[rescue] Re: SPARC memory query

[Sheldon T. Hall]

"Gavin Hubbard" <ghub005 at xtra.co.nz> wrote ...

> <<
> On Thursday, November 28, 2002, at 02:57 PM, Jochen Kunz wrote:
> >> I would have thought synchronous memory would have far greater
> >> burst transfer rates..
> > Burst transfer rates yes, but still high latency. The question is how
> > high the sustrained data transfer rate for linear and random access is.
> > Even with modern SDRAMs you can get over 120 ns latency time (with
> > cache
> > and chip set overhead) in case of cache and page miss. The DRAM cell
> > technic didn't get that much faster in the last years. Only the
> > interface type and speed has changed.
> >
> > That is the reason why the latest 3 GHz P4 can't keep up with a "real"
> > Sun, HP 9k, RS/6k, ... in data / IO intensive load. The CPU is waiting
> > for data most of the time. "Real Machines" have the memory and IO
> > bandwith to keep the CPU bussy.
>
>    The "balance" of a design is very, very important...this is something
> that the PeeCee industry can't quite seem to figure out.
>
>          -Dave
> >>
>
> Come on Dave, be fair. I'm sure that PC designers would love to throw off
the constraints of the historical architecture - but that historical
continuity is what makes a PC a PC.
>
> But I agree, the "balance" of the design _is_ very important.

PC hardware design continuity isn't all that great, really.

Busses:    ISA -> EISA -> VESA -> PCI (with an MCA sidecar and AGP, too)
Video:     MGA -> CGA -> EGA -> VGA -> SVGA (plus PGA and XGA)
Memory:    30-pin -> 72-pin -> 168/66 -> 168/133 -> Ghod knows
(parity/non-parity, FPM/EDO, ECC)
Disks:     MFM -> pre-IDE -> IDE -> EIDE -> ATA/166 (plus SCSI in all its
variations)
Floppies:  5.25/160 -> 5.25/180 -> 5.25/360 -> 3.5/1400 (plus 3.5/1700,
etc.)
CPU:       Too many dam' "sockets" to keep track of.

They even changed the fscking serial port connectors, mouse connections, and
keyboard connections at one time or another.

What makes a PC a PC is that it's cheap and conforms to the PC "standards"
of the day.  Unfortunately, those "standards" have generally been determined
by cost rather than utility, and with little view of the future.  They
change frequently, too.

IBM's original marketing plan for the PC envisioned sales of "up 25,000
units."  They weren't too concerned with the long haul, since periodic
replacement of small systems (remember the 5110?) was the way they did
business.

-Shel