Cool Gear PCI to PCI Expansion

[Refrochia]

Thanks Valis

I did see some old posts about Magma chassis but it mentioned limitations regarding latency so would be interesting to understand exactly what the lowest possible latency is and how this compares to a more up to date solution (star tech). Hopefully Fraz can report back soon!

Looking at the Startech solution, it has physical limitation in terms of the size of the cards it will fit but if Frazs experience is generally positive then I’ll be tempted to get the cool gear solution which will fit the scope pro sized cards and report back here so we can build a full picture of what options are viable to fellow scopers. Big questions remain over how to connect the additional power cable to the IO boards though!

[valis]

Personally, I would still opt for a slightly older system to host Scope and connect it via adat etc, as I think you get a 100% stable Scope system and the ability to run your DAW machine without compromises for Scope. But since that's my path, it would make sense as my preference. Best of luck and I look forward to your report(s) on your results!

[astroman]

I also went the Adat route with an Asus P4C800 (Intel 875 chipset) and it works flawless.
5 PCI slots, Sata, IDE, AGP graphics, adjustable VCore and thus can run a Mobile P4. avoiding excessive power consumption. It‘s the most „cool“ system I ever had, with a tiny fan driven by a 5V adjustable regulator, the heatsink just gets handwarm.
It has the great PCI throughput of the 865 chipset but adds Sata. The Raid feature in Bios delays boot for a couple of seconds, but that’s not worth bothering.
Win7/SP1 was easy to install/configure. Of course not much native power, but great Scope experience.
(I‘ll get another one as spare, they pop up now and then on eBay)

[nebelfuerst]

What latency settings did you use with the cards plugged into the Magma boxes? Did you have any issues with lower buffer size settings?

Regarding the power question-the pulsar and scope cards need the old floppy drive power cable style connector plugging into the IO board-do the magma boxes have such a cable? If not what did you use for this?

I don't remember my latency settings, but there shouldn't be any issue, as it seems to be normal pci latency, maybe with half bandwidth.

My scope&pulsar are powered by pci only, there is no extra power connector.

[garyb]

no latency issues with Magmas generally, but reduced PCI capacity will be the limitation.

[Refrochia]

Hmmmm reduced bandwidth could be more of an issue for me than latency. Basically, I have 3 x A16u’s connected to 2 x scope cards for all my outboard to mix in the box.

Is the reduced bandwidth a result of the converters only supporting PCI 33mhz rather than 66mhz? I assume so given PCI-E bandwidth should be more than capable of handling the throughput of 3 x scope cards.

[garyb]

those figures can be misleading. generally, burst is measured, not sustained throughput. anyway, the problem is a timing one, because there is a PCI controller before the PCIe bus. it doesn't matter what the theoretical limits are, the real-world limit is there, i promise. the limit is not in the PCIe bus, but in the adaptor. Magma is generally the best. the cheapo ones are ok, too, but the limit is reached sooner.

[nebelfuerst]

In scope, we talk about latency of milliseconds, whereas the pci bus clocks with steps of 30ns. (.. there's µs in between )
Latency is not a topic of the bus, but of software at driver level.
The throughput/bandwidth of an expansion will half, if the adapter requires an extra 30ns cycle somewhere. (e.g. cable length)
The A16u run directly on the scope and between the scopeboards, so that shouldn't be different to a classic mainboard.
But the number of masterverbs is related to bandwidth, so their maximum number will decrease.