Front panel switches - what did they do?

Jon Elson elson at
Wed May 25 10:48:19 CDT 2016

On 05/24/2016 11:47 PM, Chuck Guzis wrote:
> On 05/24/2016 08:48 PM, Jon Elson wrote:
>> For sure!  The 360/30 was an 8 BIT machine, 8-bit memory, 8-bit data
>> paths, etc.  Really hobbled the performance, and restricted the
>> peripherals that could be attached.  The models /22 and /25 had 16-bit
>> memory and data paths.
> Do you mean the 360/20?  On the topic, were the 20 and 40 the only
> members of System 360 to use TROS?
No, the 360/20 was a 16-bit ISA, somewhat compatible with 
the 360 layout, but not really a 360.  All registers were 
16-bit, only 8 registers, lots of differences.  But, EVEN 
the 360/20 had a 16-bit memory and data paths.
The /20 had no channels, there were only 4 device types that 
could be directly attached to the built-in controllers.

The 360/30 was a full 360 implementation (16, 32-bit 
registers, floating point was available as an option), but 
the underlying hardware was 8-bit wide.

The 1130 was for a totally different market, the /20 was 
intended for very specific uses in 360 shops, and maybe as 
an entry-level "foot in the door" to move totally tab card 
shops into the 360 family.  The only /20s I ever saw were 
used as offline spool printers and card readers in large 360 


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