You are not logged in.

#1 2015-11-17 20:12:08

bbraun
Member
Registered: 2014-05-29
Posts: 1,064
Website

PowerBook 5x0 CPU Card

While I was messing with the memory card for these machines, I also remembered this old page about replacing the CPU with a full 040 instead of the LC040.
The page says to use a MC68040FE33V, which is the 3.3V version of the QFP packaged 040.  Looking at my CPU card, the LC030 I've got is XC68LC040FE33B, which AFAICT is the 5V version.  It looks like the 3.3V version is 5V tolerant, so it can run with a 5V bus, but the power supplied to the CPU must be 3.3V.  At least that's my understanding.
So following those instructions and replacing XC68LC040FE33B with MC68040FE33V would be bad, it seems to me.

I have a difficult time finding 33MHz 5V QFP 040's, but it looks like 25MHz versions are plentiful.  I only have 33MHz cards though.
It looks like the difference between the 25MHz and 33MHz CPU cards is just the oscillator, which is an SG-615P operating at 12.5MHz on the 25MHz card, and 16.6667MHz on the 33MHz card.  Just replacing the oscillator should theoretically be enough to swap it from one to the other.  Or I could just try overclocking the 25MHz CPU to 33MHz and see how it goes...
Unfortunately, it seems like getting 12.5MHz SG-615's isn't that easy.  They're non-stocked most everywhere, and minimum order quantity of 250.

Offline

#2 2015-11-21 03:04:08

bbraun
Member
Registered: 2014-05-29
Posts: 1,064
Website

Re: PowerBook 5x0 CPU Card

I'm not actually sure the 68040 actually came in a 5V QFP package.  Here's the ordering information chart from the MC68040 User Manual:
040chart.png

In QFP package type, the full 68040 only has the V suffix.  In the PGA package, the 68040 came in both 5V and 3.3V variants (V and not-V suffixes).

So, according to my reading of the user manual, the full 040 isn't a direct swap for the LC040 on the powerbooks.  It might need a 5V -> 3.3V conversion.

BTW, the listings on ebay for the non-V suffix QFP 68040's are actually V suffixed.  So yeah, ebay.

Last edited by bbraun (2015-11-21 03:06:19)

Offline

Board footer

About ThinkClassic

ThinkClassic specialises in the maintenance, repair, restoration and modification of Vintage Apple and Macintosh computers. Ask questions and find answers about classic Apple desktops, laptops, accessories and peripherals.