Re: CD-Burn: Not as green as a Brussels Sprout!

In message <43c13676$0$82662$ed2619ec@xxxxxxxxxxxxxxxxxxxxxxxxxx>
Andrew Hill <user@xxxxxxxxxxx> wrote:

> Steve Fryatt wrote:
> > On 8 Jan, Wendy Gray wrote in message
> > <6df0fde54d.Wendy@xxxxxxxxxxxx>:
> >
> >
> >>In message <43c070d7$0$82661$ed2619ec@xxxxxxxxxxxxxxxxxxxxxxxxxx>
> >> Andrew Hill <user@xxxxxxxxxxx> wrote:
> >>
> >>
> >>>That's a good point Steve. I found my SCSI setup was unreliable when
> >>>my PSU was struggling - in fact the SCSI termination is the only
> >>>thing that struggled (it was otherwise asymptomatic). Eventually I
> >>>swapped it out for a 105W PSU.
> >>>
> >>>Jutst in case you're not sure (or can't remember your GCSE physics) -
> >>>take the lid of the RISC PC. On the PSU is a yellow sticker. It's got
> >>>a number of voltages and currents. Multiply each voltage by each
> >>>current, and make the results positive. Now sum the results. It
> >>>should be either 70 or 105.
> >>
> >>Ah, thanks for that, Drew. In my ignorance I thought it was a PSU in the
> >>CD-writer we were talking about.
>
> No problem. The PSUs really should just state '70W' or '105W', but sadly
> they don't, and it does tend to cause confusion :o(.
>
> >
> > We were, sort of. I had assumed (possibly through not reading the thread
> > fully enough) that the CD Writer was in the RiscPC case and powered off
> > the RiscPC PSU. From what you've just posted, I assume that isn't
> > correct.
>
> Yeah, I'd assumed that too.
>
> >>Now, I need husband's help; the 17" Iiyama monitor is too heavy for me
> >>to safely lift off on my own. Means moving other stuff around too. In
> >>fact as a retired head of maths, he can do the calculations whilst he's
> >>at it :-) Neither of us ar physicists. If it is 70, I take it we need to
> >>upgrade (cue Chris Evans?).
> >
> >
> > It's probably not a relevant question, given that the CD Writer is in an
> > external box (it is, isn't it?). The PSU in the SCSI box may still be an
> > issue, of course; that's a lot harder to make suggestions about, though,
> > as there are many different types of box and as many different types of
> > PSU in them.
>
> Actually - the PSU output would still be an issue even if the CD writer
> is external.
>
> Firstly, since I was also under the presumption that this was an
> internal drive, let's just revisit your SCSI setup again.
>
> SCSI requires termination on each end of a chain of devices. A SCSI card
> is a device like any other SCSI device. However, normally a SCSI card
> usually has equipment to double as a terminator if it is at the end of
> the chain, which is why it's always positioned at one end of the chain
> where possible.
>
> So, in a situation where all the devices are internal, or they're all
> external, the SCSI card can act as a terminator. In many cases you have
> to switch this on or off (either using software or physically adding or
> removing the terminator packs from the card, depending upon what it is.)
> You then need a single terminator at the end of your chain of internal
> or external devices.
>
> When you've got internal AND external devices, the SCSI card is really
> sitting in the middle of a chain. The terminator should therefore be OFF
> on the card (because it's a middle device.) There should be TWO
> terminators, one at the end of the internal device chain and one at the
> end of the external device chain.
>
> It is well worth thoroughly checking this. It would be easy to have the
> SCSI card termination on or off inappropriately, or have an internal
> terminator but not an external one when you have both internal and
> external devices, etc.

We have no internal SCSI devices, so the SCSI port is the start of it all.

We only have 2 SCSI devices - a scanner and a CD writer. We only ever have
one connected at once.

When the scanner is connected, the SCSI terminator plug goes on that and it
works.

When the CD writer is connected, we plug the terminator into that. Not having
used the scanner for months, the set-up has remained with the CD writer
connected. I can't remember why the plug is in the top socket - it was either
the instrustions or 'trial and error'.

> All things considered - IDE CD writers are extremely cheap these days,
> and it may be easier just to put an IDE writer in since CDBurn accepts
> them. SCSI's great when it works, but it's a beast to set up correctly.

well to be honest, all I've done is plugged and attempted to play :-)

> Going back to the PSU issue, the problem comes with the podule bus. If
> your machine has a PC card (in particular,) a couple of podules, and one
> or two hard drives, it can easily exceed the 70W PSU's output. In these
> situations, every device has to make do with less. The thing that
> suffers first is usually the SCSI card, which doesn't have enough
> current to put through the SCSI cable. As a result, the cable often
> looks to the SCSI card as though it's terminated (intermittently) when
> it isn't - so you get sporadic errors or problems. Even if you found an
> alternative drive, if this IS the problem, then you'll still find the
> machine unreliable unless this is solved.
>
> THe reason that the PSUs are a problem are that Acorn underestimated
> just how much most people would expand their RISC PCs. Or, cynically,
> you could look at it that they wanted to sell second PSUs ;oD.
>
> Let us know what equipment you have in your RISC PC, and then some of
> the eagle-eyed here can probably work out whether a 70W PSU is adequate.

Well the machine was bought by the original owner in 1996, if dates are any
help? Oh, yes there is a PC card in the machine, I'd forgotten, but only the
one hard drive. No viewfinder cards etc. I've got a Unipod I've not yet
connected - would it be better to try to work things through that?

All this is very interesting and I'm glad I tried again even if I failed.

BTW anyone know of a reason the writer itself would reject certain brands of
disks, long before we get to the burning stage?

--
Wendy Gray, expat Yorkshirewoman
Tervuren .be

.

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