficult to get lately due to the FPGA shortage. RGBtoHDMI is available but more expensive.

Yes, you can use an 8-bit compatible VGA card. If you cannot disable the onboard graphics, then set it to monochrome (MDA can coexist with VGA, but CGA cannot). You may need to run "mode co80" at startup to switch DOS to the VGA output.
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That's great information! Fortunately the Leading Edge has an external toggle switch for the MDA and CGA ports.
Looks like legit VGA 8 bit cards are mega $$$ online right now, so I'll have to find a 16-bit compatible model; these seem to be cheaper.

The handful of original Leading Edge monitors for sale on eBay right now are untested and look like they went through a war zone!
I am not sure of any other mid/late 80's era monitors that would be compatible (Apple? Commodore?), and there's ALWAYS the problem of shipping a CRT and getting it in on piece.

The MCEtoVGA is no longer manufactured and is sold out.
Ambery is sold out of their CGA to VGA adapter/converter box.
Texelec does currently have some RBGtoHDMI adaptors available. Pricey, but may ultimately be my best option.

I've got a buckling spring Unicomp Model-M PS2 keyboard for which I will purchase an active adaptor ~ $25 on eBay to connect to the Model D.
(We all know how much the original Leading Edge blue Alps switch Model-F style keyboards go for $$$$ !)

Texelec ALSO sells an IDE to CF ISA 8 bt card, as well as an SD card version. Not sure which would be "better" overall. Any opinions?

Everyone here has been EXTREMELY helpful!
 
FYI it looks like you can disable the onboard graphics by removing the J10 jumper.
 
vwestlife said:
VGA can coexist with CGA, but only if the card is run in MDA emulation mode, which not all cards support.
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That's not really coexisting though. If you have a video card configured to emulate MDA, then it's no longer CGA...
 
Timo W. said:
Get a Trident TVGA9000. Everybody hates those, but they are great for slower systems and work just fine in 8-bit mode.
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Cirrus Logic CL-GD501 or Acumos AVGA1 also work well in XTs and can often be found cheap.
 
Plasma said:
That's not really coexisting though. If you have a video card configured to emulate MDA, then it's no longer CGA...
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I meant the VGA card has to be in MDA emulation mode. Hercules "half" mode emulation should work as well, if your VGA card supports it.
 
I see what you are saying but I think it's a matter of perspective. Is a video card with no VGA modes but VGA output still a VGA card? :unsure:
 
Yes, since VGA is both a graphics standard and a display connector standard.

I mean, if you have a VGA card and start a game running in CGA mode, is your VGA card no longer VGA then? Of couse not. It is still outputting a VGA signal for a VGA monitor.
 
Right, but in the case of a VGA card configured for MDA/Herc emulation alongside a CGA card, no VGA modes are possible. You cannot run any programs requiring a VGA card. It's only a "VGA card" in the sense that you can use a VGA monitor. If you attach MCE2VGA to a Hercules card, does that become a "VGA card"?
 
Timo W. said:
Get a Trident TVGA9000. Everybody hates those, but they are great for slower systems and work just fine in 8-bit mode.
Click to expand...
Thanks for the suggestion! After perusing eBay, it looks like there are a few variants of the chip, a 9000 A, B, C, etc. Do you know if this matters, or if the manufacture of the card has any role to play with compatibility as long as the chip is the TVGA9000?

It will be weird, but what I’m hoping to do is: plug the VGA card into an eight bit ISA slot, use a 15 pin VGA connector to hook it up to an LCD monitor, turn on the computer and at least get a picture. Unless I buy an old monochrome or CGA monitor, or a $100 plus active adapter, I will have no way to see what I’m doing, trying to get to VGA card to work.
 
Any 9000 will do. They all work in 8-bit mode.

The only thing I'm not 100% certain about is if any of them may need a 286/V20 CPU to execute their BIOS. But given they all have jumpers for a dedicated 8-bit mode, they should work with a 8086/88 CPU.
 
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