For all concerned with NetBSD/arc.

I've invested significant time to make research about NetBSD/arc and
got more concrete picture about it than ever.  I'd like to make notes
of it here.

NetBSD/arc is the worthwhile project of pursuing not only to save a
certain, now defunct, product line of MIPS processor based computers,
but also to exploit the new horizon of modern computer properties like
PCI, PCMICA and USB.  To achieve the goal forthcoming NetBSD/arc would
be, effectively, the "MIPS version of NetBSD/alpha."   NetBSD/arc would
have similar internal designs as NetBSD/alpha.  Indeed, I wrote
"mock-up" codes of possible NetBSD/arc *from scratch* to measure and
evaluate the project scope, and got surprised how much of existing
NetBSD codes are directly reusable with the "mock-up"s.  It's "a virtue
of NetBSD".

Then, speaking specifically of hardwares.  David Brownlee gave me
Millennium PC50 made by MIPS Computer System few weeks ago (Thank you,
David!).  I poked around it (and learned why they failed in market
wise)  So-called "MIPS based ARC boxes" are products targeted toward
Windows NT.  NT/mips is consisted with different designs of computers
which share processors.

[1] 'ARC chipset' machines

Acer PICA61, MIPS Magnum/Millenium, possibly some of Olivetti, the
earliest generation of NEC are belong here.  System is built around
three custom chips, which I hereby will call 'ARC chipset'.

Those who are familiar to Digital product line can see this design as
IOASIC DECstation w/ EISA in place of TURBOchannel.  Like as the other
desktop computers in the age, it share popular off-the-shelf
components, 40MHz Emulex FAS216, National DP83932.  Custom 8 channel
DMA circuit looks like IOASIC of DECstation, and I can see some
similarities with SparcStation's DMA (LSI Logic 64854).  The only one
unidentified issue is its sound circuit.  It's supportedly a 'Windows
Sound System' compatible (because it's an NT machine) built inside ARC
chipset.  Besides of it, all other hardware components can be operated
with applying existing NetBSD reusable drivers.

The framebuffer design is nearly identical to Personal DECstation
builtin.  I wrote the driver in one night with copy/modify hack of
dev/tc/xcfb.c.  Indeed, those two share 'dev/ic/ims332.h'.  The
difference is hardware registers of IMSG362 are populated in 64bit
aligned and can be manipulated with single 32bit R/W far less
annoyingly compared to Personal DECstation.  The problem is how to
handle video mode/resolution switch. 

This design has 'genuine Intel EISA chipset' consisted with 4 chips.
The challenge, if it exists ever, would be a fine controlled interrupt
masking good across ARC chipset (local bus) devices and EISA devices.
This issue could be deferred until local bus devices are well tuned.

[2] true EISA or true PCI machines

Those who are familiar to Digital product line can imagine 'Jensen', a
PC with Alpha AXP processor.  Soon this design was replaced with
then-emerging 'PCI chipsets'.  A certain models of Deskstation, NKKs
with their own PCI chipset, 2nd and 3rd generations of NEC and Semens
are belongs here.  The height of ARC NT/mips was R10000 multiprocessor
beast made by NEC, but I seriously doubt there exists a real user of it
after all given the fact of NEC secretly determined its withdrawal from
MIPS NT market earlier than the last release.


I'll report other notes as progress.  Stay tuned, folks.

Tohru Nishimura
Information Technology Centre
Nara Institute of Science and Technology