Re: The near-mythical IBM color MDA
It only supports mode 7 since it's an MDA card. :) The QBASIC COLOR statement doesn't bother to range check the arguments, it just copies them into the attribute byte in video memory. This is why the trick works. Other programs *know* that you clearly have a monochrome card so they won't use the full attribute byte even though they can. If you manually poke values into the BIOS data area (0x449) to indicate mode 3, then programs will start writing to 0xB8000 instead of 0xB and you won't see anything on the screen. I thought about it some more this morning, and I realized that the video memory on the MDA card has a memory address decoder (actually a 'LS138, U51). By pulling pin 1 of the chip and tying it to ground, I was able to alias the MDA video memory at 0xB8000 as well as the normal 0xB location. When I poked 3 to 0x449 using DEBUG, it actually worked, and I got QBASIC up in color! https://twitter.com/TubeTimeUS/status/1033028673970921472 There are a few strange effects, naturally. QBASIC reprograms the cursor incorrectly so it appears in the middle of the character cell. Also, because the underline generator still uses the attribute byte, dark blue text appears underlined. On Thu, Aug 23, 2018 at 8:49 PM Fred Cisin via cctalk wrote: > OK, so the demo was with a "MODIFIED" card. :-) (admittedly a trivial one > that brought it in line with published schematic) > > Which Int10h modes does it support? > QBASIC is presumably simpy using the INt10h modes. > The MDA by default was in Mode 7. > If it will do mode 3, then it can do Lotus in color, etc. > > Obviously, it doesn't have the RAM to do any "high resolution" modes, . . > . > > > > On Thu, 23 Aug 2018, Eric Schlaepfer wrote: > > > I'm not that lucky! But yes, an early card with the light pen connector > > should work. > > > > The card I used for the demo is a somewhat later revision. I added rework > > wires to match the schematic in the technical reference manual of the > > earlier revision. > > > > With either an early MDA card or a modded card, if you fire up DOS 5.0 > and > > have QBASIC, you'll find that the COLOR statement... just works! It's > quite > > strange. > > > > On Thu, Aug 23, 2018 at 8:24 PM Fred Cisin via cctalk < > cctalk@classiccmp.org> > > wrote: > > > >> On Thu, 23 Aug 2018, Ali via cctalk wrote: > >>> Which revision MDA is this? I have an original NEC Multisync and I have > >>> a tone of MDA cards including one in one the first 5000 IBM 5150s > >>> produced. I would love to get color out of it just for the sake of > doing > >>> it. Do you still have your demo programs? > >> > >> Do any of yours have the 6 pin Berg connector near the top of the > mounting > >> plate? Some did. On CGA, that connector is for light pen. > >> Supposedly some early MDAs had pins 3,4,5 connected (not connected in > >> later ones). That MIGHT be the same ones as have the light-pen? > >> connector. > >> > >> https://www.seasip.info/VintagePC/mda.html#cmda > >> > >> http://www.minuszerodegrees.net/5150/early/5150_early.htm >
Re: The near-mythical IBM color MDA
Correction--it wasn't Glitch who got the pen, it was Trixter. I have trouble with pseudonyms. --Chuck
Re: The near-mythical IBM color MDA
On 08/23/2018 08:31 PM, Eric Schlaepfer via cctalk wrote: > I'm not that lucky! But yes, an early card with the light pen connector > should work. > > The card I used for the demo is a somewhat later revision. I added rework > wires to match the schematic in the technical reference manual of the > earlier revision. I had the original MDA and a rather ancient light pen from some graphics console or another. I hooked it up to a 6-pin Berg header and got it to work, sort of. I didn't use the interrupt 10h BIOS functions, though, but rather accessed the 6845 registers directly. The operation was pretty terrible. The medium-long persistence of the monochrome monitor led to large positioning errors. I recently sent the pen to Glitch, who hasn't gotten back to me to report wether it still works. It was pretty nice with a pressure-activated tip swich with fiber optics coupled to a phototransistor, with a couple of transistors to boost the signal. Black with a coiled cord--6 conductors, I think. --Chuck
Re: The near-mythical IBM color MDA
OK, so the demo was with a "MODIFIED" card. :-) (admittedly a trivial one that brought it in line with published schematic) Which Int10h modes does it support? QBASIC is presumably simpy using the INt10h modes. The MDA by default was in Mode 7. If it will do mode 3, then it can do Lotus in color, etc. Obviously, it doesn't have the RAM to do any "high resolution" modes, . . . On Thu, 23 Aug 2018, Eric Schlaepfer wrote: I'm not that lucky! But yes, an early card with the light pen connector should work. The card I used for the demo is a somewhat later revision. I added rework wires to match the schematic in the technical reference manual of the earlier revision. With either an early MDA card or a modded card, if you fire up DOS 5.0 and have QBASIC, you'll find that the COLOR statement... just works! It's quite strange. On Thu, Aug 23, 2018 at 8:24 PM Fred Cisin via cctalk wrote: On Thu, 23 Aug 2018, Ali via cctalk wrote: Which revision MDA is this? I have an original NEC Multisync and I have a tone of MDA cards including one in one the first 5000 IBM 5150s produced. I would love to get color out of it just for the sake of doing it. Do you still have your demo programs? Do any of yours have the 6 pin Berg connector near the top of the mounting plate? Some did. On CGA, that connector is for light pen. Supposedly some early MDAs had pins 3,4,5 connected (not connected in later ones). That MIGHT be the same ones as have the light-pen? connector. https://www.seasip.info/VintagePC/mda.html#cmda http://www.minuszerodegrees.net/5150/early/5150_early.htm
Re: The near-mythical IBM color MDA
I'm not that lucky! But yes, an early card with the light pen connector should work. The card I used for the demo is a somewhat later revision. I added rework wires to match the schematic in the technical reference manual of the earlier revision. With either an early MDA card or a modded card, if you fire up DOS 5.0 and have QBASIC, you'll find that the COLOR statement... just works! It's quite strange. On Thu, Aug 23, 2018 at 8:24 PM Fred Cisin via cctalk wrote: > On Thu, 23 Aug 2018, Ali via cctalk wrote: > > Which revision MDA is this? I have an original NEC Multisync and I have > > a tone of MDA cards including one in one the first 5000 IBM 5150s > > produced. I would love to get color out of it just for the sake of doing > > it. Do you still have your demo programs? > > Do any of yours have the 6 pin Berg connector near the top of the mounting > plate? Some did. On CGA, that connector is for light pen. > Supposedly some early MDAs had pins 3,4,5 connected (not connected in > later ones). That MIGHT be the same ones as have the light-pen? > connector. > > https://www.seasip.info/VintagePC/mda.html#cmda > > http://www.minuszerodegrees.net/5150/early/5150_early.htm >
RE: The near-mythical IBM color MDA
On Thu, 23 Aug 2018, Ali via cctalk wrote: Which revision MDA is this? I have an original NEC Multisync and I have a tone of MDA cards including one in one the first 5000 IBM 5150s produced. I would love to get color out of it just for the sake of doing it. Do you still have your demo programs? Do any of yours have the 6 pin Berg connector near the top of the mounting plate? Some did. On CGA, that connector is for light pen. Supposedly some early MDAs had pins 3,4,5 connected (not connected in later ones). That MIGHT be the same ones as have the light-pen? connector. https://www.seasip.info/VintagePC/mda.html#cmda http://www.minuszerodegrees.net/5150/early/5150_early.htm
RE: The near-mythical IBM color MDA
> > The NEC Multisync monitor thread reminded me that I used one to produce > a > video, and I thought a few of you might enjoy it. > https://www.youtube.com/watch?v=-TiHFWH4NWk Eric Which revision MDA is this? I have an original NEC Multisync and I have a tone of MDA cards including one in one the first 5000 IBM 5150s produced. I would love to get color out of it just for the sake of doing it. Do you still have your demo programs? -Ali p.s. What other secrets did the original MDA card have?
Re: The near-mythical IBM color MDA
Nice! 2018-08-23 23:29 GMT-03:00 Eric Schlaepfer via cctalk : > The NEC Multisync monitor thread reminded me that I used one to produce a > video, and I thought a few of you might enjoy it. > https://www.youtube.com/watch?v=-TiHFWH4NWk >
The near-mythical IBM color MDA
The NEC Multisync monitor thread reminded me that I used one to produce a video, and I thought a few of you might enjoy it. https://www.youtube.com/watch?v=-TiHFWH4NWk
