XGA : King of IBM Graphics Standards (Part 1) 

I can't believe I just watched a 40minute video about XGA, and I look forward to the next one :) As a kid I always saw the words XGA almost everywhere, but never seen a true XGA machine

Fascinating stuff. I thought I knew the history of PC pretty well, but I never heard of this particular -GA.

Thanks for making all of this content. It's everything I've been wanting to learn about old PC video. Whenever you're about to exercise some obscure functions using registers nobody ever touches... time to grab the popcorn.

Hey, just discovered your channel. Love the content. I am 41, and the old school nature of it is pure nostalgia to me.

A datasheet for a video IC, don't see that anymore these days, lol Great video as always!

Now I understand why the Amiga platform was popular for games and creative purposes.

Excellent video, like with VGA it seems XGA was reduced to marketing speak for a resolution.

The microchannel adapter shown @<a href="#" class="seekto" data-time="199">3:19</a> (FCC ID ANO4AR1887972) is actually the IBM 8514/A (see the pictures and outlines at the 'Ardent-Tool' - If you have a system to run it in, I can send one for the cost of shipping). Of course, the IBM versions of XGA (AKA "XGA-1" and "XGA-NI", for "Non-Interlace") and XGA-2 are at the 'Ardent-Tool', too. XGA also exists on the 8590/9590 (Model 90) planar, and XGA-2 on the 9533 (Model 'E', and ISA system) - sadly never more than 1Mb VRAM. Really, I do have extra 8514/A, XGA, and XGA-2 adapters - Find a 9590 (which had an XGA-2 adapter installed with inactivated XGA on the planar, blue badge), and I'll send you an 8514/A adapter; You would have a system for all three standards.

You're videos are really interesting. Thank you!

I did some XGA programming many years ago for a software which did a data visualisation. It don't recall it being fun or easy getting the code which setup the adapter in a display mode to work on clones from different manufacturers. I never touched a real XGA, but in practice I think most computers had a clone. I know when setting a display mode, you had to do things in a very specific order, or it just wouldn't work. In your video you say like there are no 16/256 color or monochrome modes listed. However I am pretty sure the PL4 is just that, "P(alette) L(inear addressing) 4(bits)", which is 16 bit color. This means that there are two pixels stored in one byte. The P8 is 256 color palette mode. You could find out if a monochrome monitor was connected by reading some register. If so, you wrote two of the colors as 0 in the palette and put the greyscale value in the third. I am pretty sure that was done with R and G being 0 and B being the value. I think the trick to getting palette modes working was setting XGA mode, disabling the palette (which was also sometimes referred to as blanking display for reset), loading the palette, and enabling the palette (sometimes also called normal mode). I think most cards needed a specific "palette" loaded if they were in direct color mode, however I didn't use that mode at all. I had used an array of 48 or 768 8bit values depending on if I was doing 16 or 256 color modes. Monochrome was not supported for my software, so I just checked if the connected display monochrome, and if so I made the program exit. You made a remark that there are two modes which work the same, but the display moves over. I would guess that they are different timings. Do you know which monitor types should be supported by your card? Does it have support for interlaced and non interlaced? If the mode which is shifted might be the non interlaced mode, which would have faster timings. You would probably need an oscilloscope to determine what is really going on with the signal. I sadly I don't have the code from that software anymore. I had last loaded it onto a "Smart Media" card, which turned out not being smart at all, as I couldn't read the media only one year later.

Great video! I'm already eagerly awaiting part 2. Transparency effects (for fog, water, light...) for games in low resolutions (320x200 16bit) would be particularly exciting.

Thank you for another super interesting journey!

It is entirely true that XGA was the high-end standard at the beginning of the 1990s. Unfortunately, as with MCA, IBM was adamant to force an unnecessary market segmentation that delayed adoption of the standard. While it is true that a minimum of 1MB of RAM and other performance requirements were pretty high, IBM did not help either by focusing on creating another standard without cooperating with the rest of the industry during development or after that. Luckily, due to market demand, the XGA eventually became the standard by 1994 and you were hardly pressed not to find a graphics adapter having 1024x768 in 256 colours capability. Funnily enough, most affordable colour CRT monitors in 1993-1994 were only able to use that resolution in 43Hz interlaced mode and with a 1MB video card you could not ask any higher refresh rate in 256 colours. Oh, fun times before we had the Multisync monitors in the mainstream... All of this resulted in a lag of a couple of years before XGA was available end-to-end on the PC market.

XGA used to have its own wiki page, but given how it can be edited by anyone, someone decided to change it to just the video resolution years ago. BTW, the original XGA cards only had 512kB of VRAM (I had one in my PS/2 Model 95 until I upgraded it to an XGA/2 planar.)

Interesting video! Had no idea about the xga co-processor, it could’ve been so much more..

The alternate resolutions like 800X600 were driven by the laptop LCD market. LCD's are one of the major COGs for laptops and this is the period where laptops are starting to displace desktops in volume. An ancillary market was of course LCD projectors which also were becoming core tech for sales road warriors. Brooktree really opened up the market with this aggressively priced high speed flash DAC. Rockwell (who owned the modem market at the time) bought them out. This is the period where the DAC was external. The Accellerator/XGA was purely BiCMOS digital and the DAC did the video output. I seem to recall that around this time 3Dfx was making a name for themselves with low cost daughter boards that made your PC a great gamer. These were cards where your VGA was looped through the 3Dfx card input to output and overlayed the graphics using the VGA's sync capability. Very very cheap upgrade and worked really well. And they were so fast that this product just died a very quick death. OF course next was integrating the two cards into one Radeon, Voodoo, GEForce.

The Windows icon and cursor formats use a Xor mask and an And mask in such a way that it seems like it was created to match these sorts of accelerators (or maybe the other way round). I never really thought about why those formats seemed a little unusual for something that was only really used for colour and 1 bit transparency.

many years ago, i worked at ibm argentina, in a pile of garbage i found several boards like the one you show in your video, which is unobtainable, since i didn't know what it was but if i had seen the dram chips i brought only that part, even the I have, now it is an ornament. I remember there were many of those plates in the trash.

Crazy how IBM invented blitter-like functionality in a PC graphics adapter and everyone just ignored it, even though people like IIT sold cloned or maybe even licensed chips and people like Hercules built them into cards. Then a bit later S3 invented it again and sold piles of chips to a bunch of graphics card OEMs. It's almost like it went from 'No one gets fired buying IBM' to 'Ignore IBM even when they come up with decent ideas'. Maybe XGA was patented and IBM tried to charge too much for people like IIT to implement it which meant only companies like Hercules used the chips. As far as I know S3's accelerated VGA chips were pretty cheap. Also S3 was very optimized for the Windows GDI. So your list boxes were very fluid even if you had a slow CPU and an ISA bus. And because no one really cared about register compatibility it meant S3 could just provide a Windows driver and not have to worry about keeping a register level interface compatible across successive card generations. Then of course 3D came out and everyone programmed at the DirectX or OpenGL level and companies like NVidia never actually documented the register level interface to their GPUs.

"Object shading" sounds like it might allow polygon filling in 16bit mode where different colours are specified for each vertex, and then blended based on the pixel position in the polygon? That would effectively allow Gouraud shading which would have been really nice for 3D fills. From my experience with 16bit colour in DirectX 2 later in the 90's, there were various formats. RGB 565 was the most common, but we also came across 556 and even 664 on some strange cards. (Plus some that cheated and used 555 so were effectively 15bit rather than 16) Some also supported alpha channels like RGBA 5551 for 15bit colour plus basic transparency or 4444 for 12bit colour with 4bit alpha blending. It's interesting to see how the various low-level operations were starting out on cards like this. These all ended up getting rolled into DirectX (or specifically DirectDraw) later on. (Plus functions to interrogate all the various cards to see what they supported)

Great✌

Your card has MT RAM chips, these are well known for failing and could be the cause of your boot and corruption problems.

Interesting, never heard of the XGA features before. Seems to be highly inspired by the the Amiga blitter, though.

I thought, XGA is just the 1024x768 display resolution until I saw this video!

Although none of this is at all relevant to me, I find it so interesting that I had to watch, and I think I even learned a few things! I'm just so amazed that anyone at all is producing videos about these old technologies, and even more so at the lack of information available. Your quote that "that's a problem I'm not going to be able to solve, at least not this week" perfectly sums up the way many people working on this old stuff today feel. 😅 Also, your video on the Deskpro has inspired me to buy a 486/33M model with EISA. Should be picking it up tomorrow and it was a bargain!

I see you have an electronic copy of Ferraro? How did you come by it? Is it available somewhere? I only have a hardcopy, which is a bit cumbersome nowadays 😄.

Hmm. I know from the experience of having used Fractint that just because all the "known" resolutions might be listed on the two pages thry left out of the book, the real capacity of the card would likely involve a mess of other, "undocumented", ones, some undocumented purely because they where not in the sales documentation. So glad this stuuf is either now uncomplicated, or hidden so well you can't even force them into some off mode in the OS, trying to work out wtf you actually could do, in terms of color or resolution, even if you knew how, was a massive pain, and its not like you could ask the card - just try and hope it didn't crash/break something.

I feel like I might stumble onto this rotating Polyhedra somewhere in the backrooms.

Really enjoyed this. Would love if there's code resources so I could assemble and fiddle around on my PS/2 system.

I'm surprised these aren't all microchannel

I thought colour depths of 15bpp or more were always "direct colour"? I've never heard of a card/chipset/computer with 65536 palette registers.

Funnily enough I think I have two xga2 microchannel cards. Now one day I need to repair the ps/2 that broke (in seemingly the same way as curious marc's one of the same model)

<a href="#" class="seekto" data-time="138">2:18</a> 1992, week 41 for the chip.

<a href="#" class="seekto" data-time="405">6:45</a> incredible 75MHz refresh rate! just unbelievable what they archieved back then with what little we had ;-)

awesome knowledge

I'm surprised IBM has lasted so long. They seem to have more flailed products under their belt, than successful. It's like they exist solely to invest in all the R&D for the rest of the industry to clone (or take the best parts to make something better or cheaper). Always wondered why they didn't license their technology out, rather than trying to be so proprietary. I could almost say the same about Apple, although they don't seem to be nearly as affected....not sure what they do differently.

I'm not sure if my previous comment got deleted or not, but I have a book from 1995 with about 106 pages on XGA. I had an imgur link to the pictures of the cover and table of contents, but I think the link may have nuked my comment.

What above 86.958 Hz interlaced refresh rate? It shows 43.479 full frames.

Anybody else tried to wipe that yellow dot off the monitor or just me?

my PS/2 57 (not installed yet( should have XGA2 :)