On Sun, 16 Feb 2003, John Summerfield wrote:
> > There's also the fact that your cheapo-cheapo PC has one processor and has to
> > do all the I/O for itself. The PC's processor spends 90% of its time handli
> > ng I/O, formatting data for some port or the screen, running a driver program
> > , polling and waiting for a response from some peripheral and so on.
> >
>
> I don't pretend that my Athlon-based system's overall design is anything like as
> good as the S370/168 I used to use so many years ago, but fair go.
>
> My PC has the on-board EIDE interfaces (EIDE{0,1}) and additionally, an add-on
> PCI card providing two more EIDE ports.
>
> At one time I had three drives in the box on each of three interfaces. I was
> running DD to do a disk-to-disk copy, and while it was running, I used hdparm to
> test the speed of the third drive. It tested at 35 Mbytes/sec, pretty close to
> its rated speed.
>
> My graphics card has its own processor, and if I add a SCSI card that too
> offloads a decent amount of work.
>
> Devices use interrupts to signal the end of operations, and many use DMA devices
> to provide direct access to system RAM.
>
> While IBM's mainframes do all these things better (except compute), if an IA32
> system uses more than about five percent of the CPU power to drive devices, the
> OS is broken.
>
> On Linux, we use (mostly) the same software you do. It does not need lots of CPU
> power to drive most I/O devices.
I understand the benchmark results, but does that mean that current PC
could support the same workload. At John Hancock in the early 1970s a 168
supported a fairly hefty batch workload and an online inquiry system for
400+ file clerks.
If a current PC can't support that workload, what is the difference? Maybe
benchmarks don't mean that much...
john alvord
