gregg@unix386.Convergent.COM (Gregg Donley) (12/02/89)
I have some questions for True Mac Hardware Hackers Only. These all relate the original 128K, and 512K machines. What is the total RAM limit on these logic boards? I know that Dove makes a 1.5 Meg expansion board that brings the total up to 2 Megs, but I also believe I heard someone on the net say that they had one that went up to 4 Megs. Whatever the limit is, what is the limiting factor? Secondly, what are the allowable memory increments and what determines them. For example, there are 128K, 512K, 1M, 2M, 2.5M(?), 4M(?) upgraded machines but I haven't seen 256K, 1.5M, etc. How does the system determine what the size is? Does it get polled by ROM code during boot up? If so then are there any incremental limits? Is the OS flexible enough to adjust stacks and heaps and such to take advantage of any size? Do anythings like the screen and sound buffers move? Finally, has anyone experimented with their own home-built upgrades? If so I would be interested in hearing about your interface between the expansion ram and the existing system. Obviously, I am in the process of designing my own upgrade and am looking for advice (there is only so much you can deduce with an ohm meter and a logic board!). If anyone has any insight into any of these questions or is interested in whatever the final outcome of my experiment is, drop me a line. Oh, one more thing, I have one of those Mac Snap expansions that was originally only partially populated yielding a total of 1M. I added the additional chips only to find there are a couple of resistors that need to be added that I don't know the values of. If there is anyone who has one of these and doesn't mind opening their machine to peek at it, please get in touch with me so I can ask you about these components. Thanks! +----------------------------------------------------------------------------+ | . . . Any resemblance between the above views and those of my employer, | | my terminal, or the view out my window is purely coincidental. | +------------------- gregg@unix386.Convergent.com ---------------------------+