hkr4627@acf4.UUCP (02/15/85)
I too would love to see a 4MB mac but, correct me if I am wrong, I remeber reading that the heap/mem management code is configured for up to 512K. If this is indeed true you would have to retarget the dope vector for the mem management code to your own mem code which would be wise to the real mem size Hedley ihnp4!cmcl2!alaya!hedley
pc@unisoft.UUCP (Paul Campbell) (04/19/85)
<munch> Just an update on how my >512K mac is coming on. I have finally been able to get all the bits I need together in the same room ... and I finally started last weekend. I now have a 1Mb mac ... but its second set of memory is a little forgetfull at the moment, nothing some more decoupling wont fix. The mods are very simple, only the ram chips and 3 other commonly available chips (plus a few resistors and lots of capacitors). I put mine on a daughter board with lots of wires ... it doesn't look pretty, if you only want an extra 512K you could piggy-back the ram chips, this would make things much tidyer, but limit your future growth. At the moment my circuitry will expand easily to 2Mb, and once I figure out which pin on the VIA changes the memory mapping at boot time, it will go to 4Mb (probably I will need another chip :-( also I want to add some form of memory protection so that I can stop programs in a development environment from walking all over my ramdisks. I will be making a 2Mb board (once I figure out where to get the PC artwork tools ... Bishop Graphics or like ... any-one got any ideas in or near Berkeley/SF?). Once I have a stable system I will be publishing the circuit diagrams, building instructions in net.sources.mac, hopefully next week. More to come ... soon Paul Campbell ..!ucbvax!unisoft!paul "Let`s do the Mac ...." This is the obligatory disclaimer of Unisoft not being liable for anything, (except hopefully my paycheck at the end of the week :-)