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Thread: What's the different between the Signetics and Mortorolla CPU's?

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    Default What's the different between the Signetics and Mortorolla CPU's?

    Any differences? Why was the change made? I've read that all va2 and some va3 Genesis have the Signetics CPU. Just looking for some interesting info to read about this. Thanks

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    Road Rasher ironnick23's Avatar
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    One has a more stable overclock

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    Outrunner Eep386's Avatar
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    No appreciable difference in the stock configuration. Signetics chips themselves overclock just fine - on VA2 and VA3 Model 1 systems the bus logic, VDP or slow PSRAM gives out long before the CPU does.
    AFAIK, the Signetics chips used in Genesis/MD systems are all NMOS chips.

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    The only CMOS chips used in Mega Drive model 1s are the Hitachi ones, the Signetics and Motorola ones are NMOS. But yes, thereís no difference in functionality as Motorola licensed out the 68000 instruction set to other companies, so they are all compatible with each other and perform the same job. It all depends on who gave Sega the best deal on parts at the time. I have a Motorola MC68000L8 in mine, the side-brazed cerdip version, because it looks sexy. I also put a cerdip Z80 in mine, I just like the look and feel of ceramic packages.

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    Road Rasher ironnick23's Avatar
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    Quote Originally Posted by Eep386 View Post
    No appreciable difference in the stock configuration. Signetics chips themselves overclock just fine - on VA2 and VA3 Model 1 systems the bus logic, VDP or slow PSRAM gives out long before the CPU does.
    AFAIK, the Signetics chips used in Genesis/MD systems are all NMOS chips.
    Psram can be upgraded, no? Is the VDP different/better in later model 1 systems?

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    Quote Originally Posted by ironnick23 View Post
    Psram can be upgraded, no? Is the VDP different/better in later model 1 systems?
    PSRAM can be upgraded to proper SRAM, and I don't know whether one VDP is superior to another, I do however know that the "A" variant of the 315-5313 requires a 220 ohm resistor on pin 6 of the CPU, if that CPU is a Motorola, otherwise the console tends to crash.

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    Quote Originally Posted by Xaranar View Post
    PSRAM can be upgraded to proper SRAM, and I don't know whether one VDP is superior to another, I do however know that the "A" variant of the 315-5313 requires a 220 ohm resistor on pin 6 of the CPU, if that CPU is a Motorola, otherwise the console tends to crash.
    Is proper sram going to provide a more stable overclock to 10mhz? If I have swapped my cpu for a hitachi, would it be safe to remove this resistor from pin 6?

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    Quote Originally Posted by ironnick23 View Post
    Is proper sram going to provide a more stable overclock to 10mhz? If I have swapped my cpu for a hitachi, would it be safe to remove this resistor from pin 6?
    I donít know, and yes.

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    Outrunner Eep386's Avatar
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    I personally prefer the Signetics chips, because they're slightly thicker and heavier. But that's me, I like oddball stuff.

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    Iíve only seen a Signetics chip in the wild once, and that was in a VA6 PAL model, weirdly. I guess I like the Motorola chips best, as those are the OG 68Ks.

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    Quote Originally Posted by ironnick23 View Post
    Is proper sram going to provide a more stable overclock to 10mhz? If I have swapped my cpu for a hitachi, would it be safe to remove this resistor from pin 6?
    It has less to do with whether or not it is proper SRAM, and more to do with the timing margin available with the chip.
    'Real' SRAM chips usually can operate at much faster clockspeeds, especially the ones you pull from old 386-486 motherboards, so they're less likely to be a hindering factor when overclocking than, say, the very slow stock PSRAM chips.

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    WCPO Agent roadkill's Avatar
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    I don't mean to hijack a thread, but while you guys are on the topic of "Signetics and Motorola CPUs", is there any benefit to getting a Ceramic Gold Plated Motorola?

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    Quote Originally Posted by roadkill View Post
    I don't mean to hijack a thread, but while you guys are on the topic of "Signetics and Motorola CPUs", is there any benefit to getting a Ceramic Gold Plated Motorola?
    Longevity, better heat dissipation means longer life span. Although, I doubt any of the regulr plastic DIP CPUs will die in any of our lifetimes as it is. The only real advantage then, is that they look cool AF.

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    Road Rasher ironnick23's Avatar
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    I wish you never said that, all my capacitors are gold. Now I need gold heatsinks and this gold cpu

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    Quote Originally Posted by Xaranar View Post
    Longevity, better heat dissipation means longer life span. Although, I doubt any of the regulr plastic DIP CPUs will die in any of our lifetimes as it is. The only real advantage then, is that they look cool AF.
    Ah ok thanks, I thought maybe they might have ran a bit cooler or had slightly better performance, especially when overclocked. And yeah, they do look cool AF .

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