View Full Version : Butchering iMac- IDE hotwiring?

10-22-2001, 06:31 PM
Is the revB iMac capable of a total of 4 IDE devices? (I see that the blue and white G3s are..).
I'd like to rip it to bits and graft in an IDE extension onto one IDE controller so I can use a Plextor 241040; that way I'm not tied to slow external USB CD writers,( I've got one of them already, an Iomega ).
I've disembowelled the beast already to upgrade RAM and also to fit a Samsung 60GB hard drive which works fine, so I'm not fazed by the technicality of it. The old drive now sits in an IDE/USB caddy as a back-up.
Obviously cable length has to be kept short and I'll need to rip a hole somewhere; probably the CD ROM slot as that might be on the way out....

10-23-2001, 01:57 AM
So, I think your out of luck on that. The B&W G3 has/had the Grackle memory controller and separate Ultra DMA33 hard drive controller and ATA3 ATAPI controller for the CD and ZIP. Four devices possible on 2 buses.

Your RevB has the new Uni-North Memory Controller and a single IDE port off the Key Largo I/O-Disk controller. The CD is Slave, the hard drive is master on the same connector. There is no second controller or bus to connect to.

Apple Developer for the imac is: http://developer.apple.com/techpubs/hardware/Developer_Notes/Macintosh_CPUs-G3/iMac_26Oct99/index.html

10-23-2001, 01:22 PM
iMacs actually have 2 IDE ports, but I do not think they support slave drives. One IDe port is standard 40 pin for the hard drive. But the CD-ROM IDE port is non-standard. Since the CD is a modified powerbook CD the IDE connector is compresses and thus the port for it on the mobo is too.

The only way you are going to get more devices onto you iMac is through USB, which is slow, or with a Sonnet Harmoni processor upgrade card, whihc adds firewire to rev A-D iMacs. But I don't think it is shipping yet.

- Chris

10-23-2001, 02:35 PM
The CD drive in early rev iMacs uses an adapter cable to connect the CD drive's Micro-ATAPI connector to the standard 40 pin port. I believe ricks is right also. The chipset that the iMacs used only supports two IDE devices and maps them.

10-23-2001, 03:22 PM
Well, I don't have one in front of me, I was reading the ADC where it said the CD-Rom was the slave. Quote;
'The internal hard disk drive is connected as device 0 (master) in an ATA
Device 0/1 configuration.'

'The CD-ROM drive is an ATAPI drive and is connected as device 1 (slave) in an ATA Device 0/1 configuration.'

That sure appears to me that there is only one bus. Two devices. I am regularly proved ignorant however.

ADC page: http://developer.apple.com/techpubs/hardware/Developer_Notes/Macintosh_CPUs-G3/iMac_26Oct99/index.html

Sounds fun to 'FIX' the imac though.

10-23-2001, 04:18 PM
cheers folks; all interesting stuff, esp. developer.apple.com which is a goldmine. I'm trying to find where I read on was it lowendmac or... which said rev1 g3 couldn't operate in master/slave mode, but rev2 g3s could, and I thought it mentioned the iMac as well hinting that iMacs were the same as rev2 g3s, but can I find it again, can I fup.
It does seem to be a software thing, although different chips are involved in the genesis of the iMac.
I sort of like the idea of creating some kind of Frankenstein's beast out of it anyway, so I'll try grafting into the IDE cable to try out a fast IDE CDRW, evening if it means losing the CD-ROM.
Interesting also about the Sonnet Harmoni which would fit my old rev2 with Firewire...now that was going to be my next query!
Basically I need to hone my computer architecture theory and get a schematic of the iMac, to understand it better.

10-23-2001, 06:59 PM
The hardware is all mapped out for you at ADC. Great place to start.


10-29-2001, 05:34 PM
well, I took the Plextor 24speed back home to Spain from Germany, opened up the iMac and fitted a 3way IDE cable instead of the 2way in the HD slot,fitted a 3way power cable and configured the Plextor as slave. It seems to work,in that the hard drive's IDE bus is happy with two devices on it; I've still got the Apple CD-ROM (master) alone on the 50pin ATAPI slot. I don't know how happy the Plextor is as a slave; they recommend that it should be on its own IDE slot, configured as master.