Overclock your megadrive!

mtxblau

Mid Boss
Wow, that's pretty neat. But what games are there that the lag gets that bad? Off the top of my head I can't really think of any. Maybe in X-Men2... any others?
 

it290

Established Member
Thunderforce 4/Lightning Force.. although it's almost needed in some parts. And several other shooters as well (grindstomer for example). Also, it would be cool to play sonic and not have slowdown when you lose all your rings... or Sonic CD without all the excessive slowdown period.
 

racketboy

Established Member
Gunstar Heroes lags at times when there is a lot of blowing up going on

I should try overclocking some, painting them blue and selling them on eBay as a RARE Limted Collectors Edition Super Sonic Speed Genesis with an extra dose of Blast Processing
 
I'm really curious about this mod. I've got Panorama Cotton on a tototek cart, and it's one game that could really benefit from this. Although the slowdown rarely get's very bad at all, the game actually dips down very often...like half the time you play. In hard mode, it's damn near constant.

I'm kind of a newbie at this stuff, but I'd still really like to give this a shot. I've got a genny 2 I never use anyway. First, though, I'd like to hear from someone else who made this to work, and I'm also curious about how the Sega CD and 32X respond to it. Some more detailed instructions would be cool too, let's hope that guy posts pictures.
 
If it's so easy to get the CPU on the Genesis working faster, then why didn't the original design engineers build it to have a faster clock speed in the first place??

For that matter, if that CPU is capable of producing 2X to 3X its normal output, why was the chip only rated for the slow speed? I'm not sure I understand this fully...
 

Des-ROW

Established Member
Originally posted by it290@Mar 11, 2004 @ 12:19 PM

Yeah, come to think of it, it would probably break a lot of 32x/Sega CD games.

The processors would not be able to synchronize correctly.
 

it290

Established Member
If it's so easy to get the CPU on the Genesis working faster, then why didn't the original design engineers build it to have a faster clock speed in the first place??

Well, it's like overclocking anything else. It decreases the life expectancy of the chip, and not all 68000's are able to do it as well as others. Motorola rated the chip at 7mhz, so that's what Sega went with. Kind of like when you buy a Dell, it's not overclocked when you get it. ;)

The processors would not be able to synchronize correctly.

Yup, pretty much. Although it would probably work w/some games. And there would probably be a way to do this mod and still retain more compatibility (while still reaping the benefits). The guy did mention a switch method however, which is a good work-around.
 
Interesting comment from the slashdot page:

"As I recall, by the end of life the Motorola 68000s were all made as 16MHz parts. The slower parts were simply not made or sold any more. Also, even when they were genuine 8MHz parts, they were pretty reliable with 50% overclocking; we did this sort of thing all the time in Atari STs before the 68020 and 68030 upgrades got popular.

There were limits to what you could gain though, since the 68000 had no on-chip caches of any kind and the system bus generally couldn't handle as much of a speedup. The better upgrades included a memory cache with the accelerated 68000 on a daughterboard that plugged into the original CPU socket, to allow the processor to run at full speed without disturbing the rest of the system..."

Could be the reason why this guy got his up to 16MHz so easily. He said even with all that, the chip only rose a few degrees in temperature, so this would make a lot of sense. Although if it is true, I bet you couldn't overclock a model I MD. Hopefully this would work on most model IIs.

EDIT: Better comment
 

it290

Established Member
Hmm, interesting. Yeah, that daughterboard type upgrade was exactly what I was thinking for retaining 32x/SCD compatibility.
 
From what I remember a 68010 has a 10K cache so that may help and it is pin compatible with the 68000 so that may be a better option.Its also 14Mhz I think cant remember the speed.

Commodore used them to replace faulty 68000`s in A500`s when supplys were tight.Only in repaired models some time in the late 80`s.

Its a rare chip though
 
No the A600 was a disgrace a hacked up cross between the 500+ and 1200 it was basically a 500+ with PCMICIA port and IDE port for a 2.5" hardrive and that was it the CPU,RAM etc was all A500 (68KCpu and 1Mb RAM)Most came with 2MB and a small hardrive.Oh and some fool removed the NUMERIC Keypad!But there was some accelerators for the A600,they were as rare as hell for 500 series.

The A1200 had the 68EC020 a 020 CPU with 24 bit addressing or somet if I remember,and about 3 times as fast as 68000 I think.

Its not a full 68020 budget reasons,and hence some problems exist because of this.
 
Originally posted by Des-ROW+Mar 12, 2004 @ 07:57 AM--><div class='quotetop'>QUOTE(Des-ROW @ Mar 12, 2004 @ 07:57 AM)</div><div class='quotemain'>
Originally posted by it290+Mar 11, 2004 @ 12:19 PM--><div class='quotetop'>QUOTE(it290 @ Mar 11, 2004 @ 12:19 PM)</div><div class='quotemain'> Yeah, come to think of it, it would probably break a lot of 32x/Sega CD games. [/b]


The processors would not be able to synchronize correctly. [/b]


This is largely dependent on the game. The ones that did proper handshaking would work on an overclocked system; but there are a good number that depend on certain things occuring in order.

In addition there are probably Genesis games that timed things using loops. Such games would likely break on an overclocked Genesis.

<!--QuoteBegin-it920
@

Hmm, interesting. Yeah, that daughterboard type upgrade was exactly what I was thinking for retaining 32x/SCD compatibility. [/quote]

Wouldn't work. The problem isn't that the SCD and 32X hardware can't handle the Gen 68K having a faster FSB, its that some of the software is dependent on the amount of time it takes to run on the processor. Obviously the amount of time taken will decrease as the processor speeds up.

<!--QuoteBegin-Dr_Frankenmiga


From what I remember a 68010 has a 10K cache[/quote]

The 68020 had a 256 byte cache. I'm not sure about the 010 (it's not on Motorola's site anymore), but it certainly didn't have a 10K cache.
 

Alexvrb

Established Member
Originally posted by Mask of Destiny+Mar 13, 2004 @ 02:31 AM--><div class='quotetop'>QUOTE(Mask of Destiny @ Mar 13, 2004 @ 02:31 AM)</div><div class='quotemain'>
Originally posted by Des-ROW@Mar 12, 2004 @ 07:57 AM

<!--QuoteBegin-it290
@Mar 11, 2004 @ 12:19 PM

Yeah, come to think of it, it would probably break a lot of 32x/Sega CD games.


The processors would not be able to synchronize correctly.

This is largely dependent on the game. The ones that did proper handshaking would work on an overclocked system; but there are a good number that depend on certain things occuring in order. [/b][/quote]

This is kinda what I expected. But, I guess that is one good reason to install a switch if you were to do something like this. Could you overclock the SCD as well, and keep the ratio the same? How does the SCD 68k get its clock anyway?
 
Originally posted by Alexvrb+Mar 14, 2004 @ 01:14 AM--><div class='quotetop'>QUOTE(Alexvrb @ Mar 14, 2004 @ 01:14 AM)</div><div class='quotemain'>
Originally posted by Mask of Destiny@Mar 13, 2004 @ 02:31 AM

Originally posted by Des-ROW@Mar 12, 2004 @ 07:57 AM

<!--QuoteBegin-it290
@Mar 11, 2004 @ 12:19 PM

Yeah, come to think of it, it would probably break a lot of 32x/Sega CD games.


The processors would not be able to synchronize correctly.


This is largely dependent on the game. The ones that did proper handshaking would work on an overclocked system; but there are a good number that depend on certain things occuring in order.

This is kinda what I expected. But, I guess that is one good reason to install a switch if you were to do something like this. Could you overclock the SCD as well, and keep the ratio the same? How does the SCD 68k get its clock anyway? [/b][/quote]

The Sega CD has its own crystal oscillator (around 50MHz or so IIRC). This is divided down into a 12.5MHz clock (probably by the graphics co-processor) and is fed into both the 68K and the PCM chip (possible others as well). Overclocking the 68K would cause samples to play back too fast (the sample frequency of the PCM chip is relative to the clock). If you hacked the PCB up a bit, I suppose you could isolate the two clock signals, but it would require a good deal of effort with little reward.
 
I successfully OCed my Gen 2 to 10MHz using an oscillator. Too bad I couldn't get it to 12 but it just kept locking up. There is a difference in some games but when trying to use my 32X, some things go out of sync or have weird sound problems. I'm hoping to overclock my x'eye next (i've got 2) and see if i can make Samuri Slowdown (Showdown) run at a normal speed. I'm thinking if I run the Gen proc off the clock from the Sega CD half (12 MHz instead of 7.3) they won't go out of sync since they're on the same clock. Tell me if you have any questions about OCing your Genesis, I might be able to help.
 
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