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Wombat (650, 800) board overclocking limitations

lobust

Well-known member
2. My Daystar 128K Quad Cache (aka FastCache Quadra) does not work in the overclocked configuration. The Daystar QuadControl v2.3 init hangs at startup. Unlike the IIci cache card, the Quad Cache card is not enabled until the software kicks in.
2. Sounds about right. I don't know where it is, but there should be an 040 cache thread with info, or Bolle might've chimed in earlier in the thread, but I believe the long and short is that the wait state config on the cache cards is definitely made to work with stock Quadras (not sure about the 840av, since it's a completely different beast), so 33 and below is likely the target.

Apologies for going a bit off-topic, but you two seem to know a bit about the FastCache Quadra and I haven't found much solid information about it before now.

I have one, and installed in my Quadra 800 (modified 650 board, my original 800 board has dead SCSI right now so I can't test it in that one) running 8.1 I can't tell if it's working or not. It gets warm, and the control panel says it's enabled, but tattletech doesn't report anything in the PDS slot, nor does it report any additional L2 cache, and benchmark scores seem unaffected.

The only hint I have seen that it might be doing something, is that it won't enable (greyed out) in the control panel when I have my Silicon Express II card installed as well.

Do you guys know what's up with that? Is there a definitive method to tell if one of these cards is actually enabled or not?
 

jessenator

Well-known member
Apologies for going a bit off-topic, but you two seem to know a bit about the FastCache Quadra and I haven't found much solid information about it before now.
Well, you're giving me far too much credit ;)

I'm sort of along for the ride at this point, really. I made a few "discoveries" here and there, but it was more to fuel my assertion that with a few tweaks and good/late-stage 040 improvement, that overclocks were possible and practical today.

Some conversation was started here:

It might've gotten lost in the crash, but I thought there was a thread solely dedicated to the FastCache Quadra. I don't think all of the PALs got decoded, since one was damaged. I wonder (hopefully not!) if there's a fault in one of the same PALs on your cache card.

Apple's and oranges here, but there's documented evidence on the Micron Xceed card of regular failure on specific RAM ICs. This is complete supposition, but it might be a similar thing where the chip fails in the same way on the same device. Again, hopefully not with yours!

I think it's the perfect idea for a new thread, though! Might bring out the real experts that way :)

Is there a definitive method to tell if one of these cards is actually enabled or not?

Wild guess here, but I think either MacBench 4 or TechTool Pro will give an accurate-ish readout. It's far more accurate than Apple System Profiler. MB4 will actually detect and accurately tell me what my PPC's L2 cache is, while ASP just says "256k" regardless…
 

trag

Well-known member
Cacheometer (cachometer?) from NewerTech will usually report accurately if a cache is present adn working. Sometimes easier to find in the "guages" collection.
 

David Cook

Well-known member
Cacheometer (cachometer?) from NewerTech will usually report accurately if a cache is present adn working. Sometimes easier to find in the "guages" collection.

I found Newer Technology Cache-22 v1.2.1, v1.41, and v1.5.1 on the Macintosh Repository. All indicate they need a PowerPC processor to run. I'd be interested if anyone has a different experience or version that runs on the 680x0 series.
 

trag

Well-known member
I may have been mistaken in suggesting them. Memories are old and vague. There probably wasn't any reason for NewerTechnology's utilities to support anything before the PPC machines.

Sorry.
 

David Cook

Well-known member
Here's some fun for your Saturday night. I wrote a quick little program that allocates a memory block and reads it repeatedly for 1 second. It then repeats that for various memory block sizes. Theoretically, it should show hints at the sizes of various caches.

There are four tests plotted (two runs each of no cache and 128KB cache), but only two are obvious because the test results show strong repeatability. To simplify, the red line is 'no cache' and the orange line is '128K cache'.

1657422380233.png

Here you see that performance starts to drop off around 4 KB. That's the internal L1 68040 cache. There is the start of a drop between 2 KB and 4 KB, but that's because the CPU is using some of the cache for other purposes and can't fit my entire 4 KB memory chunk.

The orange line shows a moderate drop starting at 4 KB, but that's because the 128 KB cache is at level 2 (L2) so is not quite as fast as the internal CPU cache. After 128KB we see a significant drop.

Surprise: The 128 KB cache causes further memory accesses to be SLOWER than without the cache. This is the cost of a cache miss (or memory controller timing change?). Bummer!

The difference between the slope of the CPU cache miss (curved) and the 128 KB cache miss (hard drop) suggests Motorola had a better caching algorithm.
 
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David Cook

Well-known member
Now let's look at the Macintosh IIci.

1657423015686.png

The peak at 256 bytes is because the 68030 has a 256 byte L1 data cache!

The drift upward of the red/blue and green/light blue lines is an artifact of the code. Basically, the overhead of the loop code itself slows down the total number of bytes it can read per second for smaller block sizes.

The yellow/grey line shows a drop after 32KB, owing to the 32 KB L2 cache card.

The green/light blue lines drop after 128KB, showing that the 128 KB L2 cache card is working.

Surprise: The Micron 128KB cache card is slightly more effective at reads outside the cache range than the Apple 32KB cache card. Cache algorithm? Memory controller timing?
 
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