WANTED: someone to transfer IBM 5110 BASIC programs to modern PC

[Christian Corti]

On Tue, 2 Dec 2008, Fred Cisin wrote:
>> You can't just connect a 5.25"
>> drive to it. You may have a look at the 5114 MIM or the 5120 MIM (which
>> partially contains the 5114 MIM), the latter is online on my site.
>
> URL handy?

Oh, I forgot:
ftp.informatik.uni-stuttgart.de/pub/cm/ibm5110

> I never said that it would be EASY, . . .(although I did erroneously imply
> practical)

Although it would be nice, it really isn't practical. One problem is that 
the diskette controller is external, i.e. within the 5114 case, and quite 
discrete (TTL and IBM sugar cubes). This controller does FM and MFM (i.e. 
3740 and System/34 format) and is attached to the 5110 I/O bus. The 5110 
"firmware" (the Executable ROS) talks in a very basic manner to the 
controller, like "turn the erase head on *now*" or "I'm writing address 
mark bytes now, so please modify the clock pattern accordingly". Timing is 
*very* critical, there are timing loops e.g. to delay turning the erase 
head off after the last byte has been written to disk.
And the stepper control lines are controlled by software.

Attaching a 5.25" drive to this controller would be practically 
impossible, alone because of the different erase gate delays or write 
currents.

So without a 5114 (or a 5120 with internal drives) you need to make a 
controller that emulates the Diskette Interface Adapter Card accurately. 
The ROS I/O Supervisor routines are very unforgiving (I know that...)

> I've put 5.25" drives in a few machines that ran SA801 interface (with
> mixed results).  I've never done it for a drive where I would have to
> build a logic board or interface.

Practically, you would need to create your own disk interface and I/O 
Supervisor routines (which you can load into RWS).

Christian