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mectojic

macrumors 65816
Original poster
Dec 27, 2020
1,354
2,560
Sydney, Australia
I've got a Sawtooth 400MHz G4 with 2GB ram. Haven't touched the original ATI Rage Pro 128 graphics card (16mb Vram).

Can this Mac handle a modern 1080p monitor via VGA output, or do I need to upgrade the video card?

i.e. I don't know anything about vram/pixel correlation, or whether VGA/DVI connection makes a difference.
 
Not an expert on the subject, but wanted to say that VRAM is simple to calculate. A single buffer worth of screen at 24-bit color is 24 bits aka 3 bytes per pixel. Formula:

3 * 1920 * 1080 = 6220800

So you need 6220800 bytes.

6220800 / 1024 / 1024 = 5,93

That is 5,93 megabytes. Sounds like 16 megabytes is enough for double buffer, even. If the Rage could do some hardware OpenGL, there will be very little memory left for that.

Also, 1920*1080 can be done over both VGA and DVI. With VGA you want a good-quality display cable.
 
I've got a Sawtooth 400MHz G4 with 2GB ram. Haven't touched the original ATI Rage Pro 128 graphics card (16mb Vram).

Can this Mac handle a modern 1080p monitor via VGA output, or do I need to upgrade the video card?

i.e. I don't know anything about vram/pixel correlation, or whether VGA/DVI connection makes a difference.
According to Everymac yes:

 
Can this Mac handle a modern 1080p monitor via VGA output, or do I need to upgrade the video card?
Yes, but only via VGA. I have run 1920×1200 via VGA from my Pismo's 8 MB Rage Mobility 128, so the G4's 16 MB Rage 128 Pro should also handle it.

Also, 1920*1080 can be done over both VGA and DVI. With VGA you want a good-quality display cable.
Theoretically, yes. The problem is that the Rage 128 Pro's TMDS transmitter (the thing that drives the DVI port) cannot push the pixel clock necessary for 1920×1080 at 60 Hz, which is 148.5 MHz when using HDMI timings or 138.5 MHz when using CVT-RB timings. It can push 112.27 MHz which is what the 22" Cinema Display requires for 1600×1024 at 60 Hz, and the Rage 128 Pro was the card that went along with it.

The VGA port can handle higher pixel clocks because CRTs require a much larger/longer blanking period than LCDs, increasing the pixel clock necessary for a given resolution-and-refresh-rate combination. For instance, 1920×1080 at 60 Hz requires 173 MHz when using CVT timings suitable for CRTs.
 
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The VGA port can handle higher pixel clocks because CRTs require a much larger/longer blanking period than LCDs, increasing the pixel clock necessary for a given resolution-and-refresh-rate combination. For instance, 1920×1080 at 60 Hz requires 173 MHz when using CVT timings suitable for CRTs.
Are you implying that the CRT support within VGA accidentally helped to support higher resolutions on LCDs due to the refresh rate being higher on CRT? That’s cool.

It’s great to hear 1080p will work- Sawtooth G4 is about as early in tech as I’m willing to go, whilst 1080p monitors are the newest tech I need- I personally never cared for retina or 4K. So this sounds like a wonderful match!
 
Are you implying that the CRT support within VGA accidentally helped to support higher resolutions on LCDs due to the refresh rate being higher on CRT? That’s cool.
Only for LCDs connected via VGA.
The maximum pixel clock attainable via VGA is determined by the RAMDAC. If you're "lucky" it's 400 MHz (or even higher).
A 400 MHz pixel clock is enough for e.g. 2304×1440 at 80 Hz using CVT timings... for, say, the Sony GDM-FW900 mega-CRT.
Or 2560×1600 at 88 Hz using CVT-RB timings... but good luck finding a 30" LCD with a VGA input that accepts this mode :)

The pixel clock limit for digital TMDS connections (e.g. P&D, DFP, DVI, HDMI) is determined by the TMDS transmitters, and early ones topped out at much less than the actual 165 MHz limit single-link DVI connections are subject to:
The first generation of TMDS transmitters topped out at 86 MHz pixel clock.
The second generation, as well as those built into some early DVI-compatible GPUs (such as the Rage 128 Pro) topped out at or around 112 MHz.
 
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Yep. A “LED monitor” is an LCD monitor which uses a LED backlight as opposed to one or more CCFL lamps.

@mectojic I use an LED TV with several of my PPC Macs via its VGA port and I can select from a wide variety of resolutions. Obtaining a consistent image via HDMI is problematic due to issues with the pixel clock which @Amethyst1 mentioned earlier.
 
Never realised how useful VGA could be. That’s awesome.

Definitely and that LED TV is a godsend because annoyingly, my expensive main TV lacks a VGA port. The former was stumbled across one night in my neighbourhood having been dumped by someone. It has VGA, 2x HDMI, Component Video (YPbPr), Composite Video and SCART (Euroconnector). It also has a DVD drive, a DVB-T tuner, is compatible with PAL and NTSC and works with every voltage from 100 to 240.

At 22" it can be carried very easily and the next time I travel abroad I'll take it with me so that I can watch local broadcasts free from the conflicts that ensue when only one TV is available in a household and it's shared by half a dozen people. :D
 
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