[rescue] emulation fun

[Dennis Boone]

 > What was the bandwidth of each of the channels on the 3090?  From a
 > least one paper, I see the figure of 402 IOPS across all the DASD, but
 > it doesn't specify the size of each IO.

I seem to recall 3 megabytes per second per channel.  Seems like we had
32 channels.  Computationally, the /200J (or was it the /180? memory
fades...) was about equivalent to an 80486.  For VM/CMS, the block size
was commonly 4k.

The impressive thing was not so much the bandwidth of one channel, as
the fact that the machine could supposedly sustain full rate across all
channels simultaneously.  Consider the main memory bandwidth needed to
achieve that while also running all the applications.

It's been ten years or more since the Multiprise 2003/205 was current.
That machine, and its relations, used arrays of pretty much garden
variety SCSI disks in their onboard storage system.

It comes down to budget.  PCs are designed to be cheap, and that crimps
the ability to engineer _everything_ to run flat out.  Mainframes tend
to have six and seven digit price tags, and customers who demand very
high reliability.

De