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    7451 to 7455 iMac G4 CPU swap attempt (WIP)

    Thanks for sharing your experience. The OEM chips typically used a 0.89mm Diameter 90% Pb and 10% Sn (by Weight) “High Melt” solder ball held between CBGA substrate and PCB with regular eutectic (63Sn/37Pb) solder. The idea was to have a ball that would not collapse when attached. The...
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    Power Mac G4 Gigabit PSU repair, no power

    I have repaired several of them, by replacing capacitors. The fans can usually benefit from some attention as well.
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    Experiments with G4 external/backside cache

    The later G4 chips had the L2 cache built in, and the external cache (where available) becomes L3. With this series of chips there is also now the option for DDR SRAM chips, vs the earlier SDR versions. So this is looking at the "7450" G4 chips with different cache configurations, using the...
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    Power Mac G4 MDD No Video

    What went wrong with the original CPU? A common way to troubleshoot is to swap parts with another machine to narrow down the possible problems. Just based on your description, I would guess the problem is CPU related. There were several versions of the MDD, possible CPUs, heatsinks, etc...
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    How did the PowerPC 603 / 5200 at 75mhz compare to PC:s (486/Pentium)?

    At the same clock I would estimate it at around 5x faster than the 486 and around 50% faster than the pent. This CPU benchmark has been run on a lot of different hardware over the years, and is one way to try and compare different machines using the same software...
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    Experiments with G4 external/backside cache

    More data points to better see what's going on, and both views on the same plot:
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    G4 cube an Sonnet Encore ST Duet G4

    Speed/voltage are configured with resistors on the Sonnet PCB. 68kmla.org/bb/index.php?threads/overclocking-the-sonnet-encore-st-g4.38487/
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    G4 cube an Sonnet Encore ST Duet G4

    Is this the same Cube that wouldn't work with the Sonnet "1.2"? What was the problem there? Without much to go on, I would guess it's a power supply problem. What are the voltages at the CPU? Does the Dual work in a different machine? Does the Cube work with a different CPU? You could...
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    Saving a 3400c logic board

    Going by your pictures, that's a test pad. There was never a component connected to it.
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    Interest in adapting 744x to 7400?

    I have put 7447/7448 chips onto a variety of other boards, but the 7450 adapter is something different. The only 7450 type CPU boards that will easily fit a Cube are aftermarket already.
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    Interest in adapting 744x to 7400?

    The extra cache seems to have a bigger benefit on the slower bus in the Cube:
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    Interest in adapting 744x to 7400?

    Someone sent me some 7448 chips to install, and I can report that they also work fine on these boards with the 7400 adapters. The Powerlogix/Newer Technology patch works to fix the firmware on machines that use these boards.
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    iMac G3 (Rev A -> C) G4 CPU Upgrade

    Thanks for sharing your results! I was tinkering a bit with a 7410 in a Pismo and tried it at 1.6v and 500MHz. It was happy with these settings and cool running. I also tried 1.5v, but that was too low for stable operation once it got warm. So one more data point... ymmv.
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    Pismo (G4) Firewire weirdness?

    Does the external drive have its own power, or are you powering it through the Pismo?
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    Pismo (G4) Firewire weirdness?

    What firmware version does your Pismo have?
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    Experiments with G4 external/backside cache

    I added data for the 256KB setting. This plot also shows another way to look at the same data. With zero L2 cache as the baseline, this shows the speed increase with different amounts of cache added. So it's like looking at the performance hit for not having the cache, or the performance gain...
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    Experiments with G4 external/backside cache

    This shows testing with sorting arrays of integers. The size of the arrays increase: 16KB, 32KB, 320KB, 3.2MB, 32MB, and 64MB. The plot shows sorting speed relative to results with 2MB of L2 cache. You can see that less cache is always slower, but there is a range of array sizes where the...
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    Experiments with G4 external/backside cache

    On the G4 CPU, the external memory cache is configured with a register. In the following example a 600MHz 7400 CPU has an actual 2MB of L2 "backside" cache physically existing in hardware, but reduced amounts of 1MB, 512K, and zero L2 cache can also be set in software. This picture is showing...
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    550MHz G4 PowerBook (Pismo vs Titanium)

    I think some of the reported L3 issues are firmware or power-saving related. Maybe some of the firmware experts could figure out the details of what it's doing, but I think the later Titaniums would turn off L3 when on battery, or when in "reduced" performance mode. The CPU speed and voltage...
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    BeBox lives after 2+ years!

    That's neat! --thanks for sharing. It's kinda like hooking up the LEDs on a RAID card and watching them all go.