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Level 2 Cache for the 68040

Scott L. Barber

Scott L. Barber first posted this to Quadlist. It is reprinted with his permission.

The Level 2 (L2) cache is accessed by the 68040 series processor, whether LC040 or full 040. When Motorola designed the chip, it was designed to look for L2 cache when the power came on, so there usually isn't a control panel or software addition to use the L2 cache. This is especially true with the no slot solutions where the L2 cache consists of a small daughtercard that plugs into the processor socket, and then the existing processor plugs into the daughtercard. A further variation of this was the QuadDoubler 128k, which had both 128k of L2 cache and a 4x clocked processor.

Given this, the only limitation to getting a L2 cache into your machine is how the acreage on the motherboard is divided. Since each motherboard design may move or relocate the 040 socket to a different spot on the motherboard, making a no-slot cache solution may mean making sure that the cache card does not hit the case wall, or block expansion slots. In addition, enough case height must exist so that the card can be installed, and the lid still put on the machine.

Because of the various designs of the 040 motherboards that Apple released, there would be necessary 4 cache cards to be made that would adequately fit all of the motherboards available, with a few exceptions. This is an ad hoc list of those that I know exist. Note that Quadra/Centris/Performa is the same thing on this list, so there aren't any further questions about the matter

Q610/660AV
Q650
LC475/605/LC575*
Q700 Q800 Q9xx

* LC575 is the only model that has trouble - I have a supplier that has ad hoc 575 cache cards - please contact me directly if you're interested in this option.

Please note, I have not found a cache card for either the 630 or 640. Don't ask. If I find a supplier that will meet the constraining needs of these two motherboard classes, I will of course announce it on the list. As well, if the above list does not match your form factor, then I haven't seen one. The list above is as complete as I'm aware of. I don't know of any other machines but the ones on the list above. There is no need to ask me if your machine is supported if it's not on the list, because I haven't found one that works with it, whatever the model.

Scott L. Barber <serker@earthling.net>

Pres/CEO, SERKER Worldwide, Inc.

Providing Hardware/Networking/Telecomm for 13 years

Quadlist, the listserv for users of 68040-based Macs. FAQ at <http://lowendmac.com/lists/quadlist.shtml>

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