Re: Yes, NetBSD still boots on pretty ancient Alphas...

Hello Jason,

Nice catch :) and thanks for the good explanation!

So I have built the current sources and...

DEC 2000 Model 300 AXP - ROM Version 2.2

Copyright (c) 1993 Digital Equipment Corporation.

Alpha AXP SRM Firmware Version - 370
VMS PAL X5.48/OSF PAL X1.35 - Built on 12-FEB-1996 13:08:14.13

Eisa Info       Devnam      Devstat
---------       ------      -------
               CPU         OK EV4 P3.0 6.6ns
               MEM         OK 64MB
               NVR         OK
               SCC         OK
               IT          OK
               KBD         OK
               LPT         OK
1 CPQ3111       VGA         OK
2
3 ADP0001       SCSI        OK
4 DEC4220       NI          OK 08-00-2B-3D-48-F1
5
6 ADP0002       SCSI        OK

>>> sho dev

BOOTDEV      ADDR      DEVTYPE    RM/FX    DEVNAM      REV     NUMBYTES
-------      ----      -------    -----    ------      ---     --------
ERA0         08-00-2B-3D-48-F1
DVA0         PC Floppy DISK       RM
SCSI Devices..
HOST         A/7/0     PROC                AHA1740A    G.2
DKB0         B/0/0     DISK       FX       RZ28        D41C      2.10GB
DKB100       B/1/0     DISK       FX       RZ28        441C      2.10GB
DKB200       B/2/0     DISK       FX       RZ28M       0568      2.10GB
DKB400       B/4/0     RODISK     RM       RRD46       1337    ......
HOST         B/7/0     PROC                AHA1742A    G.2

>>> b dkb400
INIT-S-CPU...
AUDIT_BOOT_STARTS ...
AUDIT_CHECKSUM_GOOD
AUDIT_LOAD_BEGINS
AUDIT_LOAD_DONE

NetBSD/alpha 9.99.87 ustar Bootstrap, Revision 1.3 (Sun Jul 25 17:15:20 UTC 2021)

VMS PAL rev: 0x100010530
OSF PAL rev: 0x20123
Switch to OSF PAL code succeeded.

Boot flags: 0,0
11176544+185088=0xad5da0

Entering netbsd at 0xfffffc0000a01410...
[   1.0000000] Unrecognized boot flag '0'.
[   1.0000000] Unrecognized boot flag ','.
[   1.0000000] Unrecognized boot flag '0'.
[   1.0000000] Copyright (c) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
[   1.0000000]     2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017,
[   1.0000000]     2018, 2019, 2020, 2021 The NetBSD Foundation, Inc. All rights reserved.
[   1.0000000] Copyright (c) 1982, 1986, 1989, 1991, 1993
[   1.0000000]     The Regents of the University of California. All rights reserved.

[   1.0000000] NetBSD 9.99.87 (INSTALL) #1: Sun Jul 25 19:26:16 CEST 2021
[   1.0000000] igyenes@thinkpad:/mnt/netbsd/alphaobj/sys/arch/alpha/compile/INSTALL
[   1.0000000] DEC2000 model 300, 150MHz, s/n
[   1.0000000] 8192 byte page size, 1 processor.
[   1.0000000] total memory = 65536 KB
[   1.0000000] (2048 KB reserved for PROM, 63488 KB used by NetBSD)
[   1.0000000] avail memory = 51288 KB
[   1.0000000] mainbus0 (root)
[   1.0000000] cpu0 at mainbus0: ID 0 (primary), 21064-0 (EV4)
[   1.0000000] jensenio0 at mainbus0
[   1.0000000] pckbc0 at jensenio0 port 0x60
[   1.0000000] com0 at jensenio0 port 0x3f8: ns8250 or ns16450, no fifo
[   1.0000000] com0: console
[   1.0000000] com0: interrupting at vector 0x900
[   1.0000000] com1 at jensenio0 port 0x2f8: ns8250 or ns16450, no fifo
[   1.0000000] com1: interrupting at vector 0x920
[   1.0000000] lpt0 at jensenio0 port 0x3bc
[   1.0000000] lpt0: interrupting at eisa irq 1
[   1.0000000] mcclock0 at jensenio0 port 0x170: mc146818 compatible time-of-day clock
[   1.0000000] eisa0 at jensenio0
[   1.0000000] device CPQ3111 at eisa0 slot 1 not configured
[   1.0000000] ahb0 at eisa0 slot 3: Adaptec AHA-1740A SCSI
[   1.0000000] ahb0: interrupting at eisa irq 12 (edge trigger)
[   1.0000000] scsibus0 at ahb0: 8 targets, 8 luns per target
[   1.0000000] depca2 at eisa0 slot 4: DEC DE422 Ethernet
[   1.0000000] depca2: shared memory at 0xd0000-0xdffff
[   1.0000000] le0 at depca2
[   1.0000000] le0: failed to clear memory at 0 (0xff != 0xaa)
[   1.0000000] ahb1 at eisa0 slot 6: Adaptec AHA-1742A SCSI
[   1.0000000] ahb1: interrupting at eisa irq 14 (edge trigger)
[   1.0000000] scsibus1 at ahb1: 8 targets, 8 luns per target
[   1.0000000] isa0 at jensenio0
[   1.0000000] vga0 at isa0 port 0x3b0-0x3df iomem 0xa0000-0xbffff
[   1.0000000] wsdisplay0 at vga0 (kbdmux ignored)
[   1.0000000] fdc0 at isa0 port 0x3f0-0x3f7 irq 6 drq 2
[   1.0000000] entropy: WARNING: extracting entropy too early
[   1.0053666] scsibus0: waiting 2 seconds for devices to settle...
[   1.0763652] scsibus1: waiting 2 seconds for devices to settle...
[   3.3998922] fd0 at fdc0 drive 0: 1.44MB, 80 cyl, 2 head, 18 sec
[   4.9155283] sd0 at scsibus1 target 0 lun 0: <DEC, RZ28     (C) DEC, D41C> disk fixed
[   5.0112145] sd0: 2007 MB, 3045 cyl, 16 head, 84 sec, 512 bytes/sect x 4110480 sectors
[   5.1176768] sd1 at scsibus1 target 1 lun 0: <DEC, RZ28     (C) DEC, 441C> disk fixed
[   5.2133648] sd1: 2007 MB, 3045 cyl, 16 head, 84 sec, 512 bytes/sect x 4110480 sectors
[   5.3178716] sd2 at scsibus1 target 2 lun 0: <DEC, RZ28M    (C) DEC, 0568> disk fixed
[   5.4194330] sd2: 2007 MB, 3045 cyl, 16 head, 84 sec, 512 bytes/sect x 4110480 sectors
[   5.7719750] cd0 at scsibus1 target 4 lun 0: <DEC, RRD46   (C) DEC, 1337> cdrom removable
[   6.4770424] WARNING: 2 errors while detecting hardware; check system log.
[   6.7016639] root on md0a dumps on md0b
[   6.7465883] root file system type: ffs
[   6.7905274] kern.module.path=/stand/alpha/9.99.87/modules
[   6.8549961] WARNING: preposterous TOD clock time
[   6.9101580] WARNING: using filesystem time
[   6.9591224] WARNING: CHECK AND RESET THE DATE!
Terminal type? [vt100]

Have to tried to istall but will do hopefully tomorrow!

Thanks again,

istvan

On Sat, Jul 24, 2021 at 5:23 PM Jason Thorpe <thorpej%me.com@localhost> wrote:

> On Jul 24, 2021, at 7:51 AM, Jason Thorpe <thorpej%me.com@localhost> wrote:
>
> Anyway, I’m almost convinced it’s something to do with how we’re configuring the SCSI controller. I’m doing a little more investigation today and hopefully will have something to try out in a little while.

Ok, let me explain what I mean here.

There are two types interrupt triggers on EISA… edge trigger and level trigger.

With edge trigger, the PIC detects the interrupt on the RISING EDGE (i.e. transition from low-to-high) of the interrupt line.

With level trigger, the PIC detects the interrupt so long as the interrupt line is driven low (i.e. the line has a pull-up resistor enabled in this mode, and the interrupt lines on the devices are open-drain).

Our “ahb” driver is always registering the interrupt handler as level triggered.

The 1740 controller has a configuration register for its interrupts, INTDEF, where we can read the IRQ that it’s configured to use (we could also read this from the ECU data on Alpha, and I would like to enhance the driver to do that, but that can wait for another day). One of the bits in that register is called INTHIGH. There is a comment in the ahbreg.h file:

#define INTHIGH 0x08 /* int high=ACTIVE (else edge) */

I believe this comment is **incorrect**. Well, *partially* incorrect. I do believe it means “IRQ signal is active-high”, but as I have explained above, active-high (well, transition from low-to-high) is how edge triggered interrupts work, so “else edge” doesn’t make sense… what that really should say is “else level”. I double-checked what Linux does with this bit, and while they don’t define a name for it, their driver treats this bit as "edge trigger".

So, what I think is that the firmware has configured the SCSI controller for an active-high (i.e. “edge triggered”) interrupt, which tells the microcontroller on the card to hold the interrupt line low. But we’re registering the handler as “level triggered”, and thus causing the PIC to be programmed to signal an interrupt so long as that line is low.

Remember how there was previously evidence of an interrupt storm? :-)

-- thorpej