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SuperMac Spectrum/24 Project


Thanks for popping back in, bud!

I spent some time digging around for that thread, to no avail. Apparently I'm just not good with the search engine terms today.
I forgot, what's the switch on Google that limits searches to the MLA? Their bot has scraped up whatever it's wanted here since the dawn of time. Searching just this site a/o the archives using Google, DuckDuckGo etc. could be a workaround for searching lot of our broken linkage and topics?

Search methods like that on current engines might make for a good topic somewhere?


Well-known member
The Spectrum 24 Series III doesn't show the custom resolution option in the drivers I tested, so sadly that is the end of that experiment, unless I can work out another way of adding resolutions.

Ah well.


SwitchRes I've heard much about, but never tried. My card is flat out, baseline Spectrum 24 with a redonkulous amount of customization available for virtual desktop, but limited to something like 1024x768 output or less on the connector by the RAMDAC as I understand it.


Well-known member
I suspect that SwitchRes wouldn't work - I anticipate that the Supermac control panel sort of loads new microcode into the card itself... SwitchRes would need to be designed to specifically work with the hardware in that card.


First part of @Gorgonops great rehash of old thread:
Anyway, FWIW, my vague memory of the takeaway from that discussion was that the architecture of the 24 bit versions of these cards (the 3MB RAM models) is essentially as if you stacked up in parallel three 8-bit 1MB cards. IE, the issue with Trash's dream of outputting the mega-high (virtual) resolutions that in terms of raw pixel count could fit in 3MB is the output circuitry can't "chain" the memory on those three planes together. So, for instance, even if you stuck an oscillator in there that ran fast enough for a 1920x1080P mode's pixel clock (and somehow didn't melt the RAMDACs, given their maximum rated clocks are only a little over half what's needed for that) because the math tells you that doing 8-bit at that resolution only requires 2MB (a little less, actually) of RAM that card still won't be able to push it because in 8-bit mode it can't access more than 1MB.

Middle part, heart of the info:
Technically, yes, the bandwidth is there, IE, at 1024x768@24 bit it's throwing more *memory* out the back door per second than it would be at 1920x1080@8, but it can't throw that many *pixels* out. If you wanted to rip off the RAMDACs that are there and design new output circuitry that takes the three color planes for a 24 bit mode into a latch and then clocks them out as three 8-bit pixels through a faster RAMDAC (essentially clock-tripling the card to trade depth for pixels) then I guess that would probably be... possible? But it'd come at significant price. I don't know how this card presents the three bit planes to the mac,

Tangentially interesting part:
IE, does it present the 24 bit pixels "packed" (IE, it fits 4 pixels into three linear 32 bit words of memory space), or does it align them as one pixel per 32 bit word? (It just doesn't have bits to store the extra byte. Modern "24 bit" video systems of course typically use 32 bit memory and can use the extra byte for "other things", like gamma, transparency, z-buffer, whatever.) If it's not packed then your 8-bit mode won't be linear anymore and you'll have to deal with that in software. Quickdraw might not support such a monstrosity.
Folks have been lamenting the inability of some high end cards to output 8 bit for gaming. Might shifting to 32 bit memory be a reasonable explanation for that?

Back on topic: Forgot all about the X/Y pixel limitation aspects for wide screen output for this card!

720x480 AKA 480p, the native resolution of DVD's might be a possible output resolution for this card's hardware?

If so, conversion to HDMI inputs of current 1080p displays and TVs from DVD players are scaled automatically by them. VGA to HDMI converter is an inexpensive little doohickey I've been using with a scaler for oddball Mac resolutions output by proprietary VidCards for SE and such on the TV ext to my hack hutch.

Sticking point here might be flexibility of a VGA converter. Whatcha think, Eudi?


@Gorgonops It's looking like this should be the target resolution? I was worried by not finding 720x480 in the VGA tables.


854 × 480 (FWVGA)​

FWVGA is an abbreviation for Full Wide Video Graphics Array which refers to a display resolution of 854 × 480 pixels. 854 × 480 is approximately the 16:9 aspect ratio of anamorphically "un-squeezed" NTSC DVD widescreen video and considered a "safe" resolution that does not crop any of the image. It is called Full WVGA to distinguish it from other, narrower WVGA resolutions which require cropping 16:9 aspect ratio high-definition video (i.e. it is full width, albeit with considerable reduction in size).

The 854 pixel width is rounded up from 853.3:

480 × 16⁄9 = 7680⁄9 = 8531⁄3.
Since a pixel must be a whole number, rounding up to 854 ensures inclusion of the entire image.[75]

In 2010, mobile phones with FWVGA display resolution started to become more common. A list of mobile phones with FWVGA displays is available. In addition, the Wii U GamePad that comes with the Nintendo Wii U gaming console includes a 6.2-inch FWVGA display.

Such might get through VGA conversion, but half scaled 1080p would be 960x540? Color me a bit confused. :rolleyes:
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