Re: Who has IIc ROM that allows plat 3.5" 800K drives???

[david@uow.edu.au (David Wilson)]

buggie@ben16.unm.edu (stephen e buggie) writes:
>Someone recently bragged that they have a IIC PLUS ROM chip that allows
>the _platinum_ 3.5" 800K drives to be operated on the ordinary IIC.

I find this difficult to believe.

1)	Pin 4 of the disk port is Gnd on a //c while it is 3.5* (3.5"
	disk drive select) on the //c+ and //gs.
	Pin 9 is EXTINT* on a //c while it is ENBL* (drive 2 enable)
	on a //c+.

2)	The //gs is able to run Apple 3.5" disk drives because it runs
	faster than 1MHz. The //c+ is able to run Apple 3.5" disk drives
	because of additional hardware (Multidrive Interface Glue + 2KB
	RAM chip).

At a guess, to get a //c to run an Apple 3.5 you would need to create the
3.5* signal, install a Zip chip or equivalent and then rewrite the disk
driver routines in ROM.

If it were possible, why did Apple have to add extra hardware to the //c+
(especially as it has an accelerator onboard)?
--
David Wilson  School of IT & CS, Uni of Wollongong, Australia  david@uow.edu.au