Using an HD20 with a 128k Mac

[CC_333]

Perhaps the RAM sizes are set wrong in Get Info... (or is that not a thing on the 128k?)

c

 

[yuhong]

Perhaps the RAM sizes are set wrong in Get Info... (or is that not a thing on the 128k?)

c

Not a thing unless you are running Switcher/MultiFinder

 

[CC_333]

Which isn't really a thing on a 128, I guess.

Hmm, I don't know, then. I suppose this is why so many people were eager to upgrade their RAM.

If one upgrades a 128 with Plus ROMs, do the extra HFS/HD20 routines still use extra RAM?

c

 

[uniserver]

this i am not even sure of... i think G said it does use up 2k of ram.

 

[Mac128]

Oh well, I will try to get a replacement internal 400k drive.

The machine seems to work ok with an external 800k drive (in that it will read 400k disks and boot off it).  From what i have read, though, it cannot write to disks.

This may help ...

Formatting 800K MFS Disks With 64K ROMs

There are numerous threads discussing this as well, but doing a search doesn't seem to pull them up for some reason. 

 

[Dog Cow]

Which external 800k drive do you have? Is it the one that also works with the IIgs (It has an eject button that doesn't do anything when connected to a Mac) or the slimmer Mac specific one? The latter won't boot a 128k or 512k with the original ROMs. Assuming it is the IIgs one, on the other hand, that one is a "universal replacement" and will behave like a 400k external unless...

The A9M0106, commonly used with the IIgs, will boot an 800K MFS disk on a Mac 512K.

Note that if you WERE to upgrade your Mac to 512k to work with the HD20 you'd still be limited to system... 4.2? unless you do the ROM swap to make it a 512Ke, in which case it will run System 6, very poorly.

Apple kept supplying 64K ROM patches through System file version 4.1. But you can copy the patches into newer system files to regain support for the 512K. A stock Mac 512K can in fact run System 6, but you need the right patches in it.

If one upgrades a 128 with Plus ROMs, do the extra HFS/HD20 routines still use extra RAM?

They still use the low-memory globals and have their system heap data structures for Drive queue, etc. But because HFS and the improved Sony disk driver are in the 128K ROM, they won't be loaded into RAM on any system that has this ROM. That check is done at boot time in the System file.

If the 128k has 128k of RAM, it will not work with the HD20.

Not strictly true. There's a check in the System file that can be NOP'd. One other change is needed too, and then it will load on a Mac 128K with 64K ROM. But it won't be very useful, because it'll take up about 32K of RAM, leaving you with something like 60K or so for running an application.

Even with Plus ROMs installed (which effectively creates a "512Ke" with only 128k of RAM) I don't think you can use an HD20 on a 128k Mac. Maybe someone here has tried it and can prove me wrong but I don't think there's enough RAM to effectively run any software once the overhead of the HD is added. (As I recall the one reason to make a 128ke was to add limited 800k floppy support.)

You can use a Hard Disk 20 on a Mac 128Ke, that is, a Mac with 128K of RAM and the 128K ROM. I did it, and have a screenshot from a Mac 128Ke with an HD20 mounted, towards the end of my Hard Disk 20 article. This configuration fully supports the Hard Disk 20, HFS, and double-sided disks.

 

[Gorgonops]

You can use a Hard Disk 20 on a Mac 128Ke, that is, a Mac with 128K of RAM and the 128K ROM. I did it, and have a screenshot...

This is some heavy-duty thread necromancy here. And just for the record, this was already addressed. (IE, it apparently does work, but you can't run a number of pieces of software like MacPaint that need a *whole* Mac 128k because there *is* still additional RAM consumed compared to a floppy-only system, so saying "it works" is a statement that really needs an asterisk.)

Apple kept supplying 64K ROM patches through System file version 4.1. But you can copy the patches into newer system files to regain support for the 512K. A stock Mac 512K can in fact run System 6, but you need the right patches in it.

Out of curiosity, is how to patch later systems to run on the 64k ROM documented anywhere? That might be a legitimate reason to reopen the topic.