Upgrading ZIF G3 to G4 (MPC7410)

[jbenam]

Hi everyone,

Since I couldn’t find a 350+ MHz G4 for cheap for my Beige G3, I decided to make my own.

I own all kinds of soldering supplies and I have some BGA soldering experience.

Bought a 300MHz G3 (comes with 1MB L2 cache able to run at 2.8V) and 5x MPC7410 450Mhz.

From what I gather from here: https://datasheets.su/DS/NXP/MPCPCMEC.pdf

I should be able to lower voltage using the resistors to 1.8V (even so from what I can see on the ZIF module it should be set to 2.05V which is still supported by the MPC7410?).

As for the L2 cache, I should set the voltage to 2.5V, but I am not sure how.

The cache should come set to 3:2 “Late-write”, is that better than a pipelined 2:1 cache ratio?

So summing up:
1) Will anything blow up if I just swap the MPC750 for the MPC7410?
2) How do I change the L2 voltage? From what I can see the MPC7410 can’t operate L2 at 3.3V.

Hopefully these infos will be useful to other members as well. Tagging @dosdude1 since I know he has a lot of experience in these things.

If I can’t find any infos I was thinking of measuring Vcore on the BGA pins before soldering the new CPU in while messing with the resistors. Worth a shot.

Thank you for looking!

 

[dosdude1]

Unfortunately, so far I have been unable to find a way to change L2 cache voltage on those ZIF CPU boards, so I normally use a 7400 to upgrade those. Last I remember when I messed with this, the L2 cache is connected to the same 3.3V rail as other components/circuits on that board, so segmenting the L2 cache part of it off to even manually adjust voltage by way of adding a resistor divider or something wouldn’t be possible. I’ll have to go look at one again though to verify that.

Swapping a 7410 on as it is may kill the L2 cache portion of the 7410, though chances are it’ll be fine (L2 cache just won’t work). Though of course you need to ensure VCORE voltage is set appropriately before installing.

 

[jbenam]

Unfortunately, so far I have been unable to find a way to change L2 cache voltage on those ZIF CPU boards, so I normally use a 7400 to upgrade those. Last I remember when I messed with this, the L2 cache is connected to the same 3.3V rail as other components/circuits on that board, so segmenting the L2 cache part of it off to even manually adjust voltage by way of adding a resistor divider or something wouldn’t be possible. I’ll have to go look at one again though to verify that.

Swapping a 7410 on as it is may kill the L2 cache portion of the 7410, though chances are it’ll be fine (L2 cache just won’t work). Though of course you need to ensure VCORE voltage is set appropriately before installing.

Thank you very much for commenting on this issue.

I guess you mean that it will kill the L2 controller inside the 7410, right?

Sadly I guess it doesn’t make too much sense to do all this effort and not to have a functioning L2 cache as it would hamper performance massively.

Well, back to square one, I guess… obviously after I have purchased all this stuff, a Yikes G4 pops up for a decente price. Just my luck…

Anyway, an XPC7400 would instead be a straight swap with everything working, including L2, right?

Thank you very much for your help!

 

[dosdude1]

Thank you very much for commenting on this issue.

I guess you mean that it will kill the L2 controller inside the 7410, right?

Sadly I guess it doesn’t make too much sense to do all this effort and not to have a functioning L2 cache as it would hamper performance massively.

Well, back to square one, I guess… obviously after I have purchased all this stuff, a Yikes G4 pops up for a decente price. Just my luck…

Anyway, an XPC7400 would instead be a straight swap with everything working, including L2, right?

Thank you very much for your help!

Yes, XPC7400 will go right on, and work no issues with the 3.3V L2 cache. Just need to change the VCORE voltage and PLL config resistors for desired clock speed.

 

[LightBulbFun]

I can confirm that if you solder a 7410 to a G3 Beige ZIF card it will fry the L2 cache controller, not the whole chip that worked fine in another system, but just no more L2 cache.


the weird thing is there is a aftermarket G4 ZIF out there 550Mhz and 600Mhz, from IIRC PowerLogix, that does use a 7410 CPU, its one I have always been most curious about, because it for all purposes looks identical to a Yikes! G4 ZIF just with a 7410, so it begs the question how are they getting the 1.8V or 2.5V for the L2 cache? never had one myself to get up close and personal with sadly

I do wonder on these CPU cards where the L2 cache is tied to the 3.3V rail if its possible to physically cut some traces and then resupply the L2 cache with 2.5V or 1.8V from elsewhere?

 

[jbenam]

I can confirm that if you solder a 7410 to a G3 Beige ZIF card it will fry the L2 cache controller, not the whole chip that worked fine in another system, but just no more L2 cache.


the weird thing is there is a aftermarket G4 ZIF out there 550Mhz and 600Mhz, from IIRC PowerLogix, that does use a 7410 CPU, its one I have always been most curious about, because it for all purposes looks identical to a Yikes! G4 ZIF just with a 7410, so it begs the question how are they getting the 1.8V or 2.5V for the L2 cache? never had one myself to get up close and personal with sadly

I do wonder on these CPU cards where the L2 cache is tied to the 3.3V rail if its possible to physically cut some traces and then resupply the L2 cache with 2.5V or 1.8V from elsewhere?

It is indeed possible if you route some traces to another voltage source - the aftermarket G4 ZIF must be doing that. The 7410s has dedicated pins to L2OVdd.

Anyway I don’t think I will experiment with a 7410 anytime soon - as I have purchased a G4 Yikes for a very decent price. I will just get that G4 and slap it in my G3 Beige and call it a day.

I now have a bunch of 7410s at 450MHz I don’t know how to use

 

[lmartu]

I just did the same thing on my beige G3 and... while the CPU did work, the cache was disabled. I tried installing the sonnet drivers but nothing. Thing is... the G4 400 mhz with no cache is 50% slower in cpu Benchmarks than a G3 300 with cache... so not much of an upgrade if you can't get the cache going.
How did it work out for you?

 

[jbenam]

I just did the same thing on my beige G3 and... while the CPU did work, the cache was disabled. I tried installing the sonnet drivers but nothing. Thing is... the G4 400 mhz with no cache is 50% slower in cpu Benchmarks than a G3 300 with cache... so not much of an upgrade if you can't get the cache going.
How did it work out for you?

Did you try with a 7400 or a 7410? 7410s will get their cache controller fried when used on a G3 ZIF, as explained by LightBulbFan.

I just purchased a broken (and with missing parts) G4 Yikes for peanuts and put the G4 in my G3 Beige - overclocked it to 450MHz (IIRC) after placing a fan in the case and it works pretty well. Not sure I will ever bother with a 7400, at this point.

Still got that bunch of useless 7410s, though

 

[lmartu]

@jbenam everything is working now, after I used the daystar cache enabler

 

[jbenam]

@jbenam everything is working now, after I used the daystar cache enabler

Ah, so you did the same thing as I did and put a Yikes G4 in your G3 Beige - sorry didn’t read it correctly the first time.

I didn’t actually check if caches were enabled while I was playing with it some months ago, I will give it a look next time I power it on. Thanks for the tip!