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Unread postPosted: Tue Mar 16, 2010 9:12 am 
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mapesdhs wrote:
Does anyone have a copy of NeZetiC's images/article? Looks like his domain is gone byebye.
A snapshot of the site from August 2008 is still available via the Way Back Machine <today, anyway - but only that single day's snapshot - so you probably better not drag your feet>..

How's your French? NeZetiC.info: SGI O2 Overclocking : de R10K à R12K

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Unread postPosted: Tue Mar 16, 2010 9:25 am 
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Thanks!! 8)

I'm also trying to find an image of the Octane dual-PM which shows the other resistors that would need to be changed
for a 250->350 overclock. The images in the dual-300 overclock gallery don't show all the resistors. Naturally, all
of Joe's images are long gone.

EDIT: no need now, sorted it out. Will do some decent scans at some point, add them to my site somewhere.

Ian.


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Unread postPosted: Wed Mar 17, 2010 3:10 pm 
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My Website is still running. I've only lost the .com domain name.

http://www.nezetic.net/index.php?id=38

If you have any question, do not hesitate to PM me.

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Unread postPosted: Wed Mar 17, 2010 6:48 pm 
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Thanks!! For the moment though I'm focusing on the dual-250 mod; built two modules so far.

Ian.


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Unread postPosted: Sat Oct 30, 2010 3:33 am 
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Sorry to resurrect an old thread...

Does anyone know which resistors to change to set a 3.5X multiplier on an O2 module?

I've built the R12K/300 modded module ok, the pictures in this thread are fine for that (3X multiplier), but I'm
not sure what needs to be moved to change it to 3.5X.

Some benchmark results for the modded 300 module are now on my site (Lynx compilation, RC5 and movie
conversion), performance is identical to an original 300.

Ian.

PS. Just looking at my previous post - the modded Octane modules pretty much worked out ok (dual-R12K/350)
but with one peculiar exception: they passed all the benchmark tests on my site, including the 'heavy' tests like
the Alias render, but trying to clone the system disk onto another drive with xfsdump/xfsretore would almost always
cause a cache error. Wierd...

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Unread postPosted: Sat Oct 30, 2010 12:35 pm 
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Ian - what are the cache chip speed differences between 250/1MB and the 300 modules? I'm looking into doing this on my Octane with an O2k/300 PIMM-sourced R12k, but will leave the PIMM intact if it looks like things aren't going to work.

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Unread postPosted: Sun Oct 31, 2010 1:48 pm 
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Er, not sure offhand. It was some months ago I was fiddling with the Octane modules.I'm focusing more on O2 now.

Ian.


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Unread postPosted: Tue Nov 16, 2010 6:19 pm 
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Today someone asked me about the O2 mod images, so I thought I'd scan in my own diagram I made for changing a 250 module into a 300:

http://www.sgidepot.co.uk/o2/o2modresis ... to_300.gif

Hopefully that's a bit clearer than some other descriptions I've seen.

However, I still don't know what resistors to move in order to have a 3.5X multiplier (to get 350MHz). Anyone know?


Also, does anyone know if the core from an Octane 360 module could be used to get an O2 425? (ie. by moving the core into what was
an original O2/300 module).

Plan:

1. Convert orig O2/300 modules into O2/400 or 425 (whatever's possible if I can use a 360 core from an Octane module).
2. Used the 300 cores removed from O2/300 modules to convert orig O2 250 modules into either 300 or 350 (whatever works best).

I figure one couldn't move a 360 core into a 250 module as the cache would be too different, yes?

I have a couple of 360 modules I can expt with. However, I'd need to know a bit more about the multiplier resistor positions to try it.

Ian.

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Unread postPosted: Tue Nov 16, 2010 7:02 pm 
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So are the O2 300 modules' R12ks BGA?

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Unread postPosted: Tue Nov 16, 2010 7:16 pm 
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I highly doubt it... I was under the impression from earlier comments that the BGA stuff didn't start until the 400 speeds. Hence why I
wonder about being able to fiddle with a 360. An O2/425 would be nice. Orig 400s are too valuable to stick in hobbyist systems.

Ian.

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Unread postPosted: Tue Nov 16, 2010 11:35 pm 
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mapesdhs wrote:
I highly doubt it... I was under the impression from earlier comments that the BGA stuff didn't start until the 400 speeds. Hence why I
wonder about being able to fiddle with a 360. An O2/425 would be nice. Orig 400s are too valuable to stick in hobbyist systems.

Ian.



I thought it was anything over 300. Anyone with a 350 MHz PIMM who can check it out?

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Unread postPosted: Wed Nov 17, 2010 1:35 am 
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Oh! In that case I'll open up a 360 when I can find a moment... though if it's over 300 then by definition a 300 should be ok.

Ian.


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Unread postPosted: Wed Nov 17, 2010 9:44 am 
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mapesdhs wrote:
I figure one couldn't move a 360 core into a 250 module as the cache would be too different, yes?

I have a couple of 360 modules I can expt with. However, I'd need to know a bit more about the multiplier resistor positions to try it.

Ian.


I think I might have found your problem with the Octane PM20s upgraded from 250.

It appears that SGI used a 1:1 ratio for the cache for 250 and under, while 300 (at least for Origin) uses 5nS SRAMs for a 200MHz cache clock (2:3). Unless you swap out the setup SEPROM with one that changes the cache timing it seems you're running the 250MHz cache at full processor speed when you bump it up to 350, and I don't think the SRAM has enough tolerance. Note I haven't actually opened up my PM20 yet, so this is mostly conjecture based on documentation and hinvs. 250MHz would require 4nS chips, 300 would require 3.3nS, and 350 2.8nS (for a 1:1 divisor), and my guess is there isn't quite enough headroom in the 250s cache chips. If you have a 2MB dualie and 2MB 300 singlies you can pull the SEPROM and swap that as well and you should be good (a 1MB dual 250 would need a reprogram to deal with the different cache size, as would the chips from the Origin PIMMs w/ 8MB SC).

I so need an EPROM programmer :(

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Unread postPosted: Wed Dec 01, 2010 3:32 pm 
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Two cents worth on the O2 CPU modules.

With the exception of the 400 MHz R12k, I think they were all the removable CPU's. Once when I was messing with a module, I got the machine to start booting at 400 MHz (with a 300 MHz chip) but it didn't get very far. A good R12k-300 chip will usually run at 350 reliably, but not much more as you're running into process limits on the silicon. I've found with the Octane modules that I don't think I've had one that had any cache issues assuming your chip will run at 350, and from what I've seen the O2 modules are similar. 350 is probably the highest safe overclock then for an R12k module. Anything below 250 MHz doesn't have the necessary split-plane power supply and can't really be upgraded, so they're basically called 'test modules' around here.

Of interest is modding an R12k-400 to 450 MHz, but I only have one module and would hate to break it, as they're quite rare these days. Probably be the worlds fastest O2 at that point.

I did a lot of messing around with cache speeds on the Octane. There is a single CPU module - originally a 400 - kicking around out there I did quite some time ago, and think it ran at 470 MHz with the stock cache divider. This is the exception rather than the norm.

Attached is my little cache-speed calculator for Excel, it takes the actual 'resistor divider' number and module crystal frequency, and spits out the final CPU clock and cache speed.


Attachments:
SGICache.xls [13.5 KiB]
Downloaded 27 times

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Unread postPosted: Wed Dec 01, 2010 4:47 pm 
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SAQ wrote:
mapesdhs wrote:
I figure one couldn't move a 360 core into a 250 module as the cache would be too different, yes?

I have a couple of 360 modules I can expt with. However, I'd need to know a bit more about the multiplier resistor positions to try it.

Ian.


I think I might have found your problem with the Octane PM20s upgraded from 250.

It appears that SGI used a 1:1 ratio for the cache for 250 and under, while 300 (at least for Origin) uses 5nS SRAMs for a 200MHz cache clock (2:3). Unless you swap out the setup SEPROM with one that changes the cache timing it seems you're running the 250MHz cache at full processor speed when you bump it up to 350, and I don't think the SRAM has enough tolerance. Note I haven't actually opened up my PM20 yet, so this is mostly conjecture based on documentation and hinvs. 250MHz would require 4nS chips, 300 would require 3.3nS, and 350 2.8nS (for a 1:1 divisor), and my guess is there isn't quite enough headroom in the 250s cache chips. If you have a 2MB dualie and 2MB 300 singlies you can pull the SEPROM and swap that as well and you should be good (a 1MB dual 250 would need a reprogram to deal with the different cache size, as would the chips from the Origin PIMMs w/ 8MB SC).

I so need an EPROM programmer :(


For an Octane PM, it's still resistors, Shown is the 1.5 and 2.0 positions, useful for all but the slowest PM's. The duals are similarly configured, though the BGA dual boards have a slightly different layout.

http://www.nekochan.net/wiki/gallery2/v/SGI_ ... d.jpg.html

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