"475 Overclock" control strip on Color Classic Mystic - problems and solutions

[Marconelly]

I watched @JDW video on this, and immediately rushed to try the "475 Overclock" Control Strip on my Color Classic Mystic. At first, it didn't work no matter what I tried. The latest 475 Overclock 1.0.4 didn't work on either System 7.6.1 or 8.1. Neither did the older 1.03 version of 475 Overclock. Anytime I would do a clock change it would just beep (which means there is a problem), and the Clockometer was not showing any change

Thankfully in his video, JDW mentioned he used "Wish I Were..." control panel, which allowed him to try some clock speeds with better success. So I got the "Wish I Were" and set my Mystic to report itself as LC 575. After that, 475 Overclock worked without an issue! I'm not sure why I needed to do this? Shouldn't a logic board taken out of LC575 report itself as 575, without needing to fake this?

Something else that was really interesting is that when reporting itself as LC575, my Color Classic worked great when setting the clock speed to 40MHz, but would freeze if I set the clock at 45MHz. However, when I changed the "Wish I Were" to report my computer as LC475, I could use 45MHz clock speed just fine! This actually seems to mirror JDW's experience where he could only stably use 50MHz clock if setting Wish I Were to report as LC475.

With 45MHz speed (and even with 40Hz() I could really feel the difference. Even regular OS actions like the windows opening and closing felt snappier, and the MAME emulator that struggled to run anything at full speed was very noticeably improved. It's a nearly 40% speed increase after all!

Now that I got this working, I do have a few questions:
- Is it normal that I need to use Wish I Were to get the Overclock control strip to work at all?
- Is there some danger in leaving Wish I Were to permanently report my computer as LC475?
- Should I buy a 60ns RAM for this Color Classic, and if so, where should I get it from? How can I tell if I already have 60ns RAM inside? I've already recapped the board with OS-CON capacitors which should provide greater stability with overclocking.

 

[Nitram78]

Another member and I had the same problem a few weeks ago, see here.

The fact that a lot of information about the Mystic modification of the Color Classic is scattered and sometimes even lost (even though more or less retrievable via the Wayback Machine) is a difficulty in itself, which means we can miss out on vital information.

I did watch JDW's video when it first came out, but I hadn't picked up on the hint he gave about what we're interested in here. It could have saved me a lot of time.

 

[JDW]

I’m tagging @phipli because he might have some ideas.

I myself and am very surprised to hear that you would need to use WISH I WERE on an LC575 motherboard to let 475 OC know it’s a 575! That’s just plain weird! There’s no harm in using the software like that though.

But in answer to your question about RAM, I think you may have been wanting to type VRAM instead, correct? Yes, absolutely buy 60ns VRAM! it makes a huge difference.

But in terms of the RAM SIMM, you need to check the markings on your motherboard’s soldered RAM because if those chips are 70 ns, then buying a RAM SIMM that’s faster than 70 ns really wouldn’t have much meaning. If you’re soldered RAM chips show 60 ns, then you should be using a 60 ns or faster RAM SIMM.

Some people have even suggested desoldering all of the RAM from the motherboard, and then use a super fast RAM SIMM. But I think that’s a little extreme, especially when I can overclock do some pretty high speeds without doing that.

That’s about all I can say for now. Hopefully, @phipli can add his thoughts.

 

[Marconelly]

I did watch JDW's video when it first came out, but I hadn't picked up on the hint he gave about what we're interested in here. It could have saved me a lot of time.

I too suspected the VGA mod is why @JDW didn't have this issue (like you, I also changed the System resource to make the machine boot correctly) - glad to see you confirmed it, and got it working!

I myself and am very surprised to hear that you would need to use WISH I WERE on an LC575 motherboard to let 475 OC know it’s a 575! That’s just plain weird! There’s no harm in using the software like that though.

But in answer to your question about RAM, I think you may have been wanting to type VRAM instead, correct? Yes, absolutely buy 60ns VRAM! it makes a huge difference.

I guess the reason was the modification in the system resource files I did to make the LC575 board work in 512x384 resolution. So you think it's OK even if I leave "Wish I Were" to report my computer as LC475 (because that way I get more stable 45MHz overclock)?

Yes, I meant the 60ns VRAM Not sure where I should get it - is the "Purple RAM" a good choice?
I think I would need this one, right: https://www.tindie.com/products/jurassicomp/low-latency-60ns-512kb-68-pin-vram-simm-macintosh/
How can I tell if I already have the 60ns VRAM though? Mine already has 2x 512K VRAM SIMMs, but it was updated back in the 90s by its original owner.

 

[JDW]

Wait…
Has SiliconInsider (Dr. Antoine Bercovici) changed his business name to Jurassic Computing? Because those are his products, and yet I’ve never heard of Jurassic Computing.

if indeed, those are being sold by SiliconInsider, then they will work fine. And I must say, I’m a fan of his gold plated stuff.

But 60ns VRAM for the Mystic is sold by other vendors as well, including @Kay K.M.Mods here:

SMC VRAM 512KB 60Ns for 68040 Overclocking/ 2 pcs per set | infinityproducts

SMC has engineered an entirely new VRAM SIMM for vintage Macs. This new, low latency 60ns design allows you to take CPU overclocking to an all new level! Version historyRev V.1.0(2022/02/04): Alexandre Marcoux redesigned it into two layers based on Zane Kaminski's original design. Drake added...

en.infinityproducts.co.jp

There are other 60ns VRAM vendors as well. I just don’t have time right now to Google them all.

And as to identifying what speed VRAM you have right now, I would recommend shooting a clear photo of the markings on the chips and uploading that to this thread.

LASTLY…

I honestly never thought that NOT having the VGA mod on a Mystic would create trouble for 475 Overclock. It would be good to have at least one other person confirm that same problem, so then @phipli could possibly update his 475 OC Blog page about that. But no, there shouldn’t be any harm to using Wish I Were all the time.

 

[Nitram78]

@Marconelly, can you check which machine ID is detected when Wish-I-Were is not active? Using Tattletech for instance.
In my case, the motherboard identified is an LC580. Obviously because of the System patches.

 

[Marconelly]

@Marconelly, can you check which machine ID is detected when Wish-I-Were is not active? Using Tattletech for instance.
In my case, the motherboard identified is an LC580. Obviously because of the System patches.

Yes, I can confirm that Tattletech is reporting the same for me:
Mac LC 580 | Performa 58X (99)

And as to identifying what speed VRAM you have right now, I would recommend shooting a clear photo of the markings on the chips and uploading that to this thread.

Here it is. These sticks are actually Apple branded, and dated 1991:

 

[JDW]

The -8 at the end shows they are the slow 80ns type, which is typical for stock VRAM in the LC575.

To get the most out of either Kay Koba's Spicy O'Clock or 475 OverClock, you need faster VRAM. Yes, there are the lazy folk who make due with slower overclocks because they don't want to buy faster VRAM, but I'd advise to avoid that mentality and just get the 60ns VRAM so you can remove that bottleneck and potentially have more fun. For me, it's not about 40MHz or 45MHz being "fast enough" but rather a matter of "how fast can this machine go!" Now, there's a difference between the fastest clockable speed and one that is stable for hours on end, but for the most part, I can reach 47MHz just fine and still boot into any compatible OS. I can even go to 49MHz and boot just fine into System 7.1 (ignoring 7.61 and OS 8.1). And for short periods, I can even use 50MHz. None of that fun would be possible with VRAM slower than 60ns.

Now, I have heard at least one person tell me (I think it was @phipli) who said they could reach 50MHz speeds without the need to use OS CON capacitors in their recap. But if memory serves me correctly, he has a 475, not a 575 like I do. When Kay Koba had solid tantalum caps on his 575, he wasn't able to reach 50MHz speeds. I then came along and decided to use lower ESR OS CON caps on my 575 motherboard and I was able to reach 50MHz. I told Kay about that, then he replaced his solid tantalums with OS CON, and then he too (with the aid of fast VRAM) was able to reach 50MHz. So all this means is that if 60ns VRAM alone doesn't get you to higher clocks, you need to consider the capacitors on the motherboard.

Of course, not every 040 is able to overclock to 50MHz, especially the ones made for 25MHz operation. But in my testing I found that the LC edition 040's, without any FPU, tend to overclock lower than the 040's with an FPU. Maybe that's a fluke in my testing, but I can't test anything outside what I own. I'm just reporting it. And the higher the clock rating of the 040 processor, the more likely you will be to hit 50MHz in your overclocks.

Then you need to heatsink and possibly fan to ensure you can maintain your overclocks.

Hope this helps!

 

[Marconelly]

The -8 at the end shows they are the slow 80ns type, which is typical for stock VRAM in the LC575.

To get the most out of either Kay Koba's Spicy O'Clock or 475 OverClock, you need faster VRAM. Yes, there are the lazy folk who make due with slower overclocks because they don't want to buy faster VRAM, but I'd advise to avoid that mentality and just get the 60ns VRAM so you can remove that bottleneck and potentially have more fun. For me, it's not about 40MHz or 45MHz being "fast enough" but rather a matter of "how fast can this machine go!" Now, there's a difference between the fastest clockable speed and one that is stable for hours on end, but for the most part, I can reach 47MHz just fine and still boot into any compatible OS. I can even go to 49MHz and boot just fine into System 7.1 (ignoring 7.61 and OS 8.1). And for short periods, I can even use 50MHz. None of that fun would be possible with VRAM slower than 60ns.

Now, I have heard at least one person tell me (I think it was @phipli) who said they could reach 50MHz speeds without the need to use OS CON capacitors in their recap. But if memory serves me correctly, he has a 475, not a 575 like I do. When Kay Koba had solid tantalum caps on his 575, he wasn't able to reach 50MHz speeds. I then came along and decided to use lower ESR OS CON caps on my 575 motherboard and I was able to reach 50MHz. I told Kay about that, then he replaced his solid tantalums with OS CON, and then he too (with the aid of fast VRAM) was able to reach 50MHz. So all this means is that if 60ns VRAM alone doesn't get you to higher clocks, you need to consider the capacitors on the motherboard.

Of course, not every 040 is able to overclock to 50MHz, especially the ones made for 25MHz operation. But in my testing I found that the LC edition 040's, without any FPU, tend to overclock lower than the 040's with an FPU. Maybe that's a fluke in my testing, but I can't test anything outside what I own. I'm just reporting it. And the higher the clock rating of the 040 processor, the more likely you will be to hit 50MHz in your overclocks.

Then you need to heatsink and possibly fan to ensure you can maintain your overclocks.

Hope this helps!

Thanks for all that info! I wonder if my first order of business here should be to get a heatsink, because I've noticed that I can only achieve a stable overclock to 45MHz while the CPU is not too hot. Once it gets hotter, the computer freezes at 45, and I can only stably do 40MHz.

 

[JDW]

I wonder if my first order of business here should be to get a heatsink...

ANSWER: Yes!

My thread about Heatsinking the 040 is here:

https://tinkerdifferent.com/threads/68040-cpu-heatsink-clip-for-color-classic-mystic-lc575-motherboard.4349/

And to supplement that thread, please note that I made two videos about heatsinking an 040 on the LC575 below, and those were made before I used the "Heatsink Clip" discussed in the thread I linked above. Any of these solutions will work though.

NOTE: If you go with the massive copper heatsink shown in the lower video above, you won't need to worry about a fan. There's already airflow due the the main Color Classic fan and that combined with that massive cooling solution should be more than adequate. But if you want something more compact, then adding a 40mm Noctual cooling fan is helpful.

Can you get away without a fan and just use the 45x45mm heatsink mentioned in my earlier video, which wouldn't need the heatsink clip and just use thermal tape? Yes, if your overclock isn't maxed out. The higher your clock speed, the hotter it will get, especially if you have one of the very old 1990's revision 040 chips. Some over those get very hot even with modest overclocks to only 40MHz. So it largely depends on your chip revision and clock speed.

 

[phipli]

I honestly never thought that NOT having the VGA mod on a Mystic would create trouble for 475 Overclock. It would be good to have at least one other person confirm that same problem, so then @phipli could possibly update his 475 OC Blog page about that. But no, there shouldn’t be any harm to using Wish I Were all the time.

I... if your machine doesn't think that it is a supported machine because you hacked your OS, there isn't much I can do.

The software crashes if you try to run it on a real LC 580 so it wont run on something that is reporting as a 580.

 

[Marconelly]

Can you get away without a fan and just use the 45x45mm heatsink mentioned in my earlier video, which wouldn't need the heatsink clip and just use thermal tape? Yes, if your overclock isn't maxed out. The higher your clock speed, the hotter it will get, especially if you have one of the very old 1990's revision 040 chips. Some over those get very hot even with modest overclocks to only 40MHz. So it largely depends on your chip revision and clock speed.

Would it be possible to use a thermal tape with the large copper heatsink? I'm not so much interested in maximum performance, but would rather keep the machine as silent as possible (I've already installed a Noctua fan as per your other video's instructions!) I'd also try to install it in as simple way as possible., so I wouldn't want to pull the CPU out and use clamps, etc.

 

[JDW]

Would it be possible to use a thermal tape with the large copper heatsink?

Yes. But as shown in my Big Copper Heatsink video, if the heatsink bottom and 040 top aren’t perfectly flat, it is possible that the tape made not make uniform contact across the entire top of the CPU. Which means heat would only be transferred to the heatsink at points of tape contact.

The huge advantage of using paste and adhesive like I showed in my video is you don’t have to worry about any curvature. Paste fills the small gaps. And of course you get the benefits of slightly better thermal transfer too, compared to tape.