Performa/LC 580 Overclock

[alxlab]

The Apple Fool overclocking page is a great resource for clock chipping and overclocking but there's some missing info. The Performa/LC 580 is incorrectly marked as not being overclockable/upgradable. This is not true though since the board is identical to the Performa/LC 630 so the same resistor mod to bring it up to 40Mhz will also work on the Performa/LC 580. The only difference between the two boards is the backplate. Just follow the LC 630 guide on The Apple Fool.

If you're wondering what the extra card is on one of the logic boards, it's the DOS card of the Performa 630 DOS Compatible I have. The mod doesn't seem to affect the DOS card.

 

[Garth Beagle]

Yup, the LC 580 is the same, with an extra RAM slot not necessarily found on all other P630 variants. I've been using my LC580 board in a Performa 6220CD case (it's original case crumbled). I put a full 040 CPU into it and left it as-is.

I did the same overclock on an extra P630 board I had, taking it to 40MHz, runs fine. I put heat sinks on both the CPU and video (Valkyrie) chip.

 

[alxlab]

Here's the Norton Utilities 3.1 640x480 8bit benchmarks:

 

[alxlab]

Here's the Norton Utilities 3.1 640x480 16bit benchmarks:

 

[alxlab]

Yeah would be nice if there was a benchmark app that could use the internet to upload results. Any particular reason you prefer Norton Utilities over others like Speedometer, Mac Bench, Apple Personal Diagnostic, etc?

 

[MacintoshLibrarian]

Nice ! I need to do this trick to me 580. I went ahead and put a Performa 6200 board in mine to get some PPC action. But 68k is always the best in my mind.

 

[alxlab]

Yeah I tend to gravitate more toward the 68k Macs as well. Full 68040@40Mhz is pretty nice

 

[nottomhanks]

Can we put a full 68040 (not LC version) in the 575 Mystic, and will the Apple IIe card work with that? Would the processor need a heat sink?

 

[nottomhanks]

Where can I buy a 68040 40Mhz processor?

 

[alxlab]

I think the better choice is a 6360 board, if I recall. Much faster CPU and RAM access. The 6200 will run 68k stuff the same or slower than the 580 board does.

Yeah the are incompatibilities though. I like playing The Dark Queen of Krynn and sound doesn't work on PPC.

 

[alxlab]

Where can I buy a 68040 40Mhz processor?

I bought from this seller and the chips sent were legit XC68040RC40M cpus:

https://www.ebay.ca/itm/383675636030

The fact that they aren't perfectly clean is a good sign to me since they are likely pulls. I'd be wary of chips that look supper clean with bright print on them. Chances are they were clean and rebadged which may are may not be what they claim it to be.

 

[alxlab]

Can we put a full 68040 (not LC version) in the 575 Mystic, and will the Apple IIe card work with that? Would the processor need a heat sink?

There's actually a project in the hardware section of the forum for a variable clock speed mod:

"Spicy O'clock" project has started

 

[alxlab]

Here's the Norton Utilities 3.1 640x480 8bit benchmarks:

View attachment 346View attachment 347View attachment 348
View attachment 349View attachment 350View attachment 351

If anyone was wondering why the hard drive benchmark is so much higher than the stock hard drive, it's because I'm using a 40GB Seagate Momentus 2.5" drive.

 

[nottomhanks]

There are sources online, but you have to be careful about remarked CPUs. It has become fairly common practice among scammers to sand down or blast off the surface of a chip, and relabel it for something it's not.

However, the CPUs are only VALIDATED for 25, 33, or 40mhz. They can often run at faster speeds (as evidenced with your LC475 overclocked from 25mhz to 33mhz). Really a 40MHz 68040 is only necessary if you want to go above 40MHz or you want it to say 40MHz on it. Most 33Mhz 68040 can overclock to 40Mhz.

Also, it's not just dropping in a faster CPU, the board needs oscillator revisions to run faster.

So the only benefit would be the built in FPU and if you wanted to realize that 40Mhz, you’d have to modify some resistors to take advantage of it?

 

[alxlab]

So the only benefit would be the built in FPU and if you wanted to realize that 40Mhz, you’d have to modify some resistors to take advantage of it?

Yes exactly. Need to move a couple resistors. There are two revisions of the board that place the resistors in a different place. As extracted from the source page:

Note: there are two versions of this board.
The Rev A board is marked 820-0624-A on the top of the board in the corner next to the LC PDS slot, and on the bottom of the board on the opposide side from the SIMM slot. R149, R153, and R155 are on top of the board, and R156 is on the bottom.

The Rev B board is marked 820-0548-B on the top of the board in the corner next to the LC PDS slot, and on the bottom of the board on the opposide side from the SIMM slot. All four resistors are on the bottom of the board.
Here are some Rev A motherboard shots thanks to Ross ([email protected])

Top of the board:

Zoom in of the top of the board:

Bottom of the board:

Zoom in of the bottom of the board: