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Brett B.

LC630 DOS Compatible supports 64MB SIMMs - 84MB total!

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I got two of these 64MB 72 pin SIMMs quite a while back and finally got around to using them.  One went into my LC475 where it worked great, and not unexpectedly.  The other was destined for my LC630 DOS Compatible machine which allegedly has a ceiling of 52MB - 32 in one slot, 16 in the other, and 4MB onboard.  I know for a fact that the 16MB card is the absolute max for the first slot (tried a 32MB stick in it, no luck) but the second was unknown.

 

Now we know!  Can't promise YOUR Q/LC630 will support these, but mine does.  SUPER excited about this.

 

large.KIMG1370.JPG.29ab2c5165a3af54785bd6276031d300.JPGlarge.KIMG1371.JPG.9ca3d55952516070f2c87e31e6faa3f6.JPG

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Yeah, the Mac side will support a 64mb ram stick, but the PC side not so much. The 630dos board is the same board that comes in a lc 580, with the main difference being that it has an extra ram slot when compared to a regular 630.

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Just for fun I ordered a 128MB SIMM.  We'll see if that works, 148MB memory would be dope.

 

I will have to try the 64MB stick on the DOS card.  I'd be shocked if it works.  I was surprised that it worked on the Mac side.

 

I also tried two Kingston 64MB SIMMs in my 6200/5260/120 machine and only 64MB was recognized there.  Odd.

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Well, it appears that it also supports 128MB modules!  Sweet!

 

I also have confirmation that the DOS card definitely does NOT support my 64MB stick.  It showed up as a 16MB module.  32MB works fine.  Kinda weird but whatever.

KIMG1390.jpg

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Actually, all of these motherboards which have two SIMM slots support one single bank SIMM and one dual bank SIMM, so you can have a 64 meg SIMM and a 128 meg SIMM, plus the four on the motherboard for a total of 196 megs.

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Hmm, now to find a 64MB single bank SIMM.  I know the 32MB and 64MB ones I have now will not work in the single bank slot.  

 

FWIW this 128MB stick I got was from "memorymasters" on eBay and is FPM, non-parity, 60ns

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If you have a RAM check utility, try it and see if it shows memory segmented into 4 Banks?

 

4MB on the floor should be Bank A

16MB Single Bank slot would then be Bank B

128MB Dual Bank slot would then be Banks C and D

 

If anyone knows of a RAM test utility that does show memory as grouped in banks, please let us know. Long time curiosity has been whether disabling Bank A and patch wiring CAS and RAS lines from it to the Single Bank socket might have its support level upgraded to equal to the more capable slot. :huh:

 

 

edit: don't have a DOS board and my first release Quadra 630 lacks both the second slot and the video connector required for DOS Compatibility. If/when I find my Q630 board I'll be trying this with a 72-pin to 72-pin SIMM Saver.

Edited by Trash80toHP_Mini

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On 2/9/2019 at 1:13 AM, 360alaska said:

The 630dos board is the same board that comes in a lc 580, with the main difference being that it has an extra ram slot when compared to a regular 630.

Does your 580 board have the video connector slot for the DOS board next to the battery?

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On 2/16/2019 at 3:36 PM, Brett B. said:

Hmm, now to find a 64MB single bank SIMM.  I know the 32MB and 64MB ones I have now will not work in the single bank slot.

When I found a bunch of 128 meg SIMMs on eBay for $8 apiece, I bought a bunch because they'll definitely work as 128 megs in dual bank slots and as 64 megs in single bank slots. Sometimes it's better than trying to find the right kind of 64 meg SIMM.

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4 hours ago, johnklos said:

When I found a bunch of 128 meg SIMMs on eBay for $8 apiece, I bought a bunch because they'll definitely work as 128 megs in dual bank slots and as 64 megs in single bank slots. Sometimes it's better than trying to find the right kind of 64 meg SIMM.

That makes sense, with the right 128 MB SIMM, if the machine can only read one bank in the slot it's in, it will appear as a 64 MB SIMM.

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What's the technical reason for limiting one slot to single bank only and not the other? 

 

I looked around a little and it appears that the 64mb modules are going to be hard to find. Maybe I'll order up a couple more 128mb ones sometime. I'm tempted to try one in the LC475 now, I bet it works. I'm still surprised that the 6200/5260 maxed out at 64mb though 

 

 

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The LC475 can take 64 and 128 meg SIMMs just fine.

 

I think the idea is that the IDE Quadras only have four banks of memory total, so one bank is the 4 megs on the motherboard, the other is the single bank SIMM socket, and the other two are the dual bank SIMM socket.

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37 minutes ago, johnklos said:

The LC475 can take 64 and 128 meg SIMMs just fine.

 

I think the idea is that the IDE Quadras only have four banks of memory total, so one bank is the 4 megs on the motherboard, the other is the single bank SIMM socket, and the other two are the dual bank SIMM socket.

Bingo

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Interestingly, that should mean with the 4 MB on the board, you could replace it with 64 MB, using the same number of chips. As long as the proper number of address lines are hooked up to that bank to support that much memory correctly. I would imagine it should be because banks A & B should always be wired up to support the same amount of memory as C & D. If not, that would be rather odd.

Edited by Paralel

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15 hours ago, Brett B. said:

What's the technical reason for limiting one slot to single bank only and not the other?

 

RAS signal lines.   Row Access Strobe.     There are only so many independently controlled RAS lines from the memory controller chip.    The 72 pin SIMM specification provides for four RAS pins.   If these pins are independently controlled by the host machine, and wired separately on the SIMM, then up to four independent banks of memory can be installed on a 72 pin SIMM.  In practice, I've never seen more than two banks per SIMM.

 

On a single bank SIMM socket, one RAS signal from the memory controller is fanned out to all four pins on the SIMM socket.

 

On a double bank SIMM socket, two RAS signals from the memory controller are each connected to two of the RAS pins on the SIMM socket.    If the wiring on the actual SIMM doesn't agree with how the socket is wired, then the SIMM may not work.   E.g., Socket pairs 1 with 3, and 2 with 4.    The actual SIMM pairs 1 with 2, and 3 with 4.    I've seen this when trying to use the HP D4893, 128 MB SIMM, in the PM6100.

 

On the LC/P 63X which has two SIMM sockets,, one socket wires all of the RAS lines together, only uses a single RAS line from the memory controller, and only supports one bank.  The other socket separates the RAS lines into two pairs and uses two RAS lines.    As mentioned above, another RAS line is reserved for the soldered-down memory bank.

 

There is some hazard in using a two banked SIMM (e.g. 128MB) in a single banked socket.    In that case both banks on the SIMM are being activated with every transaction.   So on Reads, two different memory chips are trying to drive each of the Data signals.   They should be driving it to the same thing, but this can still cause problems.   

 

Two banked 64MB SIMMs are pretty rare, so I'm surprised to read that it does not work in the single banked SIMM socket.  If the problem truly is its double bankedness, then it should be seen as 32MB.

 

There aren't any right now, but the HP D4290A is a 64MB single banked 72 pin SIMM.   

 

I have not bought these, but they claim to be a pair of 64MB SIMMs built with 8 chips, which would have to be a single bank of 16M X 4 chips.  There's a small chance they are double banked with 8M X 8 chips, but I'm not sure anyone manufactured 8M X 8 chips.   The photo is no help, as it shows the chips for a 4MB SIMM. 

 

https://www.ebay.com/itm/128MB-2X64MB-MEMORY-16X32-72PIN-NON-PARITY-FPM-60NS-5V-RAM-SIMM/131808663007?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

 

As John wrote above, the two slot LC63X should support 128MB in the double banked slot and 64MB in the single banked slot, for 192MB of RAM plus the MB RAM.    

Edited by trag

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14 hours ago, Paralel said:

Interestingly, that should mean with the 4 MB on the board, you could replace it with 64 MB, using the same number of chips. As long as the proper number of address lines are hooked up to that bank to support that much memory correctly. I would imagine it should be because banks A & B should always be wired up to support the same amount of memory as C & D. If not, that would be rather odd.

 

It should be possible, but adding the necessary wires to hook up a 72 pin SIMM would be a mess.   There could be a spoiler in the ROM that always expects to map the memory controlled by that RAS to a 4MB space.    I imagine bbraun (?) could defeat that easily enough, though.

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If the Q630 memory bus is set up so Address, Data CAS and RAS lines of 16MB Bank (we'll call it B?) are a superset of/an extension of the lines from the F108 Memory Controller to/through the 4MB Bank (We'll call it A?) DIP memory on the logic board, the patch wire count could be very reasonable. I see the bus fanning out from controller to DIP Bank A and on to SIMM Bank B and on again to Banks C and D on the Double Banked SIMM. Most of the Bank B bus likely passes through the pads of the logic board memory, with the remainder skirting past/slithering through the DRAM ICs.

 

CAS should be shared between Banks A & B, no? So you'd need the RAS lines of Bank A patched to the SIMM socket of Bank B and probably another pair of Address lines lines that might be patched from the Double Banked SIMM Socket to the appropriate pins of the Bank B socket.

 

I'm extrapolating from MDU Banks A/B in the IIsi schematic. I should probably look at the four bank setup in the IIci schematic before taking a stab at this, but what the heck. :) trag? :huh:

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@trag looks like the Quadra 630 should be set up with four 64MB banks of memory going by the A0-A11 setup, which is the same as the 64MB banks of SE/30 and IIsi if memory serves. That would leave two(?) address lines missing from Bank A, but present on Bank B? Looking at F108 (Rapier) in the 5260 DevNote, it's set up with latches for memory and data connected to the pair of 72-pin SIMMs.

 

There's no system board memory to bollux the first SIMM in the 5260, what we're calling Banks A & B on the Quadra 630/DOS. Extrapolating from that, patching RAS lines only from Bank A DRAM to the Bank B SIMM socket might be all that would be necessary to support 128MB in that socket?

 

There are a couple of other complications in using MDU to theoretically model F108, but what have you got to say about that thus far?

 

https://cdn.preterhuman.net/texts/computing/apple_hardware_devnotes/Mac LC-Quadra 630.pdf

https://cdn.preterhuman.net/texts/computing/apple_hardware_devnotes/PowerMac 5260.pdf

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If I'm following you, then yes, the most elegant way of getting four 64MB banks installed on a P/LC 63X machine would be to remove/disable the motherboard RAM, and route the motherboard RAM's RAS line to the SIMM socket which has only a single RAS.   One would need to explore whether all four RAS to that socket are tied together.    If so, two of them need to be separated electrically and linked to the RAS from the MB RAM.   

 

I'm not sure about CAS being common.   Each bank may have its own CAS as well (may be necessary for refresh control), so the CAS from the MB RAM might need to be rerouted to the single bank SIMM socket as well.

 

Then, yeah, just install two 128MB SIMMs and Bob's your uncle.

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