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spaz2
07-09-2002, 02:32 AM
OK... I know this is a done topic but here it is again... On top of it all I thought to putin in "IDE" as G3 ROM is relevent to IDE expansion and support (ie the REV A ROM not supporting M-S)... so... is there a fourth ROM... $77d.45F3?
http://www.zegun.net/g3_rom_dimm_weird.html

trag
07-11-2002, 12:03 AM
spaz2, can you give me some context on where that ROM DIMM was observed? Fascinating.

The chips on that particular ROM DIMM are not ROMs. They are Flash memory chips. Also note that there are four chips with 44 pins each instead of Apple's typical two chips with 70 pins each on a standard G3 ROM DIMM. This is because the Apple ROM is 64 bits wide. The ROM chips that Apple normally uses are 512K X 32 bit ROM chips. Nobody makes a Flash memory chip which is 32 bits wide, so Apple had to use four 16 bit wide Flash memory chips, instead of two 32 bit wide chips.

I would guess that this is one of the elusive flashable ROM DIMMs that Apple uses during in-house development. As such, the actual contents of the DIMM, i.e. the code stored on the chips could be anything. It might be a simple copy of any of the three known ROM revisions or some intermediate version of the ROM code, or some later version which was never released or it could even be blank--erased.

If you have contact with the owner, I would be very interested in getting a copy of the contents of each chip and some additional information.

But to answer your question, there isn't an official fourth ROM revision.

spaz2
07-11-2002, 01:17 AM
hello trag.

i came across this over at the apple bbs/discussion site... the fellow who put up the initial link may be able to point you in th direction you want to go... if you get answers please post it as i am super curious.

It was posted in the Beige G3 section in trhe expansion subsection in the $77D.45F? thread... it is the 33rd post made by "Rick http://macgurus.com/infopop/emoticons/icon_smile.gif" I think.

I've pointed them to your read of the pictures.

[This message has been edited by spaz2 (edited 11 July 2002).]

trag
07-11-2002, 12:57 PM
Thank you, spaz2. I posted to the Apple BBS. Looking at my post here and the one there, I think the one here which I wrote late at night on the fly may actually be more succinct and better written. Sigh. I got a little more detail into the other posting though.

I really want to get my hands on that puppy long enough to extract the contents. The beauty is that the contents are already divided amongst four chips and one experiment I'd like to try is to put the Beige ROM into an x500 series machine. It probably won't work at all, but it depends on how similar the registers in the Hammerhead and Grackle are, and how much legacy code Apple left in when they made the new machines and ROM.

But, you can't just put the Beige ROM in an x500 machine because of the voltage difference of the chips. You could copy the Beige ROM chip contents to 5V chips, but the Beige ROM chips are difficult to copy because they are those oddball 70 pin chips, and even if you could copy them, the contents are formatted for two 32 bit wide chips and the x500 machines need their firmware interleaved across four 16 bit wide chips. This mystery module already has the Biege ROM code broken into four components, so one wouldn't need to mess with trying to extract every other 16 bit chunk and the 44 pin chips are much easier to read than the 70 pin chips.