🚀 go-pugleaf

medcalf@ppc5.svo.dfw.ibm.com (Jeff Medcalf (214) 280-5970 IBM SDO) writes:

>In article <DCJun2.7ns@wombat.hanse.de>, root@wombat.hanse.de (Bernd "Bernie" Meyer) writes:
>> medcalf@ppc5.svo.dfw.ibm.com (Jeff Medcalf (214) 280-5970 IBM SDO) writes:

[SCSI functions "left out" from some PC SCSI cards...]

>> >Boot from a device connected to that card
>> 
>> Only a BIOS limitation, and nothing to do with SCSI compatibility.

>True, but irrelevant.  The measure of the usefulness of a SCSI card is
>whether or not it can do what you want.  If it has a bad BIOS, then it
>is not useful in some (many) cases.  The point of the post by Frere was
>that SCSI on the PC is not the given that it is on the Mac (and, I presume
>from my brother's experience the Amiga as well).

The point of the post by Frere was that he could take his disk and walk over
to any other Mac and just plug it in, and have it show up on the desktop. 
To which someone (I think not me) responded that this works as well with 
SCSI equpipped PCs. I don't think not booting from an SCSI device would be a
big problem in this regard. Booting, also, isn't an "SCSI function". If
there is nothing else to boot from, that would be a pretty strange PC,
right? If there _is_ something else, no magic by the SCSI host controller
can override that WD-compatible boot. So the PC can obviously boot from
something, and adding an SCSI device won't take that ability away, right?

>> >Co-exist with other boot devices (such as an IDE controller or another
>> >  SCSI card)
>> 
>> The same.

>See above.

Have you _really_ seen an SCSI card that wouldn't coexist with an IDE card?
I doubt that, really.

>> >Handle anything *except* a scanner of a particular brand
>> 
>> This, however, is most likely a problem of the scanner.

>The scanner and card were tuned for each other, and neither would support
>anything else.  Also see above.

Then that is not an SCSI equipped PC, but a PC with a proprietary scanner on
a proprietary interface, which somehow resembles SCSI. My Mitsumi interface
looks a lot like IDE, too, but still I can't connect a harddisk to it.

>> >Support more than two devices
>> 
>> Nonsense. That's a BIOS problem. 

>And drivers and DOS and a few other things.  But yet again, see above.

Exactly. DOS has no concept of more than two harddisks (there is no 2
devices limit on any card I know, but a two harddisks one). So how would you
expect the SCSI card to overcome this? Run something which has a decent set
of drivers, and you are fine. I am really sick of everybody equating
PC=DOS+WINDOWS

>> >Support more than one IRQ setting on the card
>> 
>> Which doesn't really pose any SCSI compatibility problems, right? "Leaving
>> out SCSI functions" is what we were talking about.

>It's a semantic arguement.  I'm not talking about the signals used on the
>cabling of the SCSI chain, sent between devices.  I am talking about what
>the cards can or cannot do.  If a card cannot support more than one IRQ,
>that is a problem.  The whole point is that PC SCSI cards are quite
>often dismal, even when coming from well-known and generally good SCSI
>card vendors.

Still, an "SCSI equipped PC" will probably not get into serious trouble when
you add another device to the SCSI bus just because the SCSI controller
supports only one IRQ, right? If you want to talk about getting to the point
of having an "SCSI equipped PC", we might share some bad experiences. But
then, getting a Mac might be a bad experience as well :-)

>> I think you are speaking about stupid BIOS and DOS extensions. And what the
>> ^%^*^^&* is an SCSI drive "larger than 1024 sectors"?  Even under DOS, such
>> a thing does not exist.

>Pardon?  I am very confused by your statement that drives with more than
>1024 sectors do not exist, since I have used quite a few of them.

An SCSI drive doesn't have heads, cylinders and sectors (BTW: Show me a
drive with more than 1024 sectors per track, and I'll be impressed. I think
they are currently at around 100 sectors/track, with many many tracks). An
SCSI disk device is a collection of consecutive blocks, numbered from 0 to
N-1. 
Of course, the host adaptor has to faake something for DOS, which means it
invents some numbers for heads, sectors and cylinders. But as the host
adaptor catches the BIOS calls, it is not hindered by compatibility to an
age old WD chipset, and can thus easily access any harddisk of up to 4G
(that's how much DOS can handle, BTW).

>> >Further, I've never seen a PC SCSI card/
>> >driver combination that allows one to boot from a device with a non-0
>> >SCSI ID.  This prevents, for example, hooking a known good hard drive
>> >to the machine externally in order to diagnose problems with the machine.
>> 
>> I have seen many that simply boot from the _first_ found device. If you put
>> your internal harddisk on ID 4, what you want to do is easy.

>I left out the words "on DOS/Windows."  With OS/2 or Linux, I don't think
>that the ID is significant.  It is when working under DOS.

Nonsense. Booting is a thing that happens _before_ the OS runs. And after
the OS runs, disks are only handled through symbolic names (or table
entries, BIOS calls, or whatever), not through IDs. Every host adaptor that
will find a disk at ID 4 at all will also give you access to it in DOS and
Windows.

>> You haven't mentioned a single SCSI function that might be missing from
>> PC-SCSI host adaptors that makes connecting your devices to it difficult. Of
>> course, some SCSI adaptors don't implement synchronous operation, some don't
>> provide disconnect/reconnect, most can't act as a target. But
>> 
>> a) None of this is needed to connect an SCSI device, and
>> b) None of this is guaranteed to be available on either Mac or Amiga.

>Again, that is not what I was talking about.  I was talking about how
>in general the "cut any corner" mentality in the PC market has resulted
>in a large number of SCSI cards (and others, really) which are absolute
>crap.  And in fact, because of the way that Macs are designed and built,
>and because of the quality standards in the Mac market, I have never seen
>a single Mac or add-on Mac SCSI card which had any of the problems that
>I mentioned in regards to PC SCSI cards that I have seen.

We needn't argue that there is a lot of crap out for PCs, and that
especially the combination of second-thought addition SCSI and
not-a-single-thought DOS is problematiic to get to work. But I strongly
disagree with your statement that, once you have managed to do that, simply
plugging in another device will potentially get you into a lot of trouble.

Bernie

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Anybody out there who knows how to connect a Wyse terminal keyboard to a PC
_without_ the terminal in between? Current keyboard lses chracters evr so
oftn.............  Getng wrs al te im. Hp!