Can a Rev A 8*24 GC be upgraded to Rev B with a ROM swap?

[olePigeon]

I didn't know there were two different revisions. The Rev B apparently fixes some bugs and adds 832 x 624 resolution and 16-bit color.

Would a ROM swap be able to add the new resolution and 16-bit color? Or would the RAMDAC prevent that from working?

 

[Phipli]

I didn't know there were two different revisions. The Rev B apparently fixes some bugs and adds 832 x 624 resolution and 16-bit color.

Would a ROM swap be able to add the new resolution and 16-bit color? Or would the RAMDAC prevent that from working?

A ROM swap adds the resolution, but not 16bit colour. The 16bit colour mode is a function of the RAMDAC like you say.

 

[bigmessowires]

The 8-24 has a revision B that adds additional supported video resolutions. Is that also true of the 8-24 GC, or might this be a case of confusing two cards with similar names?

 

[Phipli]

The 8-24 has a revision B that adds additional supported video resolutions. Is that also true of the 8-24 GC, or might this be a case of confusing two cards with similar names?

It is also true of the GC. The cards are sister products. Same RAMDAC on the rev As of both types and the GC can bus master the vanilla 8•24 to provide acceleration on that card.

What I am curious about is could you hack a vanilla 8•24 to do 16bit by fitting the RAMDAC used on the Rev B 8•24 GC had doing a bit of ROM hacking (you'd have the GC ROM for reference, but you never know, the programmer might have included support anyway).

 

[olePigeon]

Nuts. That's what I was told, but I had hoped otherwise. I guess I'll have to hold out and hope Siliconinsider can work out the issues with his GWORLD SIMMs not being recognized properly as 4MBs.

 

[Phipli]

Nuts. That's what I was told, but I had hoped otherwise. I guess I'll have to hold out and hope Siliconinsider can work out the issues with his GWORLD SIMMs not being recognized properly as 4MBs.

Shame, but they're pretty awesome cards anyway. I should provide my sources, especially as Apple deleted the knowledge base articles recently.

Here you can see the part numbers for the upgrade kits Apple sold for Rev B ROMs for the 8•24 and for the 8•24 GC, on the Apple website.

Display Card 8■24 & 8■24 GC: Identifying Rev & Upgrade ROM

Here is an Apple note discussing upgrading Rev A cards with a Rev B ROM to gain 832*624, but not 16bit :

Macintosh Display Cards 824 & 824 GC: Rev A/B Differences

Three parts of an other knowledge base article for completeness:

Macintosh Display Cards Overview (1 of 3)

Macintosh Display Cards Overview (2 of 3)

Macintosh Display Cards Overview (3 of 3)

Note it mentions the cards don't work properly in a Mac II with its original ROMs.

One last fact, there is a System 6 and a System 7 driver for the GC, and acceleration starts glitching in the 7.5 era, you start getting artifacts. ReadMe linked.

8•24 GC Drivers attached.

Also the Apple Display 24AC drivers (an unrelated Accelerated Nubus card that Radius made for Apple, sold with some 8100s or stand alone). All this stuff is getting harder to find.

 

[olePigeon]

@Phipli Apparently the reason for its incompatibility with newer systems is covered in the ReadMe file for the Macintosh Drag & Drop extension of all things. It isn't compatible with the 8*24 GC control panel, and will cause visual artifacts as you interact with the screen. HUGE thanks to @jeremywork who pointed this out in another thread, and it was something I never knew about (and would never had known about because I would never had thought to read the ReadMe file for the Drag & Drop extensions.)

So it may just work in 7.5, but you have to make sure to remove the Drag & Drop related extensions. I'm not sure when it was integrated into System 7, as I haven't really used anything past System 7.1.

 

[Phipli]

@Phipli Apparently the reason for its incompatibility with newer systems is covered in the ReadMe file for the Macintosh Drag & Drop extension of all things. It isn't compatible with the 8*24 GC control panel, and will cause visual artifacts as you interact with the screen. HUGE thanks to @jeremywork who pointed this out in another thread, and it was something I never knew about (and would never had known about because I would never had thought to read the ReadMe file for the Drag & Drop extensions.)

So it may just work in 7.5, but you have to make sure to remove the Drag & Drop related extensions. I'm not sure when it was integrated into System 7, as I haven't really used anything past System 7.1.

Interesting, I don't have one so haven't seen the problem first hand.