bart@reed.UUCP (Bart Massey) (09/05/88)
I've tried and tried to figure this out with no real success, and I desperately need the info, so you good net folks have become the last resort for this query: The Addison-Wesley version of "Designing Cards and Drivers For Macintosh II and Macintosh SE" is (somewhat inexplicably) the only source of hardware info I've found for Apple's Mac II video card. In the chapter entitled "The Macintosh II Video Card", it describes 20 "parameters" which control Frame Buffer Controller video generation on this card. We are told that the Frame Buffer controller has a set of 16 8-bit registers which contain these parameters, that the registers are mapped into the Video Card slot memory, that is a bad thing to ever use these registers (so why do they describe them in so much detail?). What we AREN'T ever told is how the parameters map onto the registers, and how to alter the registers! I've also tried all the IM volumes, all the other Addison Wesley booklets, the Tech Notes, and even AppleLink to tech support, with no success. Presumably if one knows the magic mapping and the magic address, one can just blort into video card memory the appropriate values... There might be a better (i.e. "cleaner", more compatible) way to do this, though -- I don't know. I actually have the magic address, courtesy of the "Interlace" INIT posted to the net a while back. I wrote the author of this INIT for info, but received no response... The reason I'm so curious about this, in case you're interested, is that I am currently driving my home Mac II with a whacked Tektronix 4107 monitor I got surplus for $70. It happens to be a 31.25 KHz monitor, but I am semi-successfully driving it with the Mac II's 35 KHz output, by tweaking the horizontal sync pot in the monitor about as far as it will go. This is clearly bad. Equally bad, I have a much nicer Tek 4109 monitor sitting in my garage waiting to be hooked up, but it doesn't happen to be able to sync on a signal which is 12% too fast. What I propose to do is write a CDEV/Init pair which lets one customize the Mac II video card for odd monitors. This seems to me like a great way to save myself and other hard-core HW/SW hackers many $$$. But to do it, I desperately need the above-requested info. Thanks for any info you might have! I will most certainly summarize to the net (unless Apple is the only source of help and asks me not to :-)! Bart Massey UUCP: ..tektronix!reed!bart