Using it to occasionally aggregate ‘inputs’ works OK for me. I.E. To bring in a USB mic, or to ‘mix and match’ a couple of mixers with different pre-amp configurations. I.E. Sometimes I want to temporarily bring in up to 6 inputs from my Fantom XR off of a second audio device. I don’t try it at all for ‘synchronous outputs’ since there is no way I know of to force all of my audio devices to lock onto the same ‘clock’.
Occasionally I use ASIO4ALL with multiple devices to AB between my cheap computer speakers and other reference monitors/headphones on the nicer devices/speakers. Again it does OK. I don’t push it very hard in this case however…it’s just something that comes in handy in later stages of a project when I want a quick and easy way to try a mix on several different types of speakers/arrangements (by this point, most things are rendered to pure audio tracks but a few mastering level plugins).
On my rig ASIO4ALL is quite stable for the purposes mentioned above, but I don’t try to push it in terms of latency. I give it moderate to large buffers (On my rig, when working with lots of Virtual Instrument I must do this with the native ASIO drivers as well…pretty weak CPU cores on my rig).
I’m using very aged Phenom II X6 overclocked to just under 4ghz. Default speed DDR2 memory on an old motherboard, but with very tight timing. I use SATA3 Samsung SSD media through third party PCIe SATA3 cards to host my virtual instrument data/samples. Windows 10 x64 Home is my OS.
On this particular rig, when I get ‘glitches’ it’s almost ALWAYS because a core can’t keep up. The second most common cause for glitches is due to hardware interrupts at unfortunate times (the system goes fishing for data on the hard-disk, and for whatever reason, the system delays a cycle before delivering it). I either increase the buffer size, or ‘instant render’ some of the more CPU intensive tracks (Usually Virtual Instrument tracks) down to pure audio if I run into one of these issues, then I’m back in business.
With my setup, when using ASIO4ALL, I can get low enough latency to compose (play stuff in while tracking), but when it comes to fine timing and mix-downs it doesn’t always cut it. I can get it pretty close, but when precise timing is paramount, I don’t even try to do it live and by ear (with remote controls or using the mouse on the CuBase mixer with the transport going)…instead I use my eyes, and draw things directly in lanes or editors, keep listening, and judge if I need to nudge an event a bit on the time-line.
When it comes to non Stienberg hosts (Mostly Plogue Engine stuff in my case) on this particular rig, I actually get a more stable setup with ASIO4ALL with some of my more spiky plugins (Some Sonivox stuff that uses virtually no cpu most of the time, but occasionally maxes out a core when it decides to go after some new samples on disk to stream). I don’t know why, but with Sibelius and Finale on ‘this particular PC’, if I want to use the Sonnivox Orchestral Companion series of VST/i plugins, I pretty much MUST use ASIO4ALL and huge buffer sizes (3 to 4 megabyte). Something about ASIO4ALL with the Plogue Engine stuff buys the CPU enough time to get things done, where going straight to my ASIO drivers leads to glitches with the Sonnivox Plugins (even with maxed out ASIO buffers).
So…ASIO4ALL can be a very system dependent thing. CPU, Motherboard, the audio devices, media latency, the way the system’s BIOS does hard-ware interrupts…all of those things will come into play…and it’s different for pretty much every rig. For some ASIO4ALL is ‘great’ or even offers an ‘improvement’ in performance/stability. For others, it can be totally useless.