Classic Mac Hardware (Troubleshooting, Upgrading, & Modifying) > Mac CPU Upgrades

1.42 GHz MDD CPU to 867 MHz MDD / swap

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FBz:


Prompted by OS923’s recent 1.42 CPU swap to a lesser MDD
… so of course mine, would be different.  The 867 MHz DP
has a 133 MHz bus speed, as opposed to the 167 MHz of the
later MDDs. (Except for DP 1 GHz FW800 MDDs /which also
had / has a 133 MHz bus?)

Mine, from last night:


Now I’ve seen the thread by ProtoolsLE5Guy & MacTron
http://macos9lives.com/smforum/index.php?topic=1652.0
-which is very informative but it still remains fairly unclear.
There’s another old thread over on MacRumors.com that
deals with the same matter and it suggests the removal
of a single solitary resistor (R676) on mobo’s backside
to enable bus speed change from 133 Mhz to 167 MHz.

https://forums.macrumors.com/threads/guide-to-changing-mdd-bus-speed-cpu-upgrade.1708627/

So before I remove the mobo and the (R676) resistor…
anyone have any actual insight into this little escapade?

Sure it would’ve likely been easier to trade a 1.42 CPU
with a 1.25 DP CPU MDD - but first, the 867 MHz MDD
might benefit more. (Especially if only requires removal
of a single resistor.) Changing the bus speed should do
the trick, without changing anything on the 1.42 CPU?

(The 1.42 GHz CPU into 1.25 DP MDD swap will be next.)

Here’s a 1.42 GHz FW800 mobo close-up and you may
note the absence of the R676? Which = 167 MHz FSB?

Protools5LEGuy:

--- Quote from: FBz on April 18, 2022, 03:11:58 PM ---

Now I’ve seen the thread by ProtoolsLE5Guy & MacTron
http://macos9lives.com/smforum/index.php?topic=1652.0
-which is very informative but it still remains fairly unclear.
There’s another old thread over on MacRumors.com that
deals with the same matter and it suggests the removal
of a single solitary resistor (R676) on mobo’s backside
to enable bus speed change from 133 Mhz to 167 MHz.


--- End quote ---

Consider yourself lucky. You didnt had to deal with the MacBidoule article in a time when Google translate just didnt  do a thing right(excuse french folks if I mispelled)

Certainly the post is long (2014 started) but I think I almost killed it in 2020 with the HD pictures of the green and the blue boards.

Long read... yes I have to admit. Fairly unclear? Strongly disagree.

Read it twice and excuse the offtopic around.

Dont feel bad for re-reading. I have read 15 times opencore legacy patcher wiki and still havent a clue.  :)

Protools5LEGuy:

--- Quote from: FBz on April 18, 2022, 03:11:58 PM ---Changing the bus speed should do
the trick, without changing anything on the 1.42 CPU?


--- End quote ---

Yes. But when you read the macbidoulle article translates as the opposite.

Also it didnt helped that the representation of the resistors in some schemes are "X" marked.


--- Quote from: FBz on April 18, 2022, 03:11:58 PM ---

Here’s a 1.42 GHz FW800 mobo close-up and you may
note the absence of the R676? Which = 167 MHz FSB?


--- End quote ---

Yes

Protools5LEGuy:
Also is a bit unclear on the "overclock 866 dual daughtercard" vs "unlock 166 bus on 133 motherboards". Those are 2 subject.

2 resistors vs 1 resistor.

One on the backside of the motherboard + One on the CPU daughter card Vs Only the one on the backside 

FBz:
Well, it worked! Simple.
Removed only the R676 resistor from the DP 867 Mhz mobo
and effectively changed the FSB from 133 MHz to 167 Mhz.
(Apple 820-1445-A mobo)



But, not at first.
After removal and reassembly it wouldn’t boot.
So then re-soldered the resistor back. Still no boot.
Placed PSU & CPU back into 1.42 GHz FW800 MDD.

Still no boot. >:(
(Samsung PSU had failed!)

All over again this morning. Removed R676.
Then re-installed mobo along with CPU & new PSU.
BOOT!!!



I’ve more FW800 machines than FW400 - and prefer the latter.
This 867 MHz DP machine is a welcome addition…
with a 1.42. GHz DP and a copper heatsink.

Results from an Inland 128 GB SSD w/ Bribge adapter:



Thanks Protools5LEGuy! ;)

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