Hello,

* On Tue, Apr 28, 2009 at 10:21:59AM -0700 Nate Lawson wrote:
 
> The 154x series has a serial bus, which is a slower version of the IEEE
> 488 parallel bus (GPIB). In terms of protocol, they're very close (ATN,
> EOI, etc.), however the Commodore serial bus is very different in terms
> of signaling those logical conditions.
>   http://en.wikipedia.org/wiki/IEEE-488
> 
> The 1540 was an attempt to cost-reduce the PET drives while not changing
> the basic messages. They were able to get rid of one CPU and build a
> really cheap plug/cable standard. However, it would not be possible to
> handle a second drive with this design. The additional GCR decoding
> alone would exceed the CPU speed, leaving no room to do the drive
> control. Remember that these drives had to support drive-to-drive copy
> with no intervention from the PET.
> http://www.commodore.ca/manuals/commodore_1541_4040_8050_8250_comparison.htm

To be more precise: Fitting everything into one CPU was done with the
2031(LP). The 1540 just got rid of the IEEE and replaced it with the IEC
serial bus protocol. In fact, the 1540 is "almost" identical to the
2031LP.

Regards,
Spiro.

-- 
Spiro R. Trikaliotis                              http://opencbm.sf.net/
http://www.trikaliotis.net/                     http://www.viceteam.org/

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