SCSI CF slower than IDE CF...Why?

[Sandman]

I have a CF that I can connect to my A4000 thru:

1. CF->IDE adaptor to A4000 IDE

2. CF->IDE adaptor to IDE->SCSI adaptor to WarpEngine SCSI

3. CF->IDE adaptor to IDE->SCSI adaptor to WarpEngine SCSI w/ SCSI HD on chain also.

Sysinfo reports speed of the CF fastest on #1, next #2 and slowest #3(the actual way that I want to set it up).

This seems odd.... Why does the CF on SCSI slow down the most with a real HD also attached?

Any of you experts got any ideas?

Thanks,
Tim

[ddniUK]

I am not an expert in SCSI, but I would check...

Is your scsi chain terminated properly?

Is your SCSI device set to Synchronous or Asynchronous? My BPPC SCSI is twice as fast in Synchronous mode.

[X-ray]

You got two bottlenecks, the CF adapter and the IDE to SCSI converter. That's what my guess is. You never really took IDE out of the equation.

[Damion]

Definitely check your setup, speed should be near the theoretical max of the controller (and up to the CF card transfer limit).

[Sandman]

The rating sysinfo gives for the CF card is 3.5m/sec and 8m/sec for the 10K Quantum SCSI HD even at the best setting...... I guess I was hoping for a little more.

Maybe I would just be better off hooking the CF->IDE to the motherboard IDE and putting the Quantum SCSI HD and IDE CDRW(with the IDE->SCSI adapter) to the WarpEngine.

Just going to be using the CF to transfer files to the HD anyways.

Also, Why would adding anything to the SCSI chain slow the HD down?  I am still green to SCSI in generally.

Thanks again,
Tim

[mikedouble]

Hi Sandman,

What speed does your CF card give with Sysinfo in the 3 configurations?

You will find that the SCSI bus will run at the same speed as the slowest scsi controller on the chain.

So, if your WarpEngine and IDE<>SCSI adapter have a max speed of 80Mbps, and your HD has a max speed of  40Mbps, everything will run at the slower speed. I'm not suggesting that your HD is actually the slower device, its just an example :-)

It is also possible that the buffer on your IDE<>SCSI adapter is quiet small and so doesnt handle high speed communication very well. What is the speed of your CDRom drive (ie.42x) and what kind of throughput do you get from it?

[MozzerFan]

@Sandman

In combination with a fast CF card, The CF-IDE should give you at least 7 MB/s. I can confirm what ddniUK already said. If I set my cyberscsi to asynchronous mode, it halves the speed. In synchronous mode I get ~7.5 MB/s.
This is with a scsi-ide adpter and CF-IDE adapter with a Sandisk Ultra II 4 GB CF card connected to my Cyberscsi, which is a Fast SCSI 2 controller.

[Sandman]

Ok, here is what I got.

WarpEngine set to no delay, no LUN scan, 100ns sychronous


Case#1:
Quantum 10K SCSI HD (18gb) alone on WarpEngine.....Sysinfo says 8,738,133/sec
CF Card->CF/IDE adaptor->A4000 IDE.....Sysinfo says 2,184,533/sec


Case#2:
Quantum 10K SCSI HD (18gb) on WarpEngine SCSI.....Sysinfo says 8,738,133/sec
CF Card->CF/IDE adaptor->IDE/SCSI adaptor on WarpEngine SCSI.....Sysinfo says 1,8xx,xxx/sec


Case#3:
CF Card->CF/IDE adaptor->IDE/SCSI adaptor->alone on WarpEngine.....Sysinfo says 3,276,800/sec


And I haven't thrown my CDRW into the mix yet.....

Something seems real slow here.....Arrggh! I don't which is the best way to set this all up!:madashell:

Thanks,
Tim

[ddniUK]

what happens when you give it 1 LUN? This is how my system is set up.

[orange]

I'm not sure, but changing block size might help. (if that is even possible.. there is an option for it)
The CF (at least cheap ones) are reading and writing in blocks (and that's why it does make sense to defragment  them from time to time!). if you could make the 'AmigaOS_size_of_block' same as physical, it should boost performance.

maybe I'm wrong, someone will correct me then..

[Sandman]

Thanks for all of the replies...

I know that block size for the CF is 512 and HD is 1024 thru HD toolbox.

I haven't tried switching LUN Scan from off to on... not really even sure what this is for.

I'll probably only be using the CF card for transfering files to and from the HD so maybe I should put in on the A4000 IDE anyways.  That would eliminate the A4000's boot delay also wouldn't it?

[alexh]

X-ray wrote:
You got two bottlenecks

Where?

X-ray wrote:
the CF adapter

Which is just a WIRE. Obviously no bottleneck here.

X-ray wrote:
and the IDE to SCSI converter

The Acard AEC-7720U (if he's using that) has a bandwidth of at least 20Mbyte/s which is roughly 5x that of most Amiga SCSI cards. Again no bottleneck.

There will be a latency through the IDE->SCSI so if it is transferring very small files then speed will appear slower than it really is. You need a GOOD speed test to prove it. I dunno if there are any good HD speed programs on the Amiga?

[Zac67]

You will find that the SCSI bus will run at the same speed as the slowest scsi controller on the chain.

(assuming you meant 'scsi device' rather than 'controller)

I keep reading this from time to time - it's simply not true. You can easily hook up a very slow 2x CDROM and get 20 MB/s from a fast harddrive (wide SCSI). Slow devices won't slow down the bus at all, EXCEPT
- hooking up SE devices to an LVD bus (no LVD on Amiga however)
- while they're in use; transmitting data in a slow mode (async) occupies the bus for a fairly long time, so leaves potentially less time for using a faster mode

[MozzerFan]

@sandman

Only thing I can think of is that your CF card is the culprit. What brand are you using and what speed does it have?
My Sandisk Ultra II has a read speed of 10MB/s and write speed of 9 MB/s.

[lorddef]

I dunno if there are any good HD speed programs on the Amiga?

Probably not too much point as everything is pretty slow anyway, but it'd be fun to see a port of bonnie++