Re: [cbm4linux-users] a few questions

[Michael K. <mic...@pu...>]

Hi Ryan,

> I set up a little copying rig with d64copy, a 1541, and a XM1541 cable
> (orignally a XE1541).
>
> 1) What are the differences in operation when using warp mode?  I seem
> to get many more errors using warp mode transfers than non-warp.

Warp mode sends raw (unchecked) GCR data over the bus, leaving decoding
and checksumming to the Linux side. This is normally significantly
faster despite the fact that more data is transferred (325(?) bytes
instead of 256). Thus, the Linux host catches in fact more block
checksum errors (23) than in non-warp (turbo/original) mode, where the
1541 automatically retries and eventually succeeds.

This means also that warp is generally safer than turbo, because turbo
doesn't catch transfer errors (data sent by 1541 != data received by PC)!

> 2) Occasionally in the middle of a copy, the 1541 will bang its head
> like it encountered a read error, but d64copy doesn't report any error.
> In that case, can I be confident that a re-read succeeded?

Is that in warp or turbo? Either way, I'd say yes, the data should be
fine. If not, it's a bug ;-)

> Actually, the bigger question is, can I always trust d64copy output to
> tell me if there were any errors at all with the transfer?

Yes, see above. (Of course it doesn't hurt to repeat the copy operation
and do a binary diff, if in doubt)

> 3) Is there, or would it be possible to construct, a program to do head
> alignment of a commodore drive using a x*1541 cable and a PC?

Absolutely possible. Anything you can do from a C64 should be also
doable from a Linux PC (except highly timing-sensitive drive/host
communication stuff).
For inspiration, here's a small GTK+-based tool to measure the drives
rotation speed:

http://a98.shuttle.de/~michael/rpm1541/
(Use scratch disk!)

Cheers!

-- 
Michael

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