Is there a way to increase the 136MB RAM limit in the Power Mac 6100 and 7100

[trag]

I would love to learn more about that extra chip. Is it an off-the-shelf IC or an ASIC?

I don't have any X100 boards where I can lay hands on them, but from what I remember, the chip was labeled with an Apple part number, but it's entirely possible that it was a rebadged CPLD. I checked my notes, but I didn't record the part number. Electrically, it's going to sit between the RAS and CAS lines and the 0802 chip which is one of the big ASICs in the chipset. And, of course, the 6100 lacks the chip in question. I think that the Q840AV does the same thing. It certainly behaves the same way, as far as memory operation goes.

 

[dust bunny]

Thanks for your detailed reply!! I'm not sure why I thought I had 128MB SIMMs, I actually have 2x 64MB SIMMs. So the 136MB reading makes sense now. Interestingly the 6100 will only recognise the sticks if they are installed as pairs. When only only one SIMM is present the 6100 only recognises the 8MB onboard memory. I haven't come across this with lower capacity SIMMs.

That's a shame about the 7100, I'm not skilled enough to make any adjustments on my board. Thanks for the info I appreciate it. Now to find the correct 128MB SIMMs!

obsolete was "thinking of building some 16MB 30-pin RAM SIMMs out of some surplus, unknown condition 128MB 72-pin SIMMs" which very nearly made me cry.
https://68kmla.org/bb/index.php?threads/do-32-pin-400mil-soj-sockets-still-exist.46766/#post-525017

256MB sticks also exist, but I think they're all ECC.
I have seen the Low End Mac page that alledges 2 people have fitted 256mb sticks to have 264mb total ram. Not sure if the repprts were acurate, and I guess they'd need custom modified ECC deleted sticks, if it ever actually happened?
On a side note, the 8MB soldered on the board. Has anyone swapped them for larger capacity chips, theoretically 32MB appears possible (at a very cursary glance) and maybe more?

 

[Phipli]

Not sure if the repprts were acurate, and I guess they'd need custom modified ECC deleted sticks, if it ever actually happened?

Macs usually just ignore parity - is it the same with these?

 

[dust bunny]

I was always told they wouldn't work with ECC/parity modules, but I've never tried.
Anyone actually know?

 

[Phipli]

I was always told they wouldn't work with ECC/parity modules, but I've never tried.
Anyone actually know?

Beige macs don't utilise parity (mostly), but parity simms do work as normal simms. I'm just been careful here because I don't think ECC and parity are the same thing and am not sure which you meant.