Mac OS 9 Lives! (Classic Mac OS Forum)

Classic Mac Hardware (Troubleshooting, Upgrading, & Modifying) => General Hardware Discussions => Topic started by: FBz on September 16, 2021, 01:13:59 PM

Title: 150 MHz QS Bus Speed!
Post by: FBz on September 16, 2021, 01:13:59 PM
Overclocking Apple Quicksilver System Bus to 150 MHz?

Searching for instructions on overclocking the MDD 1.25 GHz & 1.42 GHz CPU’s
stumbled upon MacTron’s post,2903.msg18351.html#msg18351
Mentions increasing Quicksilvers’ bus speed to 150 MHz & found this bit of how-to instruction.

Might give this a whirl.
Seems easy enough and reportedly… with little resultant heat increase?
I’ve plenty of QS “A” MOBOs to test this on before same on “B” board.

Although I do wonder about this:
“Also take note that OSX will not recognize in these analyzes,
the overclock of the bus to 150MHz nor the real frequency of your processor.
Regardless, the important thing is that it works!”

Anyone here attempted this, in this manner / fashion?
Title: Re: 150 MHz QS Bus Speed!
Post by: FBz on September 21, 2021, 04:05:30 PM
150 MHz System Bus hack on a Quicksilver 820-1276 “A” board. Used a 22Ω .25W resistor and a soldered in-place jumper. Used same RAM and nVidia from Quicksilver that had a bootable “B board” to start… with a solo Inland 128 GB SSD (via a trusty RXD-629A7-7 bridge adapter) and only 1 GB RAM installed. QS 867 MHz CPU.

No massive differences noted with QuickBench 2.0  - but maybe QB isn’t the best method to measure the touted 12% System Bus speed increase against original config. It seems faster. [QuickBench results from the original are top results, over the results from the hack (bottom).] Click attachments.

Original 22Ω resistor appears different - but the newer resistor has same values.

Example per instructions:

Step 1:


Unable to source a 1 GHz DP for the QS but did get a 933 and I thought this hack might help it a bit towards that 1 GHz performance goal. Next I’ll do same hack on Quicksilver “B board” max the RAM and install that 933 CPU.
Title: Re: 150 MHz QS Bus Speed!
Post by: DieHard on September 21, 2021, 04:55:28 PM
Wow, this is so nicely posted... you get another "DieHard Santa" package this year !

I will try to include small items this time as the ADC monitors provide further "clutter" to your lab :(

Oh, and let me know if you need a few dozen more "Bribge" SATA to ATA adapters 'cause I am starting to run out of experiments with them
Title: Re: 150 MHz QS Bus Speed!
Post by: Bolkonskij on September 22, 2021, 11:58:54 PM
I never cease to be amazed at what folks are still able to achieve on our older Macs - well done, FBz! Does it run stable?
Title: Re: 150 MHz QS Bus Speed!
Post by: FBz on September 25, 2021, 09:49:45 AM
Thanks Bolkonskij und Diehard
(aka: Lemmy). ;)

Again however, credit where credit is due goes to Jonathan Renaud.
I just followed his instructions from a post back from around 2007(?).

Yes, it’s been running stable since the hack. Haven’t done the “B board”
with that 933MHz CPU yet but it’s on my list. (Been a bit preoccupied
with a “white whale”.) Still thinking that if possible on a QS, maybe
something similar on an MDD… to improve DTR with SSDs?

And as far as “clutter” goes here…
How can you “see” when I’ve taped over the camera on this iMac? :o
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