Maximum RAM for the 6500

[Phipli]

I was wondering if anyone had ever tried a 128MB DIMM in the Macintosh (we know its a Performa really) 6500?

There are footprints on the board for soldered RAM, but they were unpopulated. My thoughts are that one of the bank lines is either connected to the footprints and not the slots, or it might be connected to both.

There is a chance that 128MB DIMMs might work in both slots, or possibly, like the P630, in one of the two slots.

A quick google search and I didn't find any record of someone trying it. We know how Apple liked specifying less RAM than a machine would take (I suspect it was a result of them being sued after the II and IIx wouldn't take high density SIMMs).

 

[Powerbase]

I the unpopolated spot would be for the weird 32MB + 64MB + 64MB setup the tanzania (& tanzania 2) boarda used. Ive tried asking but I dont know of any way to circumvent those maximums.

 

[Phipli]

I the unpopolated spot would be for the weird 32MB + 64MB + 64MB setup the tanzania (& tanzania 2) boarda used. Ive tried asking but I dont know of any way to circumvent those maximums.

I might be misunderstanding, but the 6500 isn't a Tanzania board?

 

[Byrd]

Yep, tried a 128MB DIMM in a TAM/6500, doesn’t work

 

[chelseayr]

phipli the soldered ram might be to do with that most of the pcb layout was "recycled" between the 6400 and 6500 even as much as there were many noticeable changes to the spec between both. the 6400 did indeed have 8mb of ram soldered onboard which amusingly added up the total ram to 136mb instead of 128mb

 

[Phipli]

Yep, tried a 128MB DIMM in a TAM/6500, doesn’t work

Ah, shame - did you try both slots?

Technically it might be possible to run wires from the soldered RAM footprints to the slots to add the missing bank selects.

 

[Phipli]

phipli the soldered ram might be to do with that most of the pcb layout was "recycled" between the 6400 and 6500 even as much as there were many noticeable changes to the spec between both. the 6400 did indeed have 8mb of ram soldered onboard which amusingly added up the total ram to 136mb instead of 128mb

Even so, there was a chance that the bank selects were wired to both, so the footprints being unpopulated might have meant 128MB DIMMs worked. Apple are poor at stating tje real Maximum. The P630 info says 32MB SIMMs max, but will actually take a 128MB SIMM.

Byrd has tried it though and it didn't work, so as a minimum, bodge wires are needed from the footprints to the unconnected pins on the RAM sockets.

 

[Byrd]

Ah, shame - did you try both slots?

Technically it might be possible to run wires from the soldered RAM footprints to the slots to add the missing bank selects.

Yes, both slots single 128MB stick did not work - that’s it for the memory controller I believe. I wanted a single stick to improve cooling around a L2 G3 card at the time, now using a fan nearby

 

[chelseayr]

byrd mm well the cache slot was either located away from the dimms or at least mounted on the "facing away from it" side on most non-performa boards unlike that the performa boards seem to always have the cache slot placed that it actually faced the dimms so I suspect that technically the bigger l2-based accelerators probably were really designed for the former kind of installs? (I mean a 740@200mhz is 6w which somewhat seem ok being next to ram in these densely-packed desktop cases perhaps but a 750@300mhz is already 9w and I can't imagine any sort of l2-based g4 cards liking directly facing the dimms

thats just my own thoughts on this especially after rechecking mackido for the thermal numbers and re what I already recall of boards layouts

 

[Powerbase]

I might be misunderstanding, but the 6500 isn't a Tanzania board?

Tanzania and Tanzania II Motherboards | Low End Mac

lowendmac.com

It used a modified Tanzania design. Even clones that used the Tanzania II board had the same RAM limitations. Both boards used the same memory controller, I assume.

 

[Phipli]

Yes, both slots single 128MB stick did not work - that’s it for the memory controller I believe. I wanted a single stick to improve cooling around a L2 G3 card at the time, now using a fan nearby

Yeah, same issue, I managed to find a pair of extremely skinny 64MB DIMMs in another machine thankfully.

 

[Phipli]

byrd mm well the cache slot was either located away from the dimms or at least mounted on the "facing away from it" side on most non-performa boards unlike that the performa boards seem to always have the cache slot placed that it actually faced the dimms so I suspect that technically the bigger l2-based accelerators probably were really designed for the former kind of installs? (I mean a 740@200mhz is 6w which somewhat seem ok being next to ram in these densely-packed desktop cases perhaps but a 750@300mhz is already 9w and I can't imagine any sort of l2-based g4 cards liking directly facing the dimms

thats just my own thoughts on this especially after rechecking mackido for the thermal numbers and re what I already recall of boards layouts

Yeah, the cache slot is right next to the RAM and the heatsink contacts thicker RAM DIMMs and causes them to lean. The AVID cable goes over the top too, but after hours of running the G3 only reached 53°C on a warmish day, so I'm happy enough. Warmer than my PCI Sonnet, but not the end of the world.

G3 heat generation depends on the revision too, I read somewhere that 500MHz ones were 6W, but I didn't verify that with datasheets