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Dimitris1980

Performa 6116 video and sound issues

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I had at the ice for some months my performa 6116 because i was using my LC475. Yesterday i connected it again and i change the pram battery because the old one was dead. I did a fresh format and installation of mac os 8.1 but i have some issues. I have an apple 8100 video card with 4mb ram and i connected it to a 15" samsung monitor SyncMaster 152v via a mac-vga adapter. The best i get is 832x624 resolution with million colours. I tried to change the connectors of the adapter. Some times i don't get a screen at all and only once i managed to have 1024x768 resolution but with thousand of colours, not millions. Which connectors must be on to have the best of the resolution and colours? Second issue is the sound. All this years i was getting sound only from my external speakers. Now i have to turn on the built in sound and i have both of the machine internal speaker and of the external. If i choose the mute then i do not have sound at all. I want sound only from the external speakers, not the built in computer. What can i do?

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Well, i did a fresh install of Mac OS 8.1 and Mac OS 8.5.1. I have three partitions in my hard disk. At the 3rd partition i will install Mac OS 7.6. The sound is ok now. The only thing i want to check is the resolution and the colours. Can i have million colours at 1024x768 resolution with this monitor which is connected to my apple 8100 video card? I use my performa for games and with the sonnet g3 500 mhz installed is really a beast. I guess it is not necessary but i would like to push the machine more. Now, I have my LC475 connected to the macintosh colour display where the resolution is fixed 640x480. So, with the other monitor connected to Performa, i can play some games that require at least 800x600 resolution with thousand colours. Some say that the Radius Thunder GX IV is nice card but it is difficult to find one.

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I still think that Steven Kan is a little to credulous about the reports of 520MB  RAM in the 6100.    He says he's had two separate reports, so maybe it's true, but I've traced the memory pins in the SIMM sockets of the PM6100, and I can't see any way one could address a 256MB SIMM.

 

A 72 pin SIMM is 4 bytes wide in data (32 bits).   It has 12 address lines which are multiplexed (used twice) to supply addresses.  So there are 22 bits of address.   This creates 24 bits of addressing which translates into 16M addresses.   With 4 bytes at each address, one can directly address 16M X 4bytes = 64MB of RAM per SIMM.

 

Then they do the fun trick of banks on 72 pin SIMMs.  Banks are distinguished by only activating some RAS signals when supplying the Row Address (one of the two uses of those 12 address bits).    There are four RAS lines on a 72 pin SIMM, and the RAS lines are encoded in a one hot fashion, so, in theory, one could have four banks, one for each RAS line on a SIMM.    

 

If one had four banks and each bank was 64MB, then one could actually have a 256MB 72 pin SIMM.   The problem is that on the 6100 logic board, the RAS lines in each SIMM socket are tied together in pairs.   So only two distinct RAS signals are available, limiting one to two banks of 64MB = 128MB SIMM maximum.

 

Taking this still further, it is conceivable that the RAS lines are not being encoded as one-hot, if that's the case, then one could still get four banks (00, 01, 10, 11 on the RAS signals) on the SIMM.    But that require logic on the actual SIMMs to decode the RAS signals for the memory chips, and vastly more farfetched, it would require that Apple wrote code in their firmware to support binarily encoded RAS signals in their memory.

 

I mean, it's possible, but really really farfetched, given that they've never supported such a thing any where.

 

All that said, his 6100 page is excellent, except for that one little nitpick.

 

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@trag

i was actually hoping to put two 128mb sticks in my 61xx. You think they will not work (or address the full space)? I am hopeful based on the fact that the 575 logic board can address a 128mb SIMM on its 72pin slot.

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The 128 MB SIMMs should work fine.  The TLDR for my above post is that the wiring is there for 128MB SIMMs, but not for 256MB.  :-)

 

However....

 

In my experience, 128MB SIMMs often don't work.   The reason, I believe, is as I mentioned above.  Apple ties their RAS lines together in pairs.  Typically, on a 128 MB SIMM the RAS lines are also tied together in pairs.    Which is fine, if the pairs correspond, and a big fail if they don't.

 

For example, if I have RAS lines 1, 2, 3 & 4 and the 6100 logic board ties together lines 1 & 2 and then lines 3 & 4.  Then whatever line 1 sees, line 2 sees.  And vice versa.  Similarly for 3 & 4.

 

If the SIMM ties RAS lines 1 & 2 together and ties 3 & 4 together, then everything is great.    The logic board sends a signal on RAS 1 or 2, and RAS 1 & 2 on the SIMM sees it.   RAS 3 & 4 don't.   The logic boards sends a signal on RAS 3 or 4 and on the SIMM RAS 3 & 4 sees it, and 1 & 2 don't.   Everything is working great, and the RAS pairs are distinct.

 

However, if the SIMM ties together RAS lines 1 & 3 and also 2 & 4, now let's look at it.

 

Logic board sends a signal on RAS 1 or 2.  Because they are tied together on the logic board, RAS lines 1 & 2 both see this signal at the SIMM.    Because the SIMM ties 1 -> 3 and 2 -> 4, this means that all four RAS lines see the signal.    The Banks of the SIMM are no longer getting distinct RAS signals.

 

I mainly purchase the HP D4893 and D4290 (can't remember which one is 128MB) SIMMs and they don't work in the 6100, although they work great in the Q605/LC475/LC476.   I suspect, but never got around to checking, that the RAS lines are tied together in the opposite pattern.   There are some little SM resistors on those SIMMs too, and if I ever get back to that investigation, I'll check to see if those resistors control which RAS are tied togehter.  Those SIMMs might work just by moving two resistors.

 

It's also possible that the CAS lines are involved in some way, but from what I can tell, those should only be used to control byte-wise selection, not addressing.

Edited by trag

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Until yesterday everything was working perfectly. The problem now is that i do not hear sound from the external speakers when i restart from Mac Os 8.1. I have 3 partitions on my hard drive, in the one i have games and programs installed, in the other i have mac os 8.1 installed and in the third one i have mac os 8.6 installed. When i run mac os 8.1 the sound is always muted and when i turn it on i can hear sound only from the macintosh built in sound. From the external logitech speakers that i have connected there is no sound at all. When i run mac os 8.6 the sound works perfectly. Is there a solution for this?

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Quote

I still think that Steven Kan is a little to credulous about the reports of 520MB  RAM in the 6100.    He says he's had two separate reports, so maybe it's true, but I've traced the memory pins in the SIMM sockets of the PM6100, and I can't see any way one could address a 256MB SIMM.

If there even was a hardware possibility to address 256 SIMMs in PM 6100, you'll still need to overcome the software limit of 128MB! I can say it with a high degree of certainty because I performed an excessive analysis of the firmware in the past as part of the MAME emulation project.

When the PM 6100 is powered on, the HW initialization procedure located in ROM performs the so-called memory bank sizing - that is, it writes some bytes into each RAM page and read them back to verify that the physical memory is actually there. The parameters for that sizing have been hardcoded for the whole Nubus family.

 

For the PM 6100, the following values are stored:

 

Number of physical RAM banks: 3

Bank 0 (soldered onboard memory): phys_addr = 0x0, size = 0x00800000 (8 MB)

Bank 1: phys_addr = 0x08000000, size = 0x08000000 (max. 128 MB)

Bank 2: phys_addr = 0x10000000, size = 0x08000000 (max. 128 MB)

 

As you see, there is no possibility to plug RAM SIMMs bigger than 128MB into PM 6100 - it won't be physically possible to access that extra memory. Reprogramming the ROM to change the hardcoded values will be of no avail.

 

The maximum possible RAM capacity for PowerMac 6100 is therefore 264 MB (128 + 128 + 8 MB).

 

For PM 7100 and 8100, the max. bank size is 32MB according to memory sizing parameters...

Edited by powermax

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BTW, there is a typo in my first March 9th post above.   I wrote " So there are 22 bits of address." where I meant to write "So there are 24 bits of address."

 

In my Second March 9th post above there is a slight error in my report of how the HP 128 MB SIMMs are wired.  See note at * below if interested.*

 

The PM7100 and PM8100 do something unnatural to the upper address and RAS signals to add extra SIMM sockets, in hardware.   The end result is, as you write above, they can only address 32MB per SIMM.    This is also a hardware limitation.    The software limitation is probably there, because they knew the hardware limitation was there.

 

In the PM6100, the 12 address wires and the four RAS signals run directly from the memory controller chip (one of the big square ASICs) to the two SIMM sockets.    Addressing and bank control is straight forward and just as one would expect.

 

In the PM7100 and the PM8100, the upper address signal and the RAS signals run through what looks like a medium sized CPLD, before they emerge and run to the SIMM sockets.     I don't have my notes handy, so this is from memory, but they basically sacrificed the 12th Address bit in order to be able to address more SIMM sockets.

 

So, instead of having 24 address bits available (12 row, 12 column) they only have 22 (11 row, 11 column) and so bank sizes are limited to 16 MB (22 bits => 4M X 4bytes (width) = 16 MBytes)  instead of 64MB.   Or maybe they sacrificed the upper two row addresses, so it's really 10 row, 12 column.    I would have to check my notes.

 

Anyway, the SIMMs are still double banked, so one gets 32 MBs per SIMM.   32 MB SIMMs  are typically built as two banks of 16MB.

 

PowerMax is using the term "bank" a little differently than me.  In his posting, it refers to SIMM size.   But a single SIMM can have more than one addressable bank on board, so it's useful to use the term "bank" to refer to the addressable subunits on a SIMM.

 

Anyhoo, that CPLD that eats the raw high end address bits (can't remember if it eats one or two, I think two) and the RAS signals and spits out the RAS signals for all the SIMM sockets, is the reason that the PM6100 can address 128 MB SIMMs (2 banks X 64MB) and the PM7100 and PM8100 can only address 32 MB SIMMs (2 banks X 16MB) even though all three machines have exactly the same memory controllers.

 

It sounds like the firmware was written to reflect the hardware limitations, so even if there was a way to rewire the 7100 or 8100 to work like a 6100, there would still be a firmware limitation to overcome.

 

There really wouldn't be any benefit in an 8100 to modifying the memory wiring.   The family just won't go above 264MB.   

 

In theory, it should be possible to modify the 7100 to address 264MB.   Probably, take out the CPLD, run the (11th and?) 12th address line directly to all four SIMM sockets, and split the RAS lines to each SIMM socket.   Then tell the firmware that it's really a 6100 (or modify to take out the 32 MB limitation) and install 64MB SIMMs in each SIMM socket.  

 

Or do the above, but sacrifice two of the SIMM sockets, wire the other two identically to the 6100 and install 128 MB SIMMs.  Again, with firmware mods.

 

* The problem isn't how the RAS lines are tied together on the SIMMs, because they aren't.  The problem is that RAS 0 is tied to half the chips in bank 0.   RAS 1 is tied to half the chips in bank 1.  RAS 2 is tied to the other half of the chips in bank 0.   RAS 3 is tied to the other half of the chips in bank 1.    The problem is that the way the 6100 ties its RAS lines together is that one ends up activating the bottom half of bank 0 with the bottom half of bank 1 (they're on the same data pins).   And also one activates the top half of bank 0 at the same time as the top half of bank 1.    That just doesn't work.   If the RAS arrangement activated the bottom and top halfs of bank 0 at the same time, or the bottom and top halfs of bank 1 at the same time, or even if they activated the bottom half of bank 0 and the top half of bank 1 at the same time, it would work.    But activating two sets of chips that are both connected to the same data lines, and not activating any of the chips connected to the other half of the data lines, does not work.

 

 

Edited by trag

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On 3/11/2018 at 10:42 AM, Dimitris1980 said:

When i run mac os 8.1 the sound is always muted...From the external logitech speakers that i have connected there is no sound at all.

In the Sound control panel, go to output and verify that output is set to line out. My 6100 series running 8.1 also seems to default to internal speaker, even with external speakers plugged in. I was able to resolve that from the control panel.

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