PM 8600 Rev A & Rev B Logic Boards

[aplmak]

So I purchased a Rev B logic board as a backup. Since it was a Rev B I figured I’d swap it out. Now I recapped it with quality SMD Tantalums before doing this. And it will not fully boot. It powers on and drives spin up and such but no boot chime. I’ve rechecked all the caps and values as well as proper soldering work. They were not leaking but I have a habit of storing machines for years and wanted to get ahead of future leakage and put quality non leaking Tantalums in. I should have tested it before. Is the Rev B compatible with the 8600/300? This Rev B is from an 8600/200. I noticed there is a cache slot on Rev B compared to built in on Rev A. Anyone have any ideas on what I should try??

 

[David Cook]

My 8600 Enhanced logic board is 820-0931-A. I believe the unenhanced board is 820-0858

According to the Apple Enhanced Power Macintosh 8600 and 9600 Computers developer note, page 3:

The control logic on the main logic board has been changed to support the inline cache on the processor card. The new processor card will not work in an older model Power Macintosh 8600 or 9600

They changed the ROMs to support the new processor cards.

 

[DarthNvader]

Is the Rev B compatible with the 8600/300? This Rev B is from an 8600/200. I noticed there is a cache slot on Rev B compared to built in on Rev A. Anyone have any ideas on what I should try??

No the Mach 5 CPU from a Kanas board will not work in a Nitro architecture logic board.

The Mach 5 CPU has 1MB inline L2 cache running @ 100mHz on the CPU daughter card. As you have said the Nitro architecture 8600/200 had the L2 cache on the logic board.

 

[aplmak]

Ok thanks for the info! I was not aware of the difference between the logic boards.. it was basically the same board just different revisions.. so I thought it would just add more backside cache that’s all.. but as you said the will not work with the newer processor with built in cache.

 

[trag]

The 8600 board, non-Mach 5 CPUs, and the 8600 Enhanced (AKA Kansas), Mach 5 CPUs (and upgrades) only, can be distinguished in three ways.

The Enhanced (Kansas) board should lack the Cache slot. It will have a position for the cache socket but it won't be installed.

ROM chips are four 1.1" X .5" chips with 44 pins (22 on each long edge) and are located on the back (underside) of the logic board.

The original 8600 has ROM chips numbered (labeled) 341S0280 - 341S0283, which delivers $77D.34F2 as the Firmware Revision in Apple System Profiler. If you happen to have an 8500 board then it's 341S0169 - 341S0172 and $77D.28F2. Other than the ROM revision and the power supply connector there's not really and difference between an 8500 and original 8600 board, as far as I know.

The 8600 enhanced has ROMs which are updated to $77D.34F5 with chips labeled 341S0380 - 341S0383.

 

[aplmak]

Interesting Trag.. I’ve got (3) 8600 boards I’m gonna check out the ROMS on now and see what I’ve got. On both revisions capacitor spot C43 looks like Apple never put a cap there.. I accidentally put one there.. I removed it and it’s fine now. Very odd.. I’ve never seen a cap spot with no cap on an Apple board before.. even flowed with solder..

Looking at one now I’ve got ROMS 341S0381, 383, 382, 380

 

[David Cook]

Using a multimeter, you can determine that the positive terminal of C43 connects to fuse F1, which in turn connects to pin 1 of the AAUI port. The negative terminal of C43 connects to the ground plane.

C43 is just a bulk capacitor to provide a nice steady supply to the AAUI adapter. There should be no harm in populating that. The bulk capacitor is good practice, but not necessary.

 

[aplmak]

Gotcha.. I wonder why they were so cheap not to populate it

 

[trag]

Looking at one now I’ve got ROMS 341S0381, 383, 382, 380

So that's a Kansas, AKA 8600 Enhanced.