• Hello, Guest! Welcome back, and be sure to check out this post for more info about the recent service interruption and migration.

Supported PowerMac 6100 L2 sizes?


The Apple Developer Notes doc for the 6100 indicates that 256 KB of L2 cache is the max:
All Power Macintosh models support secondary cache expansion to 256 KB
But this ancient 6100 upgrade guide suggests that someone at some point has uses 1 MB L2 cache with significant performance improvement in the range of 50-80% with the explanation:
There doesn't seem to be much incremental improvement from installing a 512 K cache, but there does seem to be a pretty significant boost from installing a 1 MB cache. The reason is because of the DRAM-based video system. With a 1 MB cache, the entire frame buffer can be cached, resulting in greatly improved scrolling and dragging performance.
This sounds almost too good to believe! Does anyone have experience with 1 MB of L2 cache in a 6100 or know conclusively if this is a valid configuration?

Side note: the PowerMac 6100 Upgrade Guide web page is a lovely time capsule of the early internet ❤️


Well-known member
It seems that this is something that can be done, although this link seems to be based on the same information that you have pointed to.
It also points to the difficulty of finding the 1MB Cache SIMM (What are the specs on that, I couldn't find them listed?)
I found the 1MB SIMMs listed here -> www.micromac.com, which seems to confirm the information, since they sell them. It is kind of an old-fashioned sales site. Has anyone bought there recently?
Last edited:


Well-known member
My 6100 is running 1MB cache. I haven't run video or CPU benchmarks to quantify the difference though.


Thanks for the vcfed link! The poster is in my exact situation.

Seems like the 1MB cache may be a rare unicorn. @ymk was it difficult for you to find? I guess I'll start with 256 kb and try out 1MB if I ever find it.


Well-known member
Seems like the 1MB cache may be a rare unicorn.
From looking the last few years for a cache for The PCI PM range, the 1 MB cache appears to be just that: a unicorn. A member sent me a PowerLogix 1MB cache, but something on it is faulty—doesn't even chime with it installed—so I was sadly unable to test it.

The largest I've found (for the 4400/StarMax) is 512k. The difference between it and the 256k isn't exactly cavernous, but almost any L2 will present a boost over a cacheless machine. If I had to guess, I'd say the 256 to 512 step is linear.

But again, that's not the piltdown man et al. architecture, and I don't have a 1 MB to compare on mine.

But don't give up :) one may turn up eventually.


Well-known member
NewerTech sold a 1MB cache for the X100 machines back when.

I bought one I found pretty cheap from a retailer. It didn't work, but the warranty was good. NewerTech replaced it with a working unit.

Of course, this was back in the 90s some time.

I'm not sure where the thing is right now. One of these days I hope to copy out the connections and chips.

I think Bunson (Bunsen?) has been looking for one for about 15 years.


Well-known member
Apparently Apple didn't sell them officially on non-WGS configurations but the 1MB caches would work in any of the x100 models. I have one in my Pioneer MPC-GX1 Limited (which is a factory overclocked 6100 board in an awesome case). I'd be more interested in finding one of the L2 cache modules used in some of the oddball late-model 5xxx/6xxx NuBus boards (same form factor as the x100 but x100 modules don't work in these machines, nor do the combo ROM/caches from earlier 5xxx/6xxx models).


Oh wow, I hadn't heard of the Pioneer MPC-GX1 Limited. Really awesome looking computer! I didn't realize there were NuBus era clones!


Well-known member
BTW, the Hardware Developer Note for the WGS9150 says that it shipped with either a 512KB or a 1 MB cache, IIRC.

It also says that the logic to support the cache is in the HMC (the memory controller chip) and the 6100/7100/8100/9150 all used the exact same chipset, except that the 9150 used the FAT AMIC, but in any case, the HMC chip is the same across the line. So the same cache support should be present in all models.

See the L2 cache section in the note:


  • workgroup_server_9150[1].pdf
    169.2 KB · Views: 1