68 PIN VRAM Spec

[Aoresteen]

Does anyone have the Apple 68 pin VRAM pinout specs for a Qudra 605, 700 etc? How many memory address lines are there? They came in 256K & 521K sizes.

Since the largest size VRAM that I've seen is 512K that implies 19 adress lines but I was wondering if the 20th line was there, allowing 1 MB VRAM SIMMS *in theory*. I doubt that the Q605 MOBO would reconize it but was curious about the number of address line.

Also, how do you tell if the VRAM SIMM is 100NS or 80ns?

Thanks!

 

[Trash80toHP_Mini]

It's in the DevNote Block Diagram:

Connection between ASIC MEMCjr & VRAM is VA0-8 = 9 address bits (lines?) = 512k VRAM max as I read it, SIMM select would be the wild card.

Check the DevNotes to see if any other Mac with MEMCjr on board addresses four VRAM SIMMs. That's doubtful, few (any at all?) video subsystems supported 24bit Color at anything over 16" Resolution, which would require 3MB of VRAM. So I doubt MEMCjr would have that capability.

The first Mac to have VRAM SIMMs may have the full spec & pinout, but my guess it's in DC&DftMF.

 

[dougg3]

I checked some of the devnotes and couldn't find the pinout in any of the relevant models -- Quadra 700, Centris/Quadra 610/650/800, LC 475/Quadra 605.

It looks like Macs as early as the LC had the socket, and unfortunately the LC's devnote seems to be impossible to find. I'd wager a guess that the pinout is in the LC devnote. The LC is too new to be in Guide to the Macintosh Family Hardware. It's in Apple's list at the link above, but the link unfortunately points to the LC 475 note instead. If anyone ever finds the original LC dev note, I'd be very interested in adding it to my collection!

 

[Trash80toHP_Mini]

I've looked at DC&DftMF, the LCIII and LCII (all 18 pages of it 8-o ) DevNotes and come up with absolutamente nada.

I couldn't find the LC DevNote either! Was there ever a .pdf DevNote for the LC?

 

[LCGuy]

According to the LC II devnote, there was. No idea where it can be found though. :-/

 

[Trash80toHP_Mini]

There's a kind of no-man's land between the books and the DevNotes in Apple's documentation. I wonder if the LC DevNote pre-dates Developer CDs? :lol:

 

[Trash80toHP_Mini]

Found this . . .

http://support.apple.com/kb/TA46422?viewlocale=en_US

. . . but searching "Macintosh LC Computer Developer Note" didn't turn up anything much so far.

This is worse than Where is Waldo? :