Just checking to see if I understand this. On one Portable type (non-backlit) there's an ASIC which does house-keeping for RAM accesses.   When the RAM address space is accessed, …

I am. There was a video card I think . Hap has one

I am not aware of anything ever using the PDS slot on a portable. 

So a full upgrade plus empty PDS slot? Was there good PDS upgrade board or something useful?  If so, this RAM upgrade would be quite popular!

Really? Hap has a rom card. For one of his portables.

And this is the reason why. So they can decode the entire address space and use up all 9MB.  But I wont need to do that. all the address/data lines are broken out at the RAM conne…

Some portable ram upgrades are in the Pds slot and not the ram slot

I got the CPLD development breakout board on the way along with the JTAG. Once I get the RAM from trag, ill mount those up on a TSOP to DIP Adapter then I can make a simple wire-wr…

5 Meg total.  That explains the logic ICs near the 8 PRAM ICs on the backlit portable, that logic circuitry decodes the 1 Meg of onboard memory, plus it handles the DTACK and 0-wa…

is that 5 meg plus the one onboard or 5meg total? great progress .

ok, I answered my own questions. I found this note:  http://cdn.preterhuman.net/texts/computing/apple_hardware_devnotes/Portable%20(BackLit).pdf this basically explains the diffe…

The question is.. why cant you interchange? The bus is the same... The max ram also should not matter. The core chips are the same. Gttmfh only discussed one slot. And they dont …

I know my backlit ram did not work in my non backlit then was reminded that they were different so I did not interchange at all after that. Also the max ram on each is different. …

Can't imagine someone wanting a card that isn't maxed out. That would just be kinda nuts

I do want to make the card hold at least 8 Megs. But you dont have to populate all 8 megs. if you want just 1 meg, thats fine. put 1 chip on there, etc etc... 

Thats just it, I dont know. Which is why I am debating whether its worth the effort of designing a card or not.  I know I want 2 of them for myself. But the rest, is up to demand.…

trag said: That makes good sense. That's the dream. Run out of chips. Clean out a tiny portion of my attic. They are cool chips. A tiny piece of me squeals, "No, hang on to …

techknight said: The Toshiba has a weird little setup which is A-1, and its shared with I/O16. It appears I/O16 becomes A-1 in byte mode. But A-1 is not A1. And it doesnt rea…

techknight said: The portable and backlit portable both use 100ns ram. This is my first time making a ram expansion so if I have the logic wrong its a simple matter of moddi…

The Toshiba has a weird little setup which is A-1, and its shared with I/O16. It appears I/O16 becomes A-1 in byte mode. But A-1 is not A1. And it doesnt really explain what A-1 ac…

The portable and backlit portable both use 100ns ram. This is my first time making a ram expansion so if I have the logic wrong its a simple matter of modding the VHDL and flashin…

techknight said: I would rather have the Toshiba SRAMs trag. Why? Less CPLD lines I need the better. I will end up using an XC9572XL CPLD as the memory address chip select d…

oh man this is pretty exciting. 

I would rather have the Toshiba SRAMs trag. Why? because they are 16 bit and plus they have both an upper and lower byte access mode. This is a requirement for the 68000 as there i…

The portable keeps the card hot at all times however there is a standby signal. But I wouldnt use it. 3.3v logic isnt a problem. The question really wasnt about the design. More a…