Macintosh LC 475 ..... need a little help

[Zensor]

I have a Macintosh LC 475 here - does anyone know what kind of circuit board it is that goes over the fan?
I couldn't find any pictures/information about it on the internet.

THX - Stephan

(and if anyone knows..... how can i remove the circuit board without destroying anything)

 

[Fizzbinn]

No, but I’m intrigued! It looks like a CPU upgrade of some sort, plugging into the logic board CPU socket? Perhaps a Quaddoubler? or L2 Cache? Does the machine boot at present, if so can you run Tattletech or some other utility that reports CPU speed, etc?

If is is just connected to the CPU socket you could probably remove it by gently lifting up from both sides of the board (pulling up in the middle over the socket), perhaps slightly rocking it back and forth while pulling to get started.

 

[Zensor]

here is a side view (i don't dare to pull it with more force)

btw....i'm trying to get the mac up and running these days

 

[Kai Robinson]

That looks very much like a speed doubler - or L2 cache, as @Fizzbinn mentioned. You can get it out of the socket by gently wiggling it and pulling on it, or you can lever it with a plastic spudger?

 

[Zensor]

....nobody knows the part? (tried to pull it off but nothing moves - don't want to break anything)

 

[Kai Robinson]

....nobody knows the part? (tried to pull it off but nothing moves - don't want to break anything)

You likely won't break anything - just needs to be unplugged from the socket it's in - sometimes you just need to take your time levering it back and forth with a plastic tool, or your fingers.

Hard to tell what it is for definite, as the parts are mostly on the side you can't see - we're only able to make an educated guess based on what it's plugged into (the CPU socket).

 

[Zensor]

...the back part of the circuit board just floats above the fan - the front part seems fixed on the cpu

 

[Zensor]

You likely won't break anything - just needs to be unplugged from the socket it's in - sometimes you just need to take your time levering it back and forth with a plastic tool, or your fingers.

Hard to tell what it is for definite, as the parts are mostly on the side you can't see - we're only able to make an educated guess based on what it's plugged into (the CPU socket).

...in which Macintosh LC is a CPU installed that you can pull out of the socket ???

 

[Zensor]

That looks very much like a speed doubler - or L2 cache, as @Fizzbinn mentioned. You can get it out of the socket by gently wiggling it and pulling on it, or you can lever it with a plastic spudger?

I don't need a guide to destroying my mac I'm just looking for someone who knows this part

 

[MacKilRoy]

...in which Macintosh LC is a CPU installed that you can pull out of the socket ???

The LC 475 was the first LC to offer a socketed CPU.

 

[wottle]

I don't need a guide to destroying my mac I'm just looking for someone who knows this part

I think you got your answer. It's going to be nearly impossible to tell without removing the board. There are a lot of obscure 3rd party accelerators out there. You might get lucky and find someone who has the same board and would recognize the underside of the board without any markings, but you have a decent shot of identifying it if you remove the board, which is pretty easy and low risk.

 

[Zensor]

y'all were right (i was just too careful) with a little more force the circuit board came out

 

[MacKilRoy]

y'all were right (i was just too careful) with a little more force the circuit board came out

That is incredibly weird looking. Thanks for the photos !

 

[Fizzbinn]

So it’s a “Formac PL150-21”! …anybody know anything about it? . Not much I see in a quick Google.

It does look somewhat similar to Sonnet QuadDoubler, there‘s a nice low profile heat sink on the CPU, and a 89.9 clock crystal. Maybe it runs the CPU at half that, ~45Mhz? The CPU/heat sink being right over the fan to keep it cool?

 

[Branchus]

I'm pretty sure Formac was a European company that made display cards, so I'm wondering if this somehow expanded the display capabilities of the LC475? It's the "21" on the end of the product code that's making me think along those lines. Maybe it allowed display to a 21" monitor?

Just guessing.

 

[Kai Robinson]

y'all were right (i was just too careful) with a little more force the circuit board came out

From the images you've provided - it's confirmed my hypothesis - it's a clock doubler. The 89.92MHz oscillator is divided by 2 to give you 44.96MHz - the PAL's are there to decouple the onboard clock from the 68040 clock, letting the CPU run asynchronous to the bus, thus eliminating any issues with the serial or video.

You'll have a full fat 68040 chip under that heatsink, and not only that, it's designed to run at 45MHz, 20MHz over the stock speed of the system!

Formac PL150-21 is the name of the board, but no idea as to the name of the product as a whole. Formac Elektronik GmbH themselves closed the doors in the mid to late 2000's unfortunately, so there isn't even a parent company to ask about it - you really do have quite a rare piece of hardware there!

Luckily, it's simple enough that it's possible to reverse engineer

If you wanted to sell the card on it's own, i'd be down for buying it in case @Bolle can one day reverse engineer the PAL's on there!

 

[Bolle]

If you wanted to sell the card on it's own, i'd be down for buying it in case @Bolle can one day reverse engineer the PAL's on there!

Done already... The original is an 8 layer board, I imagine it's no fun at all routing the whole address and data busses through that narrow area on the board between host socket and CPU.

https://imgur.com/smyPV2Y

Got one of those too. You can swap the crystal for one with 100MHz and it will happily run the CPU at 50MHz.

 

[Kai Robinson]

Done already... The original is an 8 layer board, I imagine it's no fun at all routing the whole address and data busses through that narrow area on the board between host socket and CPU.

https://imgur.com/smyPV2Y

Got one of those too. You can swap the crystal for one with 100MHz and it will happily run the CPU at 50MHz.

...Why am i not surprised this has already been done?

 

[Zensor]

Thanks for the complete answers I couldn't find anything about it on google

 

[Zensor]

So it’s a “Formac PL150-21”! …anybody know anything about it? . Not much I see in a quick Google.

It does look somewhat similar to Sonnet QuadDoubler, there‘s a nice low profile heat sink on the CPU, and a 89.9 clock crystal. Maybe it runs the CPU at half that, ~45Mhz? The CPU/heat sink being right over the fan to keep it cool?

yes - the CPU floats above the fan