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Dual Processors - have to be same speed?

Old 04-14-02, 03:25 PM
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Dual Processors - have to be same speed?

When I upgrade my computer I plan on going with Athlon MP's and a dual processor motherboard. My question is...

Do I need to have chips of the same speed in there? Or can I combine an Athlon MP 1800 with an Athlon MP 1900?

Just curious.
Old 04-14-02, 03:37 PM
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same speed. and from what i understand sometimes they even have to be the same stepping. not sure about the last part though as i've never done the dual processor thing.
Old 04-14-02, 04:13 PM
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You could maybe get away with running both of them at the slower speed (or overclocking the slower one). But unless things have changed a lot since I last checked, the clock has to be the same for both of them.
Old 04-14-02, 07:27 PM
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Thanks for clearing that up...

It'll probably be a while before I upgrade, so hopefully by then 2 Athlon MP 2600's will be cheap.
Old 04-14-02, 08:25 PM
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As a practical matter, yeah, X and broadwayblue have it right.

But, if you want to impress chicks with the finer points of the EV6 "bus" technology that AMD uses for Athlons, then read on.

I put bus in quotes because EV6 isn't really a bus since it's a point to point interconnect. The northbridge runs a separate set of lines to each CPU so there's no contention for bandwidth on the FSB. That's why the 762 northbridge has over 900 pins.

Anyway, one of the cute things about that is that the CPUs in an EV6 system can theoretically be asymmetrical. Whether the OS handles it efficiently is another matter, but the hardware has no problem with it. However, it doesn't appear that AMD has chosen to explicitly support this feature. There have been some reports of people trying it, mixing Athlons of different speeds and even mixing Durons with Athlons. IIRC, it always resulted in stability problems.

In any event, all the mobo manufacturers state explicitly that they only support matching CPUs and only Athlon MP's at that. FWIW, I and a great many others, are using a pair of Athlon XP's which for all intents and purposes work just as well.
Old 04-14-02, 08:54 PM
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Originally posted by belboz
In any event, all the mobo manufacturers state explicitly that they only support matching CPUs and only Athlon MP's at that. FWIW, I and a great many others, are using a pair of Athlon XP's which for all intents and purposes work just as well.
I recall reading that you couldn't use XP without modifying the chip itself - something I'm not quite ready to do, but if you can use XP's, that might be a better way to go for me...could you expand on how you could use XPs and any motherboards they'd work for?
Old 04-15-02, 02:14 AM
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I bought my XP 1900's about 3 weeks ago which is about the time that the newer non-SMP XP's were just starting to get into the channel. Apparently, the only difference with the newer non-SMP XP's is that AMD has cut the L5 bridge on the surface of the packaging. That allows the newer mobos to differentiate between the XP's and the MP's and to not POST if it detects an XP.

Shorting the L5 bridge on one of the newer XP's allows it to function as before in a dual board. Apparently the process is even easier than the mod to unlock the XP's multiplier since you don't even need to carefully fill in the laser cut cavity with an insulating material. That was always the part that made unlocking an XP such a pain. To short the L5 bridge you can simply use a conductive ink pen and it's not much more difficult than unlocking the old Thunderbird Athlons with the pencil trick.
Old 04-15-02, 02:40 AM
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Originally posted by belboz
Shorting the L5 bridge on one of the newer XP's allows it to function as before in a dual board. Apparently the process is even easier than the mod to unlock the XP's multiplier since you don't even need to carefully fill in the laser cut cavity with an insulating material. That was always the part that made unlocking an XP such a pain. To short the L5 bridge you can simply use a conductive ink pen and it's not much more difficult than unlocking the old Thunderbird Athlons with the pencil trick.
That's what I thought - heard about the L5 bridge - again, probably something, that despite how easy it may be, is not something I'd want to risk trying.

Thanks for the info though.
Old 04-15-02, 03:54 AM
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Originally posted by Blake
That's what I thought - heard about the L5 bridge - again, probably something, that despite how easy it may be, is not something I'd want to risk trying.

Thanks for the info though.
Yeah, when I bought my XP's I fully expected that I might have to do the mod which didn't really bother me. But then I was one of those guys who was resoldering surface mount resistors on the old Slot A Athlons to overclock them. Now, that was a royal pain in the ass. Nowadays, I don't have enough time to do anything that requires that much work, but this mod seemed fairly trivial.

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