This is a tricky one. Everywhere I've read indicates that the onboard video will outrun any Nubus card that you stick in your Quadra. I wanted to play around with the 5 free slots and so purchased (very blindly) a Supermac '7831-0001' from eBay. The item was actually listed as a 'sound card', which didn't make too much sense as the image definitely showed a video card with a db-15 connector. The description then mentioned that it was a 'NuBus Thunder Graphics Card'.
I'd read from the odd forum online that the "Thunder IV" card from Radius/Supermac could out-perform the onboard graphics, but they were as rare as hens-teeth. After a little searching, it turns out that I'd actually purchased a Supermac Spectrum/24 PDQ+ (ROM v1.292). Here's a list of old video card drivers and manuals that I also used to get this relic operational.
Trying to find the original information for this card was a challenge. The Supermac site (thanks to the wayback machine) has nothing on their video card range. The earliest snapshot is from 1997, 5 years after this card was made. There isn't even a single Wikipedia page for the company. A little more digging shows that Radius bought Supermac in 1994. That would explain why the snapshot of their website only shows the Mac clones; Radius took all the graphics cards and re-branded them, leaving just the mac clones under the Supermac name (in fact, they licensed the 'Supermac' name to UMAX Technologies, another clone creator.) Of course, when Jobs got back to the helm, he obliterated the clones.
The Radius site on the Wayback Machine indicates that they kept support running for the Supermac video cards, but I can't find reference to any hardware upgrades. Read here for the history of the Supermac company. And here's some news articles from back in the day: Radius and Supermac merge, Video Graphics Companies Agree To Merge In Stock Swap, Supermac may return as clone seller and Apple Squeezes Mac Clones Out of the Market.
It's a huge card; reminiscent of a full-length VESA/VLB card from the 486 years. None of the numbers on the board match to the great list of Nubus Video Cards found here. I initially thought it was a 'Thunder', relying on the information from the eBay auction. After a little research via Google Images, I then determined that it in fact was a Supermac Spectrum/24 PDQ+. Turns out this card can do some high colour depths, Gamba's website indicates that it is capable of up to 1152x910 @ 24-Bit (His site also has the Supermac software for download!)
Installing this card was very straight-forward. It didn't seem too secure in the slot during my testing, but I assume the side-panel of the Quadra case secures it correctly. I had left this off during the entire process. There is also a hook on the face-plate which seems like it should lock in somewhere. I'm wondering if I'm missing a part of the Quadra's case.
Above, you can see the opened case, a close-up of the slot cover-plates from the inside and then a cover-plate removed. From the second picture, you can see the tab that needs to be pushed clear of the frame. Once done, the plate will easily slide out the back of the case.
Once plugged in, I left the video on the internal video port. The MacOS logo came up, but it didn't proceed any further. I then forced a shutdown and plugged the video into the Supermac card. It booted up in 2-bit colour! I could straight away switch to 'Millions of colours'. Unfortunately, the onboard video could already do this thanks to the upgraded VRAM.
There's a FAQ here for more information on these cards. There's also a good article here which actually indicates that, as at 1992, the Thunder/24 (yes, I have the Spectrum, but when I found this I thought I had a Thunder) is a great match for the Quadra series for desktop publishers wanting (and I quote) "a really screaming solution for serious color-graphics professionals."...
"The combination of Quadra and SuperMac Thunder/24 provides a really screaming solution for serious color-graphics professionals," said Scott Billups, presidentof VIZ-Ntr, a computer-graphics production firm. "I can't imagine why users requiring the power of the Quadras will want anything less than fast, large-screen, 24-bit true color."
Nubus with PPC Upgrade
Having the graphics card up and running, I thought I'd then see how it went with the PPC Upgrade. During a 'warm restart', the LCD stays on and you get to see the "S" in the bottom-right corner of the screen in red. It's the BIOS of the card; the Supermac logo.
After this, the standard grey pattern of the boot screen is meant to show, and it did, but things weren't looking too healthy. The grey appeared... but it took around 1 second to draw the screen from top to bottom... i.e. you could see the individual pixel lines being drawn down the screen. The MacOS logo then appeared and also had the horizontal drawing slowness.
It seems that the PDS PPC card cannot get the data to the Nubus Video card quick enough. I didn't bother trying lower resolutions. This was in System 7.6.1, so I'll try a newer version later. Here's a use-net post of a user having the same problem. It seems we need to upgrade the ROM on the card... where the hell would we find that nowadays? There's a Q&A on the Vintage Mac World site stating that this is the requirement... the PDQ+ can support a PowerPC, but it needs a ROM v3.0 or higher.
Rom Upgrades for the Supermac Spectrum/24 PDQ+
As luck would have it, a user over on the Amibay forums happens to have the ROM available for purchase. He's made an image himself and is capable of burning EPROMs identical to the "Supermac Spectrum/24 PDQ+ ROM Upgrade Kit v3.1" (note that I cannot even find a reference to this anymore!) I purchased both a burnt ROM and the image from him. I also purchased an EPROM burner (not to be confused with an EEPROM burner, this isn't new tech we're dealing with!) from eBay and some extra 27C512 EPROMs ... just in case.
The ROM Upgrade has arrived and is installed. I also upgraded to the SuperVideo 3.1 software which can be found here. The result is that you get a new control panel in Monitors and Sound and can select pre-set monitors and resolutions... now that I have the old and new firmwares to compare I can start digging in to see if I can't output a custom resolution.
Startup Shortcut Keys
It turns that, if you're quick enough, you can hold down OPTION at boot time and get a resolution selection screen. ... I'll try this whilst I'm upgrading the ROM.
Making the card output a higher resolution?
I'll start a new post on this... I think it'll take a bit of work... Will update this post at a later date with more information...
DSP Addon Cards?
Digital Signal Processors are hardware chips designed for specific data processing. They were popular in the 68k Macintosh computers for providing added power to video/photo processing applications such as Photoshop. The applications needed to be coded to support the additional hardware. There seem to be quite a few available on eBay, but I've no real software capable of using them and wouldn't know where to start.
Macintosh to VGA Video Adapters
Vintage Macintoshes use a DB-15 plug for video cables. Back then, the PC world was already up to HD-15 VGA plugs. Converters can be purchased and are usually brand-less with no markings. It gets more confusing: the dip-switch settings on them are varied between manufacturer, so be careful when adjusting the settings.
My Quadra 950 came with a 10-switch converter. Searching google, I found three different pages with differing descriptions of how the switches should be configured. I have a Samsung 913v LCD capable of 1280x1024. Setting the switches to 1-5 on and 6-10 off gives me a blurry 1152x870 fixed resolution. Trying to get it to display 640x480 has been a challenge.
Note: at any point in time, if your machine boots to no image, wait for disk activity to stop and then hit the keyboard power key. Pressing the enter key on the numeric keypad will shut down your machine cleanly. This made for some very long resolution testing cycles with 256mb of RAM!
I first tried the switch settings described here. As that the adapter was on "12345" to start with, I guessed that my monitor happily supported "Mode 1". I therefore tried to get 640x480 (this is all for a game, btw) via setting "235". On boot, the LCD would not display the image. I don't see why not though... it's supposedly 'VGA 640x480'. Maybe these were the wrong instructions for my adapter.
The settings displayed here state '57' for 640x480 VGA and they don't work... monitor doesn't turn on.
Next attempt was the settings at the bottom of this page. Bad photocopy, but they can be made out. But they're the same as the first setting list.... Just for fun, I tried 'Mode 2' '2356'. This showed an image and gave me the choices of 640x480 and 800x600, but it was stuck on the latter and I couldn't actually switch to 640x480. I didn't want 800x600. At this point I left the machine running and yanked out the cable, adjusting the settings to "14589" for "Multi-sync 14". 640x480 came up on the reboot! And thanks to the warm reboot, I didn't have to wait for years. This setting implies multiple resolutions but only allowed 640x480... wrong settings matrix for this adapter?
I tried "14678" because I saw it on the blog post here. It seems the blogger had it working as a multi-sync resolution... I only got 640x480.
...so confusing... Might be time to purchase an adapter that comes with a known dip-switch setting manual.