Mac IIci & cache card questions

[Bolkonskij]

Hi everyone,

so, we have been using my beloved Mac IIci (dream machine of my youth; dad instead brought home a LC). I’ve heard the IIci does very well with a cache card installed. Unfortunately mine didn’t come with one.

I’ve seen ads of manufacturers claiming a 30-40% speed increase. Now we all know these ads (…). Anyone got a cache card in his IIci and would give me his/her hopelessly subjective opinion - is it worth the trouble finding a cache card? Is there really a noticeable speed gain? If so, is that gain application dependent or a general better performance?

I remember reading somewhere that the original Apple cache card from 1990 is to be avoided as it had a faulty chip that would lead to crashes. Right or is my memory serving me wrong? If so, which alternatives would you recommend?

Also, what’s the best place to find one of these cards today? I’m located in Germany. eBay turned up an Apple cache card in the U.S. and that is it. Any dealers that still sell that kind of stuff?

 

[Kai Robinson]

I've seen loads available on eBay - pretty cheaply, too. They are a nice performance boost, but for actual percentages, someone with a IIci might be better off telling you

 

[ktkm]

I would say the original ’Macintosh IIci Cache’ gives a performance increase with approximately 25%. I haven’t experienced any crashes in particular, and since they are pretty easy to come by, I would certainly go for one if I were you.

 

[Mr SN]

Anyone got a cache card in his IIci and would give me his/her hopelessly subjective opinion - is it worth the trouble finding a cache card? Is there really a noticeable speed gain? If so, is that gain application dependent or a general better performance?

I got my first IIci in 1990 and it was about a year before I got a cache card. Having used the Mac daily, I could tell the difference the card provided, which varied by application.  The other thing that can help a mac feel faster is a video card, especially an accelerated one.  That way the mac isn't using onboard RAM for video RAM.  Combine the cache card with a good video card and the mac (back then) felt quite snappy.  

Today, since we're mostly using the mac for nostalgic reasons, the gain you get from either of those is really more for sentimental reasons than productivity reasons.  

I agree with ktkm's comment, the cache card does give overall about a 25% boost in performance.  I'd say if you can get one for a reasonable price (under $30), go for it. 

 

[Unknown_K]

There were other cache cards available for the IIci. I have one that has 128KB cache on it (apples was 32KB).

I was kind of wondering what Apple never bothered with cache on the 68040 Quadras since it does help quite a bit and it was cheap to do.

 

[Mr SN]

Since we're talking the IIcis, here's a fun tidbit.  An easter egg exists in the IIci ROM (I seem to recall that many 68k macs had easter eggs). If the system date is set to September 20, 1989 (the machine's release date) and the ⌘ Command+⌥ Option+C+I keys are held during boot time, an image of the development team will be displayed.

 

[Mr SN]

There were other cache cards available for the IIci. I have one that has 128KB cache on it (apples was 32KB)

I remember waiting for 3rd party vendors to offer cache cards and I got one of the 128k ones as well.  I can't recall what I paid, but I do recall it was cheaper than apple's and had more RAM. Here's mine below, I bought it from a vendor in the back of Macweek.

 

[elbaroni]

There were other cache cards available for the IIci. I have one that has 128KB cache on it (apples was 32KB).

I was kind of wondering what Apple never bothered with cache on the 68040 Quadras since it does help quite a bit and it was cheap to do.

Didn’t the 040 have built-in cache?

 

[Unknown_K]

Didn’t the 040 have built-in cache?

From my understanding none of the 040's had motherboard cache and it makes a big difference.

 

[trag]

From my understanding none of the 040's had motherboard cache and it makes a big difference.

The 68040 has 4KB data and instruction caches on board (L1).  The 68030 had only 256bytes each, or 1/16 as much L1 cache.   Apple may have felt that there was little need for an L2 cache with such a large L1 cache already present.

Did anyone ever manage to source the Quadra cache slot connectors?  It would be interesting to take some modern SRAM and see what a Quadra might do with something like a 4MB L2 cache running at CPU speed.

 

[dr.diesel]

Did anyone ever manage to source the Quadra cache slot connectors?  It would be interesting to take some modern SRAM and see what a Quadra might do with something like a 4MB L2 cache running at CPU speed.

The standard Motorola 040 datasheet doesn't mention or outline how an external cache is wired/configured.  Anyone have any such documentation?  I had thoughts of making a CPU socket card for my Q605.

 

[trag]

There are some detailed notes in one of the Apple books.  Either Cards and Drivers or Family Hardware.  Not detailed enough to actually build a card...    One will also need to understand the 680x0 bus and how transactions are conducted and how they can be interrupted.   There might have been a Motorola tech note floating around too.   I can't remember.

The IIci uses a bunch of extra circuitry to manage the cache and essentially take over the address/data busses.   On Power PC either the CPU or the memory controller has more cache friendly capability built in -- probably the Apple memory controller as all those machines had dedicated cache slots.   On the NuBus PPC, there's no need for any logic.  Just supply Cache RAM and Tag RAM in proper quantities, wired to appropriate pins.    On the PCI PPC it looks like Tag RAM is no longer needed, subsititure regular SRAM for the TAG SRAM.   I guess the comparators were moved to the memory controller.

But on the 680x0 you'll need some kind of CPLD to manage the 680x0 bus.

I'm not sure about the Quadras, but the IIci has 8MB of address space allocated to cache, which would presumably be, 4MB of cache and 4MB of Tag.    It would be interesting to roll up a 4MB cache for the IIci and see what happens.  

 

[Unknown_K]

Well the Newer Tech Quadra overdrive with cache seems to befaster then the non cache version and its not an expensive upgrade.

 

[dr.diesel]

But on the 680x0 you'll need some kind of CPLD to manage the 680x0 bus.

Yeah that takes all the fun out of it.

MicroMac shows a CPU socket Quadra cache card, only 128k, I suspect they were quite rare as I've never even heard of one out in the wild.

https://www.micromac.com/products/quadra_cache_cards.html

 

[jessenator]

MicroMac shows a CPU socket Quadra cache card, only 128k, I suspect they were quite rare as I've never even heard of one out in the wild.

Is that how the the "slot-free" version works? I suspect their non-slot-free card ( DayStar equivalent pictured in this catalog) blocks the nubus slot in-line with the cache/PDS slot...

Did anyone ever manage to source the Quadra cache slot connectors? 

I found this in an Apple Developer Notes PDF... Is this helpful at all?

The PDS connector is a 140-pin connector manufactured by KEL  Connectors, Incorporated. The connector on the main circuit board is KEL part number 8817-140-170SH; the corresponding connector on the PDS card is part number 8807-140-170LH.

I did a quick search and KEL doesn't have active inventory numbers for the part. I'm sure someone could find them someplace... I'm sure there are offline places to search, but I have no clue.

 

[Mr SN]

4MB of cache and 4MB of Tag.

That is a crazy amount of cache for a system of that vintage. And there are diminishing returns the larger the cache gets.  

 

[Unknown_K]

That is a crazy amount of cache for a system of that vintage. And there are diminishing returns the larger the cache gets.  

Not if the whole program fits in cache.

 

[Bolle]

( DayStar equivalent pictured in this catalog)

Here's a shot of the actual thing:



There's some logic on there to decode DRAM accesses to write cacheable data to the cache accordingly and interrupt the CPU DRAM read cycles on a cache hit and supply the data before the DRAM could do.

040-socket cache cards basically would have to do the same.

 

[jessenator]

Nice  

I guess you could theoretically get a short NuBus card in that slot at the same time.



So if someone can source KEL 8807-140-170LH connectors, new cards would be probable.

I don't have the resources to test it myself on 68k machines, but on my PowerPC Macs I've had a small amount of L2 cache to do small testing with. I've noticed (with MacBench) decent boost with no cache vs 256k L2 cache, and then what appears to be a linear gain going up to 512k. I can't prove that, since I don't have a working 1MB cache or anything higher.

It would be interesting if you had like a variable cache card: PLCC sockets for the RAM. No idea if you could build logic chips around that kind of arrangement, but fun to speculate.