51MHz using your new 2-chip 60ns VRAM, or with the Mr.F. or Drake 60ns 4-chip VRAM?
"Spicy O'clock" project has started
- Thread starter Kay K.M.Mods
- Start date
I'm unqualified to speak, regarding caps and esr, a thought I had though, was the cpu, since we are overclocking and then there is the 'unknown' pedigree of many of them. It's just a hunch though. If we knew more, anything, about the grading process of the CPUs off the 'assembly line'...
Just for the record, ~49.5mhz seems to be my limit, above that I start to see apps quit with type 'x' errors. At least it seems to be, I'll be running today to further test stability.
CPUs take power in spikes. This is why capacitors are very important -- to satisfy the demands of power hungry chips quickly. When you overclock, the demands on the capacitors increase, but if the little resistor inside each capacitor (known as ESR) is too large, the capacitor cannot fully satisfy the needs of the CPU, and the result is a freeze or crash, which you may interpret as "I can't seem to overclock any higher." This is what Drake and Kay experienced on the LC575 motherboard until they swapped out their tantalum capacitors with OS-CON. We know that is true on the LC575 motherboard, but I don't have enough data from other people to know how it applies to other motherboards. In theory though, lower ESR capacitors should help. But in practice, well, I need the owners of those other computers to chime in during their overclocking experience to know for sure. Kay has a lot of experience, which is why I directed my previous post at him.
Individual RAM and VRAM chips can vary in performance, even if the design is supposed to be “low latency”.
I have observed variances in benchmark performance of my own VRAM when running a graphics benchmark, on the same machine in the same conditions.
When you sent two of my VRAM modules to Kay,
Additionally, the capacitors I used on my VRAM modules are different than the ones used on Drake’s, which could also contribute to some variances.
Also, I have found that different CPUs return slightly different benchmark results. Some higher than others.
Edit: strike through as I misinterpreted the email I received from Kay about this.
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Very true about VRAM chip variations.
By the way, the 68040 you kindly shipped to me was able to overclock to a max of 48.4MHz (rock solid stable frequency) in my Mystic when using your 60ns VRAM or Drake's. A second CPU that I purchased from UT Source (also with FPU, but with fake markings), was able to overclock to 49.2MHz using your VRAM. I also confirmed the same 49.2MHz max-stable clock speed with Drake's VRAM. So if someone buys your VRAM and finds they cannot overclock past, say, 48.5MHz or so, it very well could be a CPU limit (assuming they have OS-CON caps installed).
Hopefully, we'll get more CC Mystic owners to buy your VRAM and test with their OS-CON recapped boards so we can get more useful data. Should be interesting to see the overlocking limits reached when we have a couple dozen people all trying the same thing.
When overclocking on a modern Intel or AMD PC, there are numerous factors that make up the formula.
1. The quality of the individual CPU. Different CPUs individually allow different settings, and often require a specific voltage individual to that CPU in order to overclock. Heat also plays a role here.
2. Motherboard quality and ability. Some PC motherboards are better at overclocking than others, mostly due to design of how it is setup but also what components are used (including capacitors) and cooling of those components.
3. RAM quality. If memory is not fast enough or high enough in quality, it limits the upper limits of stability.
4. Power delivery. All of the above is dependent upon a quality reliable and stable power supply.
5. Temperature. Lower ambient room temperatures allow the components to reach higher temperature without affect. Cooling of components such as the CPU greatly affect the ability to overclock.
On a modern Intel or AMD PC, all of the above are part of a successful overclocking recipe, and having one part being deficient results in the entire system being unstable.
I could see the same applying to vintage hardware. One component in upper limit testing is what is the mask of the 68040 CPU being used, as it’s lithography could affect performance. Newer mask chips (legitimate ones), should theoretically overclock easier and higher than older mask chips.
I have tested a variety of 68040 chips and analysed their individual temperatures at 33mhz and found a variation of temperature from over 80’c to as low as 48’c. That alone would affect the limits of overclocking beyond everything else. If used on a board with OSCON caps, a 90’c CPU at 33mhz would not overclock very well.
To obtain the fastest possible 68040 clocks, one would need the most ideal design Mac logic board, with the best performing on-board RAM chips, a late-mask 68040 CPU, a good cooler and some thermal paste, good on-board capacitors, and very stable power delivery. Cooling of that system would also be crucial to ensure stability.
On the topic of the CPUs, Motorola binned them based upon order requirements. If Apple needed 25mhz CPUs, Motorola would simply test a batch at 25mhz, and if they passed internal testing, would be marked 25mhz. Those that didn’t, would be retested at 20mhz and masked off at that speed.
If Apple ordered 33mhz chips, the same process would happen. It’s very possible a 40mhz chip has a 33mhz or even 25mhz printing because that is the certified limit. However, I don’t think Motorola ever thought of these running higher than 40mhz so they never would have a process for certifying them above 40mhz.
So what does that mean? A 68040 CPU that is marked 33mhz may very well outperform one marked 40mhz. I would say it more depends upon the mask revision than anything. A “true” L88M 68040 at 33mhz should theoretically outperform an older 40mhz mask (take your pick on which one). I say “true” because over the past decade, but even more so over the past several years, recyclers overseas have pulled 68040 and 68LC040 CPUs off old machines, ground down the surface and reprinted them as 68040 L88M 40mhz. Which would make them “fake”.
My initial findings for 68040 CPUs that I purchased on eBay to test can be found here: https://tinkerdifferent.com/threads...fake-68040-cpus-especially-the-l88m-mask.820/
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Less chips means less variation. 2 chips is less than 4 which is exactly half. 50% less chance of variation between 2 chips which results in 50% better odds of positive results per stick.
Compared with the old design, The New SMC VRAM has faster access times & LED's.
When aircraft
fly they are required to have light indicators, our VRAM scores are so high we're also required to have the same indicators!
Interestingly, the CPU which would only clock to 48.4MHz measured about the same temperature as the CPU which overclocked higher, and both were around 60°C in my testing, with only a couple copper RAM heatsinks on them at the time (since I could not use my wired probe at the center of the CPU when the full sized 45mm heatsink was fitted. That didn't even include a blower fan on the CPU. Currently, I have a 45mm heatsink and a 40mm fan which screws onto that heatsink (thanks to Kay's screw trick) and blows down onto the heatsink.
If the recent 3D model that was produced by a member of this forum is ever released into the wild, it would seem to allow one to clip-down the gold color 45mm heatsink, which would allow use of Thermal Grizzly Kryonaut paste instead of thermal tape, thereby allowing (in theory) better heat transfer than thermal tape, and therefore even better cooling.
But overall, I believe there were issues other than cooling in my testing which had an impact on the upper overclocking limits of the two CPUs I tested, which of course would not be the same for everyone.
Regarding CPU thermal characteristics, my CPU appears to have reached a plateau of sorts. Increasing clock speed from just under 42mhz to ~49.5mhz has resulted in no, or minimal increase in the temperature as measured by a thermocouple placed between fins near the center of the heatsink. With an ambient room temperature of ~19C, the temperature reaches 41C after 'warmup', with the case top in place. If the case top is removed, it drops to 31C. There is virtually no space....probably only from the top of the fan body to the top of the screws, above the fan on the heatsink.
I may try my hand at devising some standoffs to give the fan some 'breathing room' and see if maybe 5mm extra space would help at all. Of course, this would disable the floppy...but I could still utilize my floppyemu.
This CPU was bought off Ebay and was advertised as an MC68040RC40A and L88M mask, also as a Coldfire CPU. I only researched 'Coldfire' after I ordered it and either it's not or I misunderstood what I read, as I didn't think it would be compatible! Which clearly it is.
I may try my hand at devising some standoffs to give the fan some 'breathing room' and see if maybe 5mm extra space would help at all. Of course, this would disable the floppy...but I could still utilize my floppyemu.
This CPU was bought off Ebay and was advertised as an MC68040RC40A and L88M mask, also as a Coldfire CPU. I only researched 'Coldfire' after I ordered it and either it's not or I misunderstood what I read, as I didn't think it would be compatible! Which clearly it is.
That matches my findings. My CPU temperature did not increase that much, even without a full heatsink or fan cooling, when overclocking between the said range. I found that quite interesting. You'd think it would and should increase, but it really didn't in any meaningful way. Even so, I followed everyone's advice and properly heatsinked and fan-cooled it. I think that will help as the temperatures get warmer. We into the Spring months already here in Japan. When summer hits, it will be harder to keep those overclocked CPUs cool enough by mere convection, so having a good heatsink and CPU fan is a very wise idea indeed, even though in one's testing it may not appear to have any impact on the maximum overclock ceiling.
After using my maxed out system for a short while, I have backed my overclock down to ~49mhz. Realistically, there probably isn't a big difference between 49 and 50 and stability improves the slower the clock speed! Just recently I installed System 7.6 to compare with 8.1. It has been more stable, at least on my system and there were small but significant (3% or more) improvements in graphics and disk scores. As far as stability is concerned, at ~49.5mhz, my biggest problem was errors/freezes when the Finder was in the background and the system was idle. Perhaps I should qualify this by saying 'after boot' stability. Booting is a problem at times ,more so when the system is warmed up, but interestingly this has improved after I disabled software termination on the SCSI2SD and added a terminating resistor externally.
Where are all of the 'other' Spicy O'Clock tinkerers????
Where are all of the 'other' Spicy O'Clock tinkerers????
I had issues with 7.6.1 and OS 8.1 above about 45MHz, but no issues at 49MHz with System 7.1. 7.1 is faster anyway, so I am happy to stick with that. With the Mr. Farenheit or Drake 4-chip 60ns VRAM, I could overclock to 49.5MHz, but after a while I would get the dust pixels trailing the arrow pointer, so I had to down-clock to about 49.2MHz. With the 2-chip red PCB prototype "low latency" 60ns VRAM that Kay Koba sent to me (currently in use in my machine), I can reach 50.1MHz and not get any pixel dust.After using my maxed out system for a short while, I have backed my overclock down to ~49mhz. Realistically, there probably isn't a big difference between 49 and 50 and stability improves the slower the clock speed! Just recently I installed System 7.6 to compare with 8.1. It has been more stable, at least on my system and there were small but significant (3% or more) improvements in graphics and disk scores. As far as stability is concerned, at ~49.5mhz, my biggest problem was errors/freezes when the Finder was in the background and the system was idle. Perhaps I should qualify this by saying 'after boot' stability. Booting is a problem at times ,more so when the system is warmed up, but interestingly this has improved after I disabled software termination on the SCSI2SD and added a terminating resistor externally.
Where are all of the 'other' Spicy O'Clock tinkerers????
Again, stability has not been an issue in System 7.1, so I would recommend all Spicy testers to start your overclocks in that OS and see what your maximum stable (and no pixel dust) clock frequencies are before you dive into 7.5.5, 7.6 and OS 8.1.
SMC-VRAM has been released!
Original post here:
en.infinityproducts.co.jp
Original post here:
SMC-VRAM 512KB 60Ns for 68040 Overclocking/ 2-PCS per set | infinityproducts
Satanic Mac Club 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!*The design base is from alxlab (Alexandre Marcoux). Sold with permission.https://github.com/alxlab-zone66x Specifications • 2pcs...
en.infinityproducts.co.jp
You prepared those faster than I thought. Wow.SMC-VRAM has been released!
Original post here:
View attachment 4826
SMC-VRAM 512KB 60Ns for 68040 Overclocking/ 2-PCS per set | infinityproducts
Satanic Mac Club 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!*The design base is from alxlab (Alexandre Marcoux). Sold with permission.https://github.com/alxlab-zone66x Specifications • 2pcs...
That basically means overclockers have the 60ns VRAM from Mr. Fahrenheit and now the SMC 60ns VRAM.
Now there are fewer excuses to make those old 68040 Macs faster with Spicy O'Clock!
But.....
has anyone discussed the ethics of wielding so much RAW SPEED??!?!1
has anyone discussed the ethics of wielding so much RAW SPEED??!?!1
So, Spicy O'clockers in the Northern Hemisphere, how are your machines handling warmer ambient temperatures? Before we finally broke free of near freezing temperatures in the early morning hours, the room where my machine lives, would see ambient temps below 20C. Currently, with daytime highs fluctuating between 24/32C and my house thermostat set to 25.5C during waking hours, the ambient temperature is ~24C in this half underground room. For the past month, I have been doing some programming, which has me using the machine for some hours a day. Ten or so days ago, my LC475, overclocked to 49mhz and running System 7.6, would start to go unstable after an hour or so of use. CPU temps would be getting close to 50C as would the inside of the power supply case. The power supply seems to be the culprit, as there is no fan to dissipate the heat. My solution has been to remove the top cover and run a small fan, blowing on the side of the power supply. This keeps the internal temperature down to the low to mid 30's. I can run for hours with no stability issues at all now. The CPU runs about 10C degrees cooler with the case off (fan installed on heatsink), but if I don't run a fan onto the power supply, it eventually warms up enough to start causing stability issues again.
I'm not the most adept tinkerer, but perhaps I could extend the power lead wires, to where I could move the power supply outside the case, as running without the cover on is less than ideal!
I'm not the most adept tinkerer, but perhaps I could extend the power lead wires, to where I could move the power supply outside the case, as running without the cover on is less than ideal!