PowerBook 500 Connector 'Destroyed Mold' - Just a Myth?

[frontein1]

Physical space is the difficulty with removable DIP chips, as there’s not much.

Maybe some kind of JTAG style connector onboard the redesigned CPU card with a special harness would be a possibility?

I wonder how reliable those JTAG connectors would be? However I know there is now a lot of room in the bay to the left where I replaced the spinner with a BlueSCSI. If JTAG could work, then this could be an area.

Another idea, and this might be a bad one, would be to 'poke' some holes in the heat sync that gets screwed in top of the CPU. That might give some room. Maybe tomorrow I'll pull one of my two 540c machines out and take a look at the inside.

 

[croissantking]

I wonder how reliable those JTAG connectors would be? However I know there is now a lot of room in the bay to the left where I replaced the spinner with a BlueSCSI. If JTAG could work, then this could be an area.

The ROM chips would still be onboard, I just meant the connector would be a way to program those chips (by exposing their programming pins to a harness) while the power is off.

Another idea, and this might be a bad one, would be to 'poke' some holes in the heat sync that gets screwed in top of the CPU. That might give some room. Maybe tomorrow I'll pull one of my two 540c machines out and take a look at the inside.

Seems like too much work and also a bit destructive, my aim with whatever I design is that it harmonise with the internal layout of the 500 Series if that makes sense.

The better way would be extend the CPU card design into the area usually reserved for the modem. You'd have space above if you didn't install a RAM card, and you would have quite a bit of space underneath as well (but still probably not enough for a DIP socket and chip).

Are you thinking to have removeable chips for programming just during development or is it a permanent feature you'd want?

Maybe we're thinking of two slightly different projects though - one is a dev board and the other is an end user product If you want to get into ROM programming now then we should look at a way to modify the stock CPU card.

 

[Trash80toHP_Mini]

Can't believe I missed this thread! Nice project!

Didn't see this mentioned, but not fully awake yet. If you're going for a Blackbird G3 card, PBX bus bridge ASIC for PPC 'Books is needed on the bottom of the CPU card would be the limiting factor, no?

Gotta dig up the thread, but there were some amazing later G3 variants. One specific version had so much on die cache that increasing memory might not be necessary? 3.3v leveling required, but 1400 cards have lots of board real estate available on the cache extension. Might be worth looking in to?

Then again, I was looking into doing a faster 1400 CPU with its higher memory ceiling. 1400 memory upgrades are more readily available than the Blackbirds.

Demolished plastics 1400s are probably the most available donors for desoldering PBX?


edit: as mentioned above, an SD replacement board in the HDD bay would provide available cubic for a load leveling board?