Re: rtVAX300 .. need help..

[Holm Tiffe <holm%freibergnet.de@localhost>]

Johnny Billquist wrote:

[..]
> >
> >In short: If I ask if there is an dedicated Interrupt controller in the
> >other VAXen or if it is normal that CPU REGs are mapped to Address Space,
> >then it isn't much help to read that none of the machines are water cooled.
> 
> In general I don't have much time to get involved in what you are trying 
> to do, but it would appear that you lack a little too much knowledge to 
> make much progress here.
> 
> You need to understand more and better how the VAX works, what 
> "registers" mean in different contexts, and sometimes I also wonder if 
> you might need a little more knowledge on low level stuff in general. I 
> don't know, but some of your questions might suggest this.

Aggree'd.
> 
> Just a few short comments. The VAX internal registers are not memory 
> mapped, ever. That would be against the architecture specification. 
> There are special instructions you use to access the processor internal 
> registers.

That's what I understood reading the available docs, but since I'm doing a
lot of UTSL while trying to find out how other people done with other
VAXes, there are questions come up when I read code like this:

/*      $NetBSD: vsbus.h,v 1.18 2008/03/11 05:34:02 matt Exp $ */
[..]
/*
 * Some chip addresses and constants, same on all VAXstations.
 */
#define VS_CFGTST       0x20020000      /* config register */
#define VS_REGS         0x20080000      /* Misc CPU internal regs */
#define NI_ADDR         0x20090000      /* Ethernet address */
#define DZ_CSR          0x200a0000      /* DZ11-compatible chip csr */
#define VS_CLOCK        0x200b0000      /* clock chip address */
#define SCA_REGS        0x200c0000      /* disk device addresses */
#define NI_BASE         0x200e0000      /* LANCE CSRs */
#define NI_IOSIZE       (128 * VAX_NBPG)    /* IO address size */

#define KA49_SCSIMAP    0x27000000      /* KA49 SCSI SGMAP */
/*


"Misc CPU internal regs" mapped at 0x20080000 in the address space.
I've asked about three times how this could be meant since I found nowhere
that CPU Registers are got mapped to memory addresses.
The rest of the definitions are straight forward, no question about that.


> 
> There is not an "interrupt controller". I think I've only seen such a 
> beast on PCs, and some modern embedded stuff. Interrupts are handled by 
> the CPU as a part of normal operations. As for the three internal 
> registers related to interrupts, you even listed them yourself. They are 
> (among other things) used to cause interrupts from software.

No problem with that so far.
> 
> However, there are various bus adapters, which maps addresses back and 
> forth, which can be relevant, and which you might need to understand 
> more about.
> The same goes for the MMU in general, and how buses work.

At first I'm trying to find out if I need to support some of this stuff at
all. As I wrote above I've created my own bus "rtbus" in that kernel
hierarchy since I don't want to shoot in foots that are not mine.

> 
> Sorry that I can't be of more help. The questions you ask are just going 
> to take too much time to work through. You can sit down with an existing 
> CPU implementation and start by understanding that one (the uVAX II for 
> example), and then, once you understand the details of that one, you 
> should have a pretty straight forward time of getting your board up and 
> running. If you don't have the time for those studies, I doubt you'll 
> pull this off.
> 
>       Johnny
> 

Johnny I could sit down reading manuals, searching for more manuals,
trying to learn all about the internal structures of stone age computers
until I'm old and gray (...I'm already got some grey hair, I'm 49,
getting 50 in march this year) or I can try just to ask exactly here,
where I could meet people that are knowing about this stuff, are fans of
that stuffi, with long known to me names are and hoping for some help from them.
We all here, inclusive me know that what I wan't todo is good for nothing
at all, It wouldn't save the planet or our children, I't wouldn't kick the
US people to shredder their weapons, it woudn't influence Kim Jong Un or
Ahmadinejad's opinions, nor  it will generate soe cash.
It is only fun and it pushes people from all over the world to talk togheter.

How would you decide?

Regards,

Holm
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