Folks,
@Mr. Fahrenheit very kindly alerted me to a very surprising discussion at the other forum which introduces a groundbreaking discovery by Mustermann. Apparently, you can now overclock an LC 475, CC Mystic and other machines by software alone, without even using Spicy O'Clock, from @Kay K.M.Mods (Kero's Mac Mods). Here's a screenshot of the machine compatibility from the installer app:



When you download the software overclocker BIN file (created by Phipli) and then put it on your vintage Mac and use Stuffit Expander to decompress it, the installer app will look like this:



It installs a Control Panel and an Extension:


No mention is made of software compatibility, but most likely it works on System 7.1 through 7.5.5. (I made these screenshots in Basilisk II booted into System 7.5.5.)

Once installed, you can set the clock speed in the Control Panel (which then requires a restart):



There's even a "Custom" selection in the popup menu that allows you to see higher clock frequencies:



If you try a clock speed too high for your Mac and it freezes, just reboot with SHIFT held down to prevent the CP and Ext. from loading. This and more is described in the installer app's README text. So be sure to read that completely before installing it.

It's not clear if VRAM speed is as important as it is when you overclock with Spicy, but I suspect it is. Having a 68040 with full FPU will also impact your performance and probably overclockability too. Heatsinking at high clock speeds is still important.

Another thing that is not clear is how serial ports and SCSI are impacted. In my own testing of Spicy, serial ports stop working when the CPU is overclocked higher than 43.48MHz. (I confirmed serial ports don't work at 43.7MHz when using Spicy.)

DISCLAIMER: I've not tested this software overclocker on my Color Classic Mystic yet (which still has Spicy O'Clock installed).

@Mr. Fahrenheit has tested it though and confirmed it overclocked his CC Mystic to 40MHz. It's not clear if he tested clock speeds higher than that.

The great thing about this solution is that (1) there's nothing to buy to try it, and (2) you just reboot with SHIFT held down if you overclock too high.

Have fun!

P.S. If you find it useful, I recommend sending a word of thanks to Mustermann and Phipli at the other forum, as well as thank Mr. Fahrenheit for his testing and involvement.

As someone who has done the "hardware" overclock on my 475, I also moved a resistor to keep the SCSI controller at 25MHz (R96 to R95 - see photo). Is there any indication whether or not a software overclock would affect SCSI? I have seen file transfers cause lock ups, reportedly caused by SCSI controller instability at higher frequencies.

@Garrett
Because I have not yet done the software overclock, and because I don't own a 475, I'm not equipped to answer your question.

However, I keyword-searched all pages in the other forum's thread for "SCSI" and I found the following post from @Bolle :

I did some testing with this a little while back and didn't run into any issues using a BlueSCSI v2 off the internal SCSI bus.

I was able to overclock a Quadra 605 with its stock 25MHz CPU and a LC 475 which had already been HW overclocked to 33MHz.

Both ran ok at 40MHz, the highest it'd set to was 43MHz. Anything higher and it just didn't seem to take the change.

Here's some CPU benchmarks at various speeds on the Quadra 605.

The real question is whether this has an impact on service lifetime and/or burns those systems out sooner.

>> Garth Beagle said:

I did some testing with this a little while back Click to expand...

Really? The code was only released this month. Have you been doing your own hacks? Could you share your code?

>> JDW said:

No mention is made of software compatibility, but most likely it works on System 7.1 through 7.5.5. (I made these screenshots in Basilisk II booted into System 7.5.5.) Click to expand...

The control panel is probably 7.5 to 8.1 (and later with a PPC upgrade). I wrote the CP in RealBasic, so I suspect it wont run in 7.1 (probably will with Finder 7.1.3 installed in 7.1 though - that adds most of the things you need - Finder 7.1.3 came with System 7 Pro and 7.1.2 if you're looking for a copy - you'll then need to install AppleScript probably). The Extension will work in any OS that the 475 family machines will run, and the speed could be changed in another OS and then copied over, or you can edit it with ResEdit.

>> JDW said:

It's not clear if VRAM speed is as important as it is when you overclock with Spicy, but I suspect it is. Click to expand...

This setup should overclock more than the Spicy wrt RAM, ROM and VRAM timings (as well as serial and floppy drive I believe), because the code also changes the number of wait states to the correct level for 40MHz. This isn't possible usually with a 475 or 575.

>> JDW said:

Another thing that is not clear is how serial ports and SCSI are impacted. Click to expand...

SCSI clock mod to divide by two should be done to ensure best SCSI reliability. What is it... swapping R96 to R95 on the 475? Should already be done on the 575 from factory. Some people seem to have good luck without needing to do this... but if you're going for records, you'll want to do the mod.

My 475 has the upgraded 80MHz clock divider part (88916DW80??), the SCSI clock mod and a 40MHz grade CPU with a heat sink.

I've got a reliable 50MHz at the moment, RAM is likely my limit as the soldered RAM is 80ns. Even at 40MHz with 40MHz timings I should have 70ns RAM, so it is a significant overclock on the soldered RAM. I'm not going to be pushing faster any time soon becaues when I have time I want to get back to improving the software and implement Mustermann's latest tweaks. I've managed to run a CPU benchmark at 55MHz, but it crashed while doing the video benchmark (I only have 70ns VRAM). At 60MHz it crashed instantly.

>> Garrett said:

Is there any indication whether or not a software overclock would affect SCSI? Click to expand...

It physically increases the bus clock, identically to changing the resistors. The benefit is that it can also change the number of wait states to 40MHz settings, so improves the behavior of subsystems that need that (you're using 40MHz timings instead of 25 or 33MHz - the 475 ROM doesn't support 40MHz sadly (unlike the 650). Best to do the SCSI clock speed resistor mod as you've pointed out.

>> JDW said:

following post from @Bolle Click to expand...

The 161 vs 135 thing isn't to do with SCSI, that is to do with which type of clock generator (the part we're manipulating to change the CPU clock) is fitted. There were two types, at least two part numbers.

>> ClassicHasClass said:

The real question is whether this has an impact on service lifetime and/or burns those systems out sooner. Click to expand...

The boards were spec'd to 40MHz at design, as was the chipset for the most part. Things that might struggle at 40 are possibly the 88920, VRAM, RAM and the CPU. There is a resistor connected to the CPU that might need to be set to different values depending on the system clock, but I've never bothered changing it, and wouldn't be confident about the values in the schematic anyway as Apple never shipped 40MHz machines.

@phipli
Incredibly informative and helpful post, thank you! And kudos to you on the amazing work you've done in bringing Mustermann's overclocking work to the masses. [clap]

>> phipli said:

Really? The code was only released this month. Have you been doing your own hacks? Could you share your code? Click to expand...

I used your build you'd attached in the comments to your video.

Made an updated version. Mustermann found my bug that was stopping arbitrary speeds working on all machines (not sure arbitrary speeds were working on any to be honest...).


This version now fully works and you can type in absolutely any speed you like, for example, if you really want to run your LC 475, 575 or similar computer at 27.85MHz, you can (although things like Clockometer aren't that accurate anyway).

Note I haven't put an upper or lower bound on speeds you can pick, so it is up to you to find the upper and lower limits of your machine. If you have problems, remember, power off with the switch, power back on holding shift to disable extensions, then launch the Control Panel and select a safe speed before restarting. Nothing is permanently changed on the computer, it is all software.



WARNING! Do not run this software if you have replaced the stock speed resistors with blobs of solder. Although you really shouldn't have done that in the first place, and I'm not sure that anyone would have. Just thought I might say this in case someone had. Actually, I really should say not just "don't use this software", but "go and put resistors back", if you haven't got any, I'll send you some. You shouldn't have shorts instead of resistors xD

What affect will this software have on a machine which has had the 33 MHz resistor move modification? Do the resistors need to go back to their original positions?

Edit: Never mind. Found the answer here: https://68kmla.org/bb/index.php?thr...-soldering-or-spicy-o-clock.47946/post-538497

It looks like the resistor move just affects the start up speed, unless I didn't read far enough adn there was later correction.

>> trag said:

What affect will this software have on a machine which has had the 33 MHz resistor move modification? Do the resistors need to go back to their original positions? Edit: Never mind. Found the answer here: https://68kmla.org/bb/index.php?thr...-soldering-or-spicy-o-clock.47946/post-538497 It looks like the resistor move just affects the start up speed, unless I didn't read far enough adn there was later correction. Click to expand...

As long as you fitted appropriate resistors for 33MHz you're fine :)



The schematic values match the Apple Fool clock chipping website, so if you followed either you're good. I actually fitted a 320 to mine because I misplaced the original 300R - I'm not too bothered about 20 ohm higher (its a right side error), although I since found some 300R parts in my parts bin.

I actually reverted my 475 to the stock 25MHz during the project because I wanted to work from stock in that sense. Interestingly the 575 (which is the same chipset on a different board layout) came stock as 33MHz.

@phipli
I believe your app not only works on the LC575 motherboard too, but it will work even if the CPU has been overclocked with Kay Koba's Spicy O'Clock too, correct?

>> JDW said:

@phipli I believe your app not only works on the LC575 motherboard too, but it will work even if the CPU has been overclocked with Kay Koba's Spicy O'Clock too, correct? Click to expand...

It wont work if you have a Spicy O'Clock installed because you have disconnected the onboard clock generator that we are re-programming. The RAM timings should still take though, so it might help out the Spicy O'Clock.

The clock generator goes way higher than the computer could ever achieve though, so there wouldn't be a benefit in using the Spicy O'Clock. Especially once I add on the fly speed changes and separate speeds for PPC and 040. Likely the latter before the former.

Tum te tum...

Today's progress :


Its less far on than it looks. I was just testing after building the XCMD I'm using to set the clock speed. Absolutely flabbergasted that it worked first time. I literally only compiled it (successfully) once.

The app itself isn't function complete yet. The current speed thing at the top is just showing the raw ms timings for my sudo-benchmark and I haven't written the stuff to read and write from the extension yet.

This is great!

Looking forward to a newer release so I can give it a go on my stack of LC/Performa 475 and Quadra 605 Macs :D

>> Garth Beagle said:

This is great! Looking forward to a newer release so I can give it a go on my stack of LC/Performa 475 and Quadra 605 Macs Click to expand...

First pass is mostly done, I had to stop for dinner earlier. The built in speed estimation thing needs a little calibration tweak and I need to make it load in the current settings from the extension on launch... after than I just need to do some testing to make sure everything works.

I don't have a PPC upgrade for my LC 475 - does anyone here have one? Anyone with a little bit of time to test the PPC functionality before I share the updated version? I can write a short list of stuff to test so you don't have to spend long at it. I'm talking about these things (Specifically the 66MHz version) :


(picture from https://wiki.preterhuman.net/DayStar_PowerCard_601)

>> phipli said:

I don't have a PPC upgrade for my LC 475 - does anyone here have one? Click to expand...

Hopefully someone helps you out, because these prices are insane!

>> phipli said:

I've got a reliable 50MHz at the moment , RAM is likely my limit as the soldered RAM is 80ns. Even at 40MHz with 40MHz timings I should have 70ns RAM, so it is a significant overclock on the soldered RAM. I'm not going to be pushing faster any time soon becaues when I have time I want to get back to improving the software and implement Mustermann's latest tweaks. I've managed to run a CPU benchmark at 55MHz, but it crashed while doing the video benchmark (I only have 70ns VRAM). At 60MHz it crashed instantly. Click to expand...

At what clock speed did your serial ports stop working?

With Spicy O'Clock (which doesn't overclock everything your app does), serial ports stop working when the CPU is overclocked higher than 43.7MHz.

>> phipli said:

First pass is mostly done, I had to stop for dinner earlier. The built in speed estimation thing needs a little calibration tweak and I need to make it load in the current settings from the extension on launch... after than I just need to do some testing to make sure everything works. I don't have a PPC upgrade for my LC 475 - does anyone here have one? Anyone with a little bit of time to test the PPC functionality before I share the updated version? I can write a short list of stuff to test so you don't have to spend long at it. I'm talking about these things ( Specifically the 66MHz version ) : View attachment 18135 (picture from https://wiki.preterhuman.net/DayStar_PowerCard_601 ) Click to expand...

I have mine still, but I've not touched it in years. I might be able to dig it out and set it up at the weekend but my office is a dump right now with limited space.

>> phunguss said:

Hopefully someone helps you out, because these prices are insane! Click to expand...

Thankfully I don't think that price is anything more than optimistic on the seller's part. We all have number keys and can mash them randomly. Never take listing prices as an item's value - always look at completed. There aren't any showing atm, but last time I saw they were selling in the $400 to $500 range ignoring outliers. Even at that price they are already more expensive than they should be, given for a colour classic, you could just modify a Performa 6400 or 6500 board to fit the chassis, and for an LC 475... well, I'd just buy a 6360 or a 6100 if I wanted more performance from a small mac. Sure, it isn't quite the same thing, but I'm not paying $900 extra for a slightly different case. You can have fun with any mac, you don't need something RARE.

>> JDW said:

At what clock speed did your serial ports stop working? With Spicy O'Clock (which doesn't overclock everything your app does), serial ports stop working when the CPU is overclocked higher than 43.7MHz . Click to expand...

I haven't tested serial yet - I don't tend to use the ports much. I'll have a look at some point, but want to finish the programming first.

>> Kai Robinson said:

I have mine still, but I've not touched it in years. I might be able to dig it out and set it up at the weekend but my office is a dump right now with limited space. Click to expand...

Thanks Kai, give me a ping on Discord when you're setting up. I'll be about Saturday but we have guests on Sunday. I can ping you a test spec though regardless.

Is it a 66 or a 100?