Overclocking the DC and where to get the Increase

[Morph]

That's fine, ain't no harm to it.

I may go back to it again another day, but I'm within firing distance of accomplishing a couple big things for the DC community as it is. All things must be prioritized.

[ßüboni¢ $oñic]

uh what does this thing do to ur DC?

[Morph]

*Suggests reading the whole topic and Googling*

[ptr.exe]

Hey Morph, sorry to hear about the bad luck.

I too worked on this for a while but soon gave up out of frustration.

I've still got a stack of spare DCs and hopefully I'll try this again sometime, I'll hit 300Mhz one day

[Morph]

I read your PM, but my interwebs suck as of now, and am unsure about even the reliability of this post.

The custom GD cable. I took 2 old ATA33 IDE cables, and diced them up so I had 2 cables for even pinage for every interconnect on the mainboard and Rom GD connectors. I basically graverobbed from an old non-working DC, and took the male and female connectors from it's mainboard and GD-Rom respectively.

I tried all the soldering myself, but gave up out of a combination of frustration and a short attention span. I then sent it to a guy I know from another website. Amazing with a soldering iron, etc, I got him to work with it.

The result was a functional (but fragile, as I learned later) GD-Rom cable. Wasn't more than 7 inches long. He used some plastic stuff to kind of mold the ends so the wires remain out of contact with one another.

Worked fine, its a shame I snapped it. I was not about to pay to get it fixed, so, scratch that.

On the other hand, I am experimenting with another method. I am going for no records with this one, but it involves removing the spreader plate from the main metal board on early Rev1 DC's (to compensate for the loss of the Heatpipe Cooler), and replacing it with a couple of ULTRA low profile i486 heatsinks someone had tossed out with the proc's and all.

I'll pull off the bit of metal covering the back vent, and place a fan to blow air in. Perhaps that will work.

[ptr.exe]

Thanks for the info, my intention with the GD cable was to make space for some nice big heatsinks, probably some stock Socket A HSFs I've got lying around.

But I think improved cooling wont help much without the vcore increase.

[quzar]

you may be able to get more speed out of a rev2 dc. all rev2s (that I know of) have an sh 200R model processor (as opposed to 200) which according to rensas was a non-functional update, which usually means decreased energy use and decreased heat output.

[Morph]

you may be able to get more speed out of a rev2 dc. all rev2s (that I know of) have an sh 200R model processor (as opposed to 200) which according to rensas was a non-functional update, which usually means decreased energy use and decreased heat output.

Of course, that is still assuming that:

A) It is voltage related.
B) The Rev2 is undervolting when overclock is tried.
C) The voltage can be changed somehow.


I might be able to get my mits on a digital camera at some point or another, in which case I will take pictures at my progress. Again, not going to 300 (haven't bothered with voltage), but I am running @ 270Mhz rather nicely.

Also, my Rev1 DC sports an "R" CPU. And, as a side note, I am not necessarily certain that the CPU is the bottleneck. We have to take into consideration typical RAM speeds and limitations. If anything, the RAM is probably bottlenecking.

A Rev1 board I have (just laying out), sports 8ns (125Mhz) Low Density memory for the GPU and the Sound systems. Heres where the fun part comes in, the main system RAM is rated for 10ns (100Mhz). So, if any RAM is going to put a strain, it's going to be the system RAM (seeing it'd be a full 50% over-spec).

For reference, the RAM that is on the left side of the GPU/Northbridge and above the PSU connector is the GPU memory (4x 2MB chips), and the RAM that is on the right side of the GPU/Northbridge and next to the Ext Connector are the chips for the Sound system (1x 2MB chip). The system memory would one of the chips below the SH4, and one on the right side, both right next to it (2x 8MB chips).

Sega basically saved money, by getting larger, slower chips for system memory, and smaller faster chips for GPU and sound memory. So, if we are looking for a highly overclockable Dreamcast, suggest that people look for a Dreamcast with system memory above 10ns.


Using a GPU RAM chip for example:



Thats how you identify ns speed. To find total speed, take 1000, the divide it by the ns # (for example, 8), and you will get the maximum rated speed.

Get huntin!

[kohan69]

Good post Morph, I will now which of my 6 dreamcasts I can expect the best clocks from

Question- did anyone dare to change the clockspeed down or up WHILE A GAME WAS RUNNING ?!

[Morph]

Yes, ptr mentioned that he did, and he can no longer run at 200Mhz. "Hotswitching" is not reccomended, because you are halting and restarting the entire system when you do. The 33Mhz signal is multiplied by 3 to run the entire unit, not just CPU, GPU, and memory.

And remember kids, small "ns" numbers yield higher clockspeeds. Simple equation for SDRAM:

1000 / ns-speed = max rated speed

Example: 1000 / 8ns = 125Mhz

I can't remember where the whole 1000 thing came from, I assume it was from me cutting corners.