Using an HD20 with a 128k Mac

[khannonnd]

Hey there,

I currently have an HD20 with 6.0.8 installed.  If I wanted to get this to work with a 128k Mac (as a startup disk) I am assuming I have to move it down to System 4 or something.  Is it as simple as say, booting up the 128k Mac using a floppy, turning on the HD, erasing the HD's system folder, and moving the disk's system folder onto the hard drive?

 

[uniserver]

yup go down to a lower system... and make sure you have plus rom's installed, so it can natively boot the hd20, otherwise you will have to download the HD20 boot disk.  for the 128k 512k

 

[uniserver]

you could also buy a  rom kit from BMOW and boot from rom as well.   http://www.bigmessowires.com/mac-rom-inator/

 

[khannonnd]

yup go down to a lower system... and make sure you have plus rom's installed, so it can natively boot the hd20, otherwise you will have to download the HD20 boot disk.  for the 128k 512k

Ah gotcha.  So in order to *boot* from the HD20 on a 128k Mac I need to mess with the ROMs?  But I can use it as an external (non-bootable) drive if the HD INIT file referenced on this page is in the system folder of the boot disk: http://www.mac512.com/macwebpages/hd20.htm ?

I don't think I have the technical skills to mess with the ROMs on the machine, alas.

 

[tanaquil]

I am a moron when it comes to these things. khannonnd, are you talking about booting an actual 128K machine with a physical HD20 drive? Or some kind of virtual booting situation? I don't understand how you could have plus roms installed unless it's a virtual machine.

If a physical 128 machine, it sounds like you might need the HD20 floppy that others have referenced.

I am curious... I only have 512Ke/Plus machines myself.

 

[Gorgonops]

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.)

 

[khannonnd]

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.

 

[Gorgonops]

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 "HD20 init" (which also doesn't work on a 128k because it consumes too much RAM) or Plus ROMs are present, in which case it becomes an 800k drive...

But in either case if the drive works to boot the machine you'll be able to write to it fine. The stuff about not being able to write to 400k disks with a higher capacity drive applies to newer Macs.

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.

 

[unity]

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

 

[khannonnd]

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 "HD20 init" (which also doesn't work on a 128k because it consumes too much RAM) or Plus ROMs are present, in which case it becomes an 800k drive...

But in either case if the drive works to boot the machine you'll be able to write to it fine. The stuff about not being able to write to 400k disks with a higher capacity drive applies to newer Macs.

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.

So, oddly, I have both (M0106 and M0131) and they both will boot the machine.  I know for a fact the motherboard only has 128k of RAM based on the "About" thing under the apple menu).  I have attached a picture of the motherboard -- the ROMs haven't been upgraded have they?  I don't know what that would look like.

 

[Gorgonops]

Odd. I have heard that there were several versions of the 800k mechanism used in Macs, some of which have the fix to work around the divide-by-zero bug in the 64k ROMs, perhaps your M0131 is newer than mine.

 

[Gorgonops]

... and that said, checked the part numbers and your board does indeed have the original 64k ROM set.

I hate to suggest such blasphemy, but if the mechanism in your 800k external can boot the machine it might be possible to take it out of the case and install it internally.

 

[Canby Fat Mac]

Heres the Original HD20 Disk with system 3.2 

https://onedrive.live.com/redir?resid=F73182AF83ABB56%218075

 

[Canby Fat Mac]

Heres the Original HD20 Disk with system 3.2 

https://onedrive.live.com/redir?resid=F73182AF83ABB56%218075

Here an updated link, had to remove the last one.

http://earlymacintosh.org/disk_images/3.2%20HD%2020%20Startup.sit

 

[uniserver]

Why wouldn't a 128k work with a hd20 and plus rom's?   

It does, as i have tried this.  Both with BMOW's Floppy Emu and a real HD20.

and the rom's are just pop in, anyone could pop plus rom's in the MB.

yes 128k ram does limit what you can run anyways.

i was just talking to Steve about maybe selling a HD20 only pop on unit... no buttons, no switches, no screen

it could work with the 128k 512k plus, se, portable, IIsi, Iici, classic, classic II

and with some hackage could also work with the LC, LCII, Powerbook 100, SE/30, IIcx, Mac II

 

[Gorgonops]

Out of curiosity, what *can* a "128Ke" with an HD-20 attached run successfully? Folklore.org notes that some programs such as MacPaint left only a few hundred bytes of RAM free when run on a 128k, does that work for instance?

(Such a thing would be the reason it *wouldn't* work on a 128k that had to use the HD-20 Init driver with the original ROMs, as said driver consumes a bit less than 2k.)

If it comes down to the OP swapping bits on the motherboard personally I'd say they'd be better off upgrading to 512k instead of changing out the ROMs (or doing both). If I recall correctly from the conquest thread the chassis is from a 512k anyway...

 

[uniserver]

no i was not able to get mac paint to run.  but there are other apps that do work.   128 ram is quite limited.

 

[Gorgonops]

Considering MacPaint and MacWrite are pretty much the *definitive* programs to show off a 128k with I'd sort of rate not being able to run at least one of them a deal breaker.

 

[uniserver]

Well I don't know about MacWrite didn't try that . And to be honest even with the stock 128k roms and booting from a 400 K image with the floppy EMU I was still not able to get MacPaint to run so not really sure what was going on

But yes plus roms in a 128k gives you native hd20 booting