russ@convex.com (Russell Donnan) (05/03/90)
{In article <12460@wpi.wpi.edu> jhp@wpi.wpi.edu (John Petrangleo) writes: {>In article <7965@goofy.Apple.COM> dwb@sticks.apple.com (David Berry) writes: {> {>> Paged virtual memory to be precise (as opposed to segmented...) Under {>> A/UX 2.0 you are allowed to create a mac with up to 16Meg of memory. {> {>But I though that the MacOS would only allow 8 megs no matter how much memory {>you physically had installed. { When the MacOS is run in 24-bit mode (currently the default) the ROM { starts at 8 Meg and the slots at 9 Meg. Thus, you are limited to 8 { Meg of memory. Since A/UX runs the MacOS in 32-bit mode, the lowest { non-ram address is the ROM at 0x40800000. At least in theory we could { create a mac with as much as 4 gazillion bytes of memory. Currently { we have a limit of 16 meg. { David W. Berry A/UX Toolbox Engineer { dwb@apple.com I have to disagree with you, in theory at least. Since the majority of us Mac users still use: 128k, 512k, 512ke, Mac Plus, Mac SE, Mac II, and Mac IIx; without some funny finageling, we are always going to be limited to 8Mb because of the change in HW required to use 4Mb SIMMs. Now, you may argue that you can plug 4 1Mb SIMMs into a single SIMM socket, and you can. BUT, this is not a simple nor readily available solution. I'm also not certain whether or not an SE power supply would appreciate 128 RAM chips (16Mb x 8 1Mbx1) dragging on it. (~20W?) If this theoretical system had an internal HD, and a video card... It would be a burden even on a II series, no doubt, depending on the size of internal HD, and how many NuBus cards you had. Looks like the memory upgrade path for the II, IIx -> IIfx; and SE -> SE/30. Cheers! -Russ -- Russ Donnan, (214) 497-4778, russ@convex.com Convex Computer Corporation, 3000 Waterview Parkway, Richardson, TX -"To capture the essence of an opinion takes but one lawyer."