PM 8600 reports wrong size RAM?

[jrwil]

I just put in eight 128MB sticks of RAM into my PM 8600, but System Profiler reports that they're all 64MB sticks. All slots are reporting. This is on System 7.6.1. The sticks are clearly marked 128MB. Is this common, do I have mislabeled RAM, or could it be a System 7 issue?

 

[CC_333]

It might have to do with it being double banked RAM?

I know that's a problem with some older models, but I have no clue about the 8600.

c

 

[jrwil]

I read that this issue can crop up if you interleave sticks of different sizes, but these are all the same, so I'm not sure what the cause could be.

 

[MOS8_030]

According to LEM  and Apple the 8600 only officially supports 512mb of ram.

"However, third-parties have discovered that it actually can support 1024 MB (1.0 GB) of RAM with eight 128 MB memory modules."

But it does not say under what conditions or with what memory.

You might try OS 8 or later.

 

[Trash80toHP_Mini]

Everymac's info is no better: *Officially, this model supports a maximum of 512 MB of RAM. However, third-parties have discovered that it actually can support 1024 MB (1.0 GB) of RAM with eight 128 MB memory modules.

Sure sound like it doesn't support double banked memory. See if you can find a spec on the memory module type and look for the DevNote (might be in the upgrade info in the service source as well) for single/double bank spec.

If you can't find the info, trag might be able to tell you which pins/edgecard connection teeth to buzz to determine the organization of the modules.


 


 

 

[trag]

I would try NewerTech's RAMometer utility (also part of their Gauges utility), as a first step.   It's possible that 7.6.1's System Profiler is just ignorant.  System Profiler was pretty new and clunky at that point.

All the X500 machines should support 128MB DIMMs without issues.   If you dig into the Hardware developer Notes' explanation of the supported addresses and banks, 128 MB DIMMs are clearly supported (as clear as it can be when deriving info from memory addressing details).   According to the Hardware Developer note, the 7200 should support 256MB DIMMs, but AFAIK nobody ever made any.  IIRC

 

[jrwil]

Thanks for the tip on RAMometer. It also reports 512MB instead of 1GB (passes the test, FWIW). I might find an OS 9 CD and see if I get a different reading in there.

 

[trag]

Which ROM version is ASP reporting?  Should look something like " $77D.28F2 "   but the 28F2 may be 34F5 or some such.  This will tell me whether you have an 8600 or an 8600 enhanced, or an 8500 board in an 8600 case...   In the latter case, it is conceivable that you have a very early ROM revision which didn't support 128MB DIMMs.   I have seen a very few boards with the earlier ROM revision, but it is total speculation on my part that it might not support the larger DIMMs.

 

[jrwil]

That is interesting @trag, because I was wondering why ASP reports the Model name as "Power Macintosh 8500 series." The ROM revision is $77D.34F5.

 

[trag]

Okay, that's the revision number for the latest Power Macintosh 8600 Enhanced, which uses the Mach V PPC604EV cards.    It should definitely have support for 128MB DIMMs.    It's pretty unlikely that someone would have slipped an 8500 into an 8600 case, as it also involves changing the power supply.   There's not much different between the 8500 logic board and the original (Un-Enhanced) PM8600 logic board except that the power supply connector changed.  The ROM also bumped up from 28F2 to 34F1 but I've never seen any tangible evidence that the ROM revision makes a different.

But the 8600 Enhanced has the 34F5.    So you have the latest and greatest.

Next, can you do a detailed scan of your DIMMs front and back?   We need to be able to read the writing on the actual chips.   Most of the chips will be identical, so if you prefer, you could just count the chips and read off the model numbers for us, instead of providing an image.   This will allow us to identify the memory chips and their capacity (probably) and then multiply by the number of chip, in order to determine the actual capacity of the DIMMs.

If there really is 128 MB worth of RAM chips on those DIMMs then that will be puzzling.

 

[jrwil]

Eight large chips per side.

The chips labeled C1-C16 (side A) and C17-C32 (side B) are marked:

SAMSUNG or SEC KOREA, followed by a number that varies, 943, 937, 946, 925, 112, 040, 943

KM48C8000CS-6 or K4F660811D-TC60 or others.

Reference pic

 

[jrwil]

Both of those model numbers indicate they are 8mx8bit or 4mx16 chips = 64mbit, x 16 = 128MB?

 

[AlpineRaven]

My 8600/250 does have 1gb of RAM - 8x 128gb sticks and is showing 1gb in 7.5.5 so the OS version is irrelevant. 

Cheers

AP

 

[trag]

Very mysterious.  Only remaining idea is to pull all the RAM and install just one stick.  Try it in all eight slots.  Record whether it's detected as 64 or 128.  Rinse, repeat.  Tedious.

If they're all detected as 64MB in every slot, that will be strange.   

At that point (or perhaps before all the tedium) we need a visit to the original x500 Hardware Developer Note and the datasheet(s) for the memory chips.  It's possible we're looking at something like the logic board only supports 12 X 11 (rows X columns addresses) and the memory chips are 13 X 10, so only 12 X 10 addresses are getting used.

 

[jrwil]

I did try a few sticks in some random slots. All reported 64MB.

The Hardware Developer Note states:

"The method of RAM expansion in the new models is essentially the same as in their earlier counterparts: 168-pin, 8-byte DIMMs as defined in the JEDEC MO-161 specification."

Possible these sticks are not "8-byte"?

 

[jeremywork]

I had this exact same problem in my 9600/350 as well as my 8600/200. I have a MaxPowr G4 upgrade which only plays nicely with 162244 type buffers, making finding memory a pain. I found my 16MB and 32MBs report properly, but the 128MBs I purchased all showed as 64MB no matter what configuration I installed them in (OS 7.6.1 and OS 8.6). The manufacturer suggested the motherboard doesn't support double sided modules, but their site specifically advertised them for NewerTech MaxPowr CPU upgrades. I feel like I'm missing something, but haven't got a clue. I ordered three used 128MB 5v FPM modules that had OWC stickers, so when those arrive I'll see if any of them are 162244 buffer compliant and if they read properly in the 9600. Wish I had the answer but it's nice to know I'm not alone!

 

[jrwil]

Very interesting, @jeremywork. My 8600/300 has a Sonnet Crescendo installed, but I do have the original CPU. I will pop that in and see if I get a different reading.

 

[jrwil]

All slots still report 64MB with the stock 604ev. Back to the Crescendo 700. 

In the meantime, swallowed my fondness for System 7 and upgraded to 8.6. The machine now boots reliably and doesn't bomb every time I try to do something interesting!

 

[jeremywork]

Forgot to mention changing CPUs didn't change for me either. 604e/200, 604ev/350, MaxPowr G4/450 all reported 64MB. Definitely a motherboard (or ROM?) problem. The only thing I didn't think to try (didn't know at the time before I returned the memory) is that these motherboards start at the highest numbered slot pairs and count down (A4/B4, A3/B3, etc.) I don't think this should make a difference but I was counting up from A1/B1 and never got a chance to test it properly.

Echo your comment on System 7  I love it but find it much more stable on more moderate systems like my 5500 or PowerBook 3400c. G4 upgrade aside, I think I have too much PCI glory going on in the 9600 for System 7 to play with! (Apple 10/100 | Sonnet Tempo Trio | Grappler 3940UW | OrangePC 660 | Radeon 7000 | Voodoo5 5500)