At 1:41 PM +1000 7/17/00, nigel@ind.tansu.com.au wrote:

>...
>  > Oh, and I should
>>  mention that the LC475 video hack in the NetBSD booter doesn't work
>>  if the machine gestalt is a Q605 (i.e. there's a jumper on J18 on the
>>  motherboard, which I've read changes ROM vectors across the machine
>>  as well as changing the gestalt).  Is this documented anywhere?
>
>	In the Booter Manual:
>
>Video address hack (for LC475 & 575, pre 1.4 kernels)
>    This option should allow the internal video to be used as the
>    console on these two Macs with almost any kernel. These machines
>    use the MMU to remap the video address under MacOS, and this
>    mapping is lost when BSD/Mac68k kernel execution begins.
>    Do not use this option for any machine other than the LC/Performa
>    475, 575 & 630 series, as it may cause undesired kernel crashes

It is jumper J18 on the motherboard of the Q605 and LC475 that 
determines what it is, and I can verify that without the video 
address hack checked in the booter, my LC475 running NetBSD 1.4.2 
does not display the console correctly (I was running 1024x768 @ 1 
bit), and with it checked, the console was fine.  And whether checked 
or not, the Q605 console was messed up, until I removed J18, turning 
the Q605 into an LC475, and then the hack worked.  Here's where I 
found out about J18:

http://www.clas.berkeley.edu/~schrier/q605.html

"The Quadra 605, LC475, P475, and P476 use the same motherboard. A 
jumper in the front left hand corner, J18, differentiates the Quadra 
605 and LC475. The Performa 475 and 476 are the same as the LC475. If 
the jumper is installed, it is a Quadra 605. If the jumper is not, it 
is a LC475. The system and other software know this from what is 
called a gestalt. The gestalt is a number that is specific to each 
type of Mac Apple makes. A Quadra 605 is gestalt 94 while a LC475 is 
gestalt 89."

More on overclocking those machines:

http://www.linkclub.or.jp/~gabezing/LC475-40Mhz-E.shtml
http://socrates.berkeley.edu/~schrier/q605_40.html

>  > If
>>  not, it should be mentioned for folks with Q605 trying to get video
>>  to display properly, or the booter should be updated with another
>>  checkbox and hack.
>
>	I would have thought that, by now, the latest kernels would
>correctly support the video mapping on the LC475 & Q605. The hack
>that I put into the Booter was just a short-term fix for using old
>kernels on the 475/575 machines. I was told that all 1.4 kernels
>already had the correct mapping.

Hmm, I will double check, but I am almost certain that the hack is 
still needed (and J18 needs to be removed on the Q605).

>	I can certainly introduce another hack if someone provides
>me with the correct video address to use, but after 2.5 years I would
>have thought this unnecessary.

I'll let you know for sure soon.  Can anyone else offer experiences 
for or against my observations so far?

--
Nathan Raymond



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