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LC 575 L2 cache card

Posted by: jasa1063 on 2021-07-29 18:59:40

I just got a Mac Color Classic with the Mystic LC 575 motherboard upgrade. I was wondering what L2 cache cards would work with the LC 575 motherboard? If so, are any readily available?

Posted by: trag on 2021-07-29 19:28:02

I may be completely wrong....

But I think any cache card in the LC575 would have to go in the LC-style expansion slot, and because of the compromises made to keep it compatible with the original LC slot, I suspect performance would not be very good. There might have been a cache that plugs in between the 68040 and the socket.

Point is, I don't think there was a cache for that line. But again, happy to be proven wrong.

Posted by: jessenator on 2021-07-29 20:03:37

Sonnet's QuadDoubler was only for Centris/Quadra machines, and I don't think that included the 605 (LC 475). Per a Wayback Machine view of the product page, was only these models:

For the Centris 610, 650 & 660AV; Quadra 610, 660AV, 700 & 900; and Workgroup Server 60/20 & 60/25.

I'm sure that the more esoteric manufacturers weren't making much, either. Even MicroMac only ever had a full 68040 for the LC 575, or an LC 575 board upgrade for the Color Classic—both of these listed as 'upgrades' on their site... heh

I'm with trag on this one. Here's a quote from the LC 575 Developer Note:

expansion slot for 96-pin or 114-pin expansion cards (accepts PDS cards designed for the Macintosh LC series; not directly connected to the MC68LC040 processor)

And further into the manual:

IMPORTANT The expansion slot is not a PDS because it does not connect directly to the computer’s MC68LC040 microprocessor. The expansion slot supports cards designed to work with the MC68030 microprocessor

It sounds to me that no L2 cache could be constructed to be slotted into the LCPDS , as its interface is not designed in any way like the Centris/Quadra PDS slot. So, things like ethernet and other expansion cards could work.

Edit: I suppose that something could be designed to simply (hah!) stack, like the QuadDoubler, into the 68040 socket with the CPU on top. But there might be further eccentricities in the board design that may prevent something like this from working.

So nothing turnkey, I'm afraid.

Posted by: jasa1063 on 2021-07-30 15:53:15

My whole reason for asking was I came across this post from lowendmac.com: It mentions there was a supplier for an adhoc L2 Cache Card for the LC 575, but the post is from way back 1998.

Level 2 Cache for the 68040 - Low End Mac

A Level 2 (L2) cache was a popular way to boost performance on faster 68030-based Macs, including the Mac IIci, Mac IIvx, and Mac IIfx. But none of the 68040-based Macs shipped with an L2 cache, although most were capable of using one. The L2 cache is automatically accessed by the 68040 series...

lowendmac.com

Posted by: jessenator on 2021-07-30 17:32:55

I'm not sure if these ever came to market, if they were even produced. I'm betting less than 20 were ever made. I mean, if they still exist and you can find them, more power to you! Not trying to be belligerent about it, just real.

I found this other report that there isn't a way to get the case closed again, in the case of the 475, and that makes me wonder about the clearances inside of a 575 or CC, but it might be a different configuration.

Incidentally, the QuadDoubler Cache variant mentioned is real; a member posted theirs in a thread on recreation of the QuadDoubler (with cache I believe). Though the Newer Technology one mentioned in that other note seems very interesting...

Sonnet Quaddoubler project

Looking for a Quaddoubler at a decent price...now here is the caveat. I want to destroy it.......in the interest of reverse engineering one and then being able to get them at a decent price. Many cards have been reversed engineered in Amiga land and this would be a very beneficial one for...

68kmla.org

It all comes down to the orientation of the CPU slot and clearance. Not sure if anyone's thought about making an adapter, as you'd be adding a lot of height with each rotation/reconfiguration of the pinouts. But I'm not the hardware recreation expert 🙂

Posted by: jasa1063 on 2021-07-30 17:39:23

I'm not sure if these ever came to market, if they were even produced. I'm betting less than 20 were ever made. I mean, if they still exist and you can find them, more power to you! Not trying to be belligerent about it, just real.

I found this other report that there isn't a way to get the case closed again, in the case of the 475, and that makes me wonder about the clearances inside of a 575 or CC, but it might be a different configuration.

Incidentally, the QuadDoubler Cache variant mentioned is real; a member posted theirs in a thread on recreation of the QuadDoubler (with cache I believe). Though the Newer Technology one mentioned in that other note seems very interesting...

Sonnet Quaddoubler project

Looking for a Quaddoubler at a decent price...now here is the caveat. I want to destroy it.......in the interest of reverse engineering one and then being able to get them at a decent price. Many cards have been reversed engineered in Amiga land and this would be a very beneficial one for...

68kmla.org

It all comes down to the orientation of the CPU slot and clearance. Not sure if anyone's thought about making an adapter, as you'd be adding a lot of height with each rotation/reconfiguration of the pinouts. But I'm not the hardware recreation expert 🙂

Thanks for your input and I knew it was a long shot anyway. I did replace 68LC040 with a 68040 as I do have some floating point intensive software I run for Fractals and Ray Tracing,🙂