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Daystar Universal PowerCache P33 in SE/30

Bolle said:
Connect /CENABLE (pin C13 on the PowerCache slot on the TwinSpark) to ground and the cache will work in the SE/30.
Click to expand...
Bolle said:
Spotted that little difference from the IIsi adapter while looking at pics of the SE/30 adapter.
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Good eye!  I was just half way drawing lines in those pics and it was rough with the lines in the layers.  

Can't wait to try to run a wire, after confirming here first if I got it right first of course :-)   

Bolle said:
The external cache setting in the PowerDemo now also reflects the setting in the control panel and turning it on and off has an effect on how fast the shiny stars are redrawn :tongue:
Click to expand...


Yay for fast stars!!! :-D   :-D  

 
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ktkm said:
No C13 as far as I can tell. The top layer doesn't seem to touch the jumpers?
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Nope doesn't seem so (but not home yet to check).

How about this way: can I run a wire in the connection hole or outside to connect C13 to GND (say, two holes up to C11) and try?

slot-layout.png

 
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Hmmm.  I was reading something, somewhere -- maybe in TGTTMFH -- the other day about the IIci external cache.  IIRC, it said that Cache Enable is only active for memory accessess.    So, the first GB of address space?   It makes sense, as you don't want to cache IO operations.   You can't count on I/O data remaining unchanged at a given address.

Anyway, it seems like tying it low so that it is always enabled could cause problems.   Unless I am misremembering which signal it was and there's some other "cache this if you can" signal.

I wish I could remember it better, but I was on a binge of cache information reading.   Kind of a feasibility study for adding an external cache to that pass-through upgrade I picked up for the SE/30 a few weeks ago.

 
Hm, if that’s the case you will never get proper operation of the PowerCache in the TwinSpark adapter.

Pretty sure there is an address decoder on the PowerCache itself that takes care of only caching things that should be cached. The external enable signal does not exist on the socketed PowerCache which uses the same GAL set.

The Daystar Mac II adapter for example also just ties /CENABLE to ground without any extra logic that decodes memory addresses.

@K Trueno a small jumper from C13 to C11 will do. Just make sure before that C13 isn’t connected anywhere else (it shouldn’t connect anywhere according to my info on the TwinSpark but I don’t have one myself to check)

@trag the IIci is special as the memory controller in there can control an external cache. No other machine besides the IIsi has that capability. On the IIsi it needs external decoding logic that’s done by the GAL on the Daystar adapter.

If you take a close look at the SE/30 adapter that GAL is wired up different than on the IIsi adapter. Pin 19 of the GAL connects to /CENABLE. It is set to be low all the time in the fusemap. On the IIsi adapter /CENABLE connects to Pin 18 on that GAL which is only active if the memory controller in the IIsi wants to address an external cache.

 
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Bolle said:
@K Trueno a small jumper from C13 to C11 will do. Just make sure before that C13 isn’t connected anywhere else (it shouldn’t connect anywhere according to my info on the TwinSpark but I don’t have one myself to check)
Click to expand...
I’d love to see that illustrated. Btw, I hooked up a better camera with a tripod, just in case more photos are needed.

 
@Bolle Yup C13 goes no where as far as I can tell.  So I tried it!  Yaaaaah!  Full speed!  Fast stars are fast  :-D

This is a huge discovery for Universal PowerCache users on the SE/30!

IMG_9830.JPG

Screenshot_2019-06-13_07_14_03.png

"Double your computer's speed with a paperclip".  That doesn't happen much these days!

@ktkm Here is a pic of my "jumper" :-D   Yeah its a paperclip right now.  I'll take more pics when I do it right this weekend, but there are markings on the PCB to for you to count (C is top row, there is 10 under the tenth pin, then  count over connect).     

IMG_8796.JPG

 
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K Trueno said:
@ktkm Here is a pic of my "jumper" :-D   Yeah its a paperclip right now.  I'll take more pics when I do it right this weekend, but there are markings on the PCB to for you to count (C is top row, there is 10 under the tenth pin, then  count over connect).   
Click to expand...
Well done @K Trueno @Bolle and @JDW! I’m gonna try it with my TwinSpark tonight! This is the best thing that has happened this year! :)

 
Side note: @Bolle, every time I encounter your skills in these forums, I get amazed about your in-depth knowledge and wisdom. Cheers!

 
Bolle said:
Pretty sure there is an address decoder on the PowerCache itself that takes care of only caching things that should be cached.
Click to expand...
That would make sense and those (or that) Daystar engineers were pretty good.   Is there some mechanism by which the cache can tell whether the SE/30 is in 24 bit mode and the cacheable space is even smaller?   Or are the hardware addresses to memory always the first GB, and the memory maps documented are logical addressing rather than actual hardware addresses.

Bolle said:
The external enable signal does not exist on the socketed PowerCache which uses the same GAL set. 
Click to expand...
That is interesting to know.   How have you confirmed that the GAL set is the same? 

Bolle said:
@trag the IIci is special as the memory controller in there can control an external cache. No other machine besides the IIsi has that capability. On the IIsi it needs external decoding logic that’s done by the GAL on the Daystar adapter.

If you take a close look at the SE/30 adapter that GAL is wired up different than on the IIsi adapter. Pin 19 of the GAL connects to /CENABLE. It is set to be low all the time in the fusemap. On the IIsi adapter /CENABLE connects to Pin 18 on that GAL which is only active if the memory controller in the IIsi wants to address an external cache.
Click to expand...


Thank you for the information.  Interesting, as always.  

The memory controller on the IIci has some limited cache support/control ability, but I don't think it fully controls a cache, as all the caches I've seen for the IIci include some kind of programmable logic (or a big ASIC) which is probably handling BERR and such.   Caches for the NuBus PowerMacs, on the other hand, seem to consist of just a TAG RAM and a regular SRAM (in the needed widths), suggesting that either the NuBus PM memory controller or the PPC601 has cache control logic actually on board.

The PCI Power Macs just seem to have two sets of distinct SRAM, neither of them TAG, suggesting that the comparators have been moved to either the PPC or the memory controller.

However, take the above with a grain of salt.   That's my preliminary conclusions for a fairly rushed overview.   I don't know when I'll ever actually trace connections.

 
You are right... „Control“ may be a bit much. Let’s say the controller knows that there might be cache. The external cache will be able to tell the main memory controller that there was a cache hit so the cache logic doesn’t has to race the standard memory cycles and abort them in between.

Don‘t have the original Daystar adapter so I couldn’t verify the contents of the GAL on there.

However all inputs to the GALs that I could trace from pictures of the adapter are the same inputs as on the IIsi adapter. Most of the outputs I could see do also match (other than the few differences stated above)

That made me think it might be the same.

 
Hard to tell from the pic but double check your C13 connection!  C14 is +5v and that would cause a short.  Otherwise I think you are good! 

 
Bolle said:
Don‘t have the original Daystar adapter so I couldn’t verify the contents of the GAL on there.

However all inputs to the GALs that I could trace from pictures of the adapter are the same inputs as on the IIsi adapter. Most of the outputs I could see do also match (other than the few differences stated above)

That made me think it might be the same.
Click to expand...


I was referring to the PowerCache/030 vs. the SE/30 Socketed upgrade.   I may have misinterpreted, but I took this, " on the socketed PowerCache which uses the same GAL set. " to mean that you had determined that the PowerCache030 with the EuroDIN connector uses the same GAL set as the SE/30 upgrades which plug into the 68000 socket.

Were you perhaps comparing the IIsi/SE/30 adapter(s) to the IIcx adapter in that phrase?   Sorry for the misunderstanding.

 
Awesome stuff going on here. I start to wonder why no one noticed this before.

Like nobody ever had the actual cache on the universal PowerCache working in an SE/30 before I guess (at least without the official adapter)

ktkm said:
I’m gonna celebrate with a cold Czech lager!!! 
Click to expand...
Cheers.

IMG_9217.jpg

And thanks for the kind words earlier today ;)

It's not like I totally know what I am doing, just can't stop digging around once I started.

 
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