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1920x1080 on PM8500 built-in, Twin Turbo 128

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#1 noidentity

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Posted 03 November 2009 - 11:17 AM

I have been able to hack the built-in video driver of my PowerMac 8500 to support 1920x1080 and 1680x1050 LCD panels perfectly (been using 1920x1080 for over a month now with zero problems). The LCD is able to lock on to the pixel rate and phase so that each pixel is perfectly clear, no blurring or anything. The new resolution shows up normally in Monitors, and when selected and the machine restarted, it will properly switch to the new resolution part way through the boot screen.

I've also done the same for the IX-Micro PCI video card that the PowerMac 9600 and some others used. This will probably also work on all PowerMac models using the same video circuitry: 7300, 7500, 7600, 8500, and 8600 (maybe someone can post a definitive list of models using the same circuitry, in case I left some out). This is a software-only modification; no hardware changes needed.

Is there any interest in posting these, or does everyone use these older machines on smaller displays or with newer video cards? I've figured out how to adjust all the standard video parameters, allowing custom modes with other resolutions too. The parameters adjustable are pixel rate (e.g. 148.5 MHz), horizontal rate, refresh rate, front/back porch and sync width for horizontal and vertical, and of course the horizontal and vertical pixel size. There are no code changes, just adjustments of the timing values in the driver. There is also a choice of modifying the driver in the System file, or modifying a video driver extension. Also, adjustments can be made to parameters without restarting.

#2 mac2geezer

  • 6502
  • LocationOregon

Posted 03 November 2009 - 04:49 PM

Please do post your goodies. I'm not currently using any monitor larger than 17 inches on the 8600 but who knows what might happen in the future.
IIfx 80MB 1.2GB HD, slot load G3 iMAC, 20 in C2D iMAC, 8600/300, 9600/300 w G4/800, 2.3GHz DC G5, 2.5GHz Quad G5, Powerbook G4

#3 beachycove

  • 68020
  • LocationOntario

Posted 03 November 2009 - 07:15 PM

This is marvellous stuff. Under what System/s will it work?

#4 Charlieman

  • 68000
  • LocationLeicester, UK

Posted 03 November 2009 - 07:57 PM

Excellent work, Noidentity. I suspect that you are repeating some of the investigations performed by the authors of the various shareware "set res" utilities, but it is much better to have this info in the public domain. If you need a host for a couple of web pages, pm me (but don't expect a reply for a bit).

My stuff is at http://www.vintagemacworld.com/ BTW.

#5 noidentity

  • 6502

Posted 03 November 2009 - 08:03 PM

I'm using Mac OS 9.2.2, but I imagine it'll work even with System 7 (I could try tomorrow, as I still have an easily-bootable version of it... I didn't stop using System 7 until about 2004!). Like I said, it's just modification of the video mode parameters in that special video driver that works with System 7-9. And yeah, it goes way beyond any of the resolution drivers I've seen before, basically what Switch Res X supports on OS X. I could also add resolutions for 1440x900, 1600x1200, etc. The first thing is to have others try it on their displays. Anyone actually using one of the mentioned PowerMac machines with a widescreen or fairly large LCD?

#6 noidentity

  • 6502

Posted 05 November 2009 - 05:23 PM

This program and driver allow custom resolutions using built-in video on a PowerMac 7300, 7500, 7600, 8500, and 8600. I have used it to get perfect 1920x1080 on an LCD for over a month now. I have tested it in Mac OS 9.2.2 and Mac OS 7.6.1.

* To use, you first need a "modeline" or the raw video parameters your display uses. When using a modeline, you can paste the full modeline, or strip off the ModeLine "123x456" prefix and also the sync polarities from the end. For example, you can paste

148.35 1920 2008 2052 2200 1080 1084 1089 1125

into the modeline field without problem.

* Put the "73/75/76/85/8600 GraphicsDriver" extension into the Extensions folder, but don't restart yet.

* Run Customize and paste your modeline into the Modeline field and click Decode, or enter the individual parameters into the fields.

* Click Save, then restart.

* Open Customize again and click Apply. This will try the new resolution until you click the mouse. If it doesn't work, you can adjust parameters and click Apply again until you get them right.

* Once you have good parameters, click Save, then open the Monitors control panel and select the new resolution and enjoy (on System 7, hold the Option key when clicking Options... in the Monitors control panel, otherwise the custom resolution won't show up).

The refresh rate, horizontal rate, and pixel clock fields all control the same thing, so only one really matters. If you want to specify a particular one and have the others derive from it, clear the other two.

This driver is based on the original "73/75/76/85/8600 GraphicsDriver". All I've done is decompress the globals in the extension to make them easy to modify, and written the Customize application to modify the parameters. The driver code is unchanged.

Here are a few modelines I've used:

ModeLine "1680x1050" 147.14 1680 1784 1968 2256 1050 1051 1054 1087 +HSync +VSync
ModeLine "1920x1080" 148.35 1920 2008 2052 2200 1080 1084 1089 1125 +HSync +VSync

Download it here: CustomGraphicsDriver.sit

#7 ccmac

  • 6502

Posted 28 November 2009 - 04:32 PM

How do you obtain the "modeline" for any given monitor?

#8 noidentity

  • 6502

Posted 28 November 2009 - 07:40 PM

I'd google for them. The MythTV Modeline database might have what you need. Another place for the raw values is the EIDE info for the display, which you might also find on the web. Any particular resolution you're trying to achieve?

#9 ccmac

  • 6502

Posted 30 November 2009 - 04:29 PM

I don't really use my 8500 that much anymore. However, I downloaded your utility just in case I need it in the future and I wanted to make sure the documentation is as complete as possible. Thanks for the added info.

#10 mainframemike

  • 6502

Posted 15 December 2009 - 12:40 AM


This worked great on my 8600 built-in video. Can you post the version for the 9600? I have a Twin-Turbo 128 M8A that I think is the same as the 9600 PCI card.


#11 noidentity

  • 6502

Posted 15 December 2009 - 02:50 AM

Thanks for confirming that it works for someone besides me! What resolution are you running the 8600 at with it?

I'll have to do some coding before I can post the TwinTurbo version using that latest GUI. I pulled my card out and it is the TwinTurbo 128M8A version 3.8.1 (looking at the tag on the EPROM). What resolution are you intending on running this one at?

#12 mainframemike

  • 6502

Posted 15 December 2009 - 08:29 PM

I am running 1680x1050 on a ViewSonic VG2230wm, and intend to use this with the TwinTurbo 128M8A also. I prefer to use the TwinTurbo as it seems slightly faster and has more VRAM. I have a 1920x1200 display, and can try it with that if you would like the test results. This is attached to a different computer. It is really nice not having the stretched screen I have been putting up with since my CRT died.

I used your timings, and they seem pretty good so I did not spend any time tweaking the modeline. The one in the MythTV database was no good.


#13 noidentity

  • 6502

Posted 16 December 2009 - 03:40 AM

OK, here's the TwinTurbo 128 M8A version: Custom_TwinTurbo9600_Driver.sit

I included extensions pre-configured for 1680x1050 and 1920x1080, so for those resolutions, just drop the appropriate extension and restart, then select the resolution in Monitors. Currently I haven't figured out how to have it re-select this resolution each time you restart (it'll show it selected for me, but I have to switch to another resolution, then switch back, to get it to take effect after a restart). Let me know how this works on your TwinTurbo.

Here's the same for the built-in version, extensions pre-configured for 1680x1050 and 1920x1080 (no other changes to this): CustomGraphicsDriver.sit

#14 ClassicHasClass

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  • LocationElectron Alley

Posted 16 December 2009 - 06:11 AM

Outstanding work. I just got my first 1080p display this weekend, so I might drag the 7300 bedroom system into the workroom and try your driver at 1920x1080.

#15 mainframemike

  • 6502

Posted 17 December 2009 - 05:00 AM

home.ripway.com is timing out when I try to download the driver. I will try again tomorrow.


#16 mainframemike

  • 6502

Posted 17 December 2009 - 09:25 PM


I was able to download the driver today. It is working great on my TT128 at 1680x1050.

Thanks again,

#17 olePigeon

  • 68LC040

Posted 29 December 2009 - 04:53 PM

If you have a 3dfx VooDoo 3, 4, or 5 video card, the resolutions available for the OS are contained in a simple text file that you can modify. I thought it was pretty nifty, you could do any resolution you want to with it.

#18 beachycove

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  • LocationOntario

Posted 29 December 2009 - 09:37 PM

What/ where is the text file for the Voodoo cards? I have a Voodoo 5 that one of these days will run an LCD; it'd be handy to have the details squirreled away for that purpose.

#19 noidentity

  • 6502

Posted 31 October 2010 - 03:46 PM

Updated links to drivers (still working great after a year on my PM8500 with built-in video on a 1920x1080 LCD):



#20 LC_575

  • 6502

Posted 17 November 2010 - 09:57 PM

Is there any way I might get this to work on my Performa 6300 using the built in video?
Lost all the Macs to Hurricane Sandy.

The '90's didn't end with New Year's 2000. They ended with the release of 9.2.2.

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