M1 iMac Pre-Purchase Planning

M1 iMac stock image courtesy of Apple.

I expect Apple Silicon to have a major impact on the functionality of the iMac. The addition of the custom rendering and custom machine learning hardware resources places the desktop Macs on par with the iPads and iPhones opening possibilities for audio and video processing on the new products. So I decided to be an early adopter while my 2017 iMac had some trade-in value.

In this post, I’ll talk about some things to consider in the pre-purchase planning phase.

References

How Big a Display do You Need?

One nice thing about iMacs is that Apple sells you a nice display into which it has built a nice computer. The new M1 iMac has a 24 inch 4.5 K Retina display. This is a good size for photo and video editing. Over in accessibility you can tailor scaling and font selection to keep things readable. I like to have enough display to keep my work and a related reference web page side by side. If you’re a developer, this is a good working model as library API references are in constant use.

There’s only one choice today but Apple has made a nice one. The stock display is about 4 times the area of a laptop display. I don’t use laptops because I don’t like the display experience!

How much main memory do you need?

Perhaps the easiest thing is to begin your typical work flow, open Activity Monitor, select the memory tab, sort by Memory decreasing, and look at the totals below and the memory intensive processes. Here ClamAV for MacOS is the top dog with over 1 GB allocated. So, for day to day use, 8 GB is fine. If you expect to be working with a DAW or a video editor, select 16 GB.

DaVinci Resolve 17 wants about 1.5 GB with about 2 minutes of iPhone video loaded. It goes up from there quickly as more clips are opened and added to the timeline. Most non-linear editors cache clips near the play head (edit point) in memory.

Also take a good look at your menu bar background widgets. Clam AV has a gigabyte wired. Gemini II has almost as much allocated. Its duplicates monitor was launched at login. Clam AV disk scanning has a chunk also. Some of these things, like Gemini II, can be disabled in preferences. Also, in my experience, frequent anti-virus patrols are not needed but external disk scanning is wise when sneaker-netting media or work products about.

It appears, Luminar Ai wants memory! Luminar grabbed 6.2 gigabytes of main storage. I knew there was a reason to get the larger memory configuration.

How big is your digital shoebox?

The Dismal Manor Digital Shoebox is pretty big. I have 20 years of photos and video in my Photos library and 20 years of ripped disks in my Roon library over on the TrueNAS 12.

So, I have used about 1 TB of a 2 TB fusion drive on Trey, my legacy 27 inch iMac. Looking at the M1 iMac configurator, I need 2 TB of internal storage (ouch).

Plenty of room here. Dismal has our Roon music library plus our Time Machine spool volume. This stuff is on a TrueNAS server because it has a network interface that Apple will be challenged to disappear although I suspect they are trying to move from boring radio waves to quantum entangled pair communications.

MacOS shows the system’s directly connected storage on the storage tab. Storage devices also appear in the USB or Thunderbolt tabs. This Glyph Disk is USB 3 capable and comes with a USB C passive cable. It appears as a USB 3 device in the USB hierarchy. The device details show that it is storage. The device also appears in the storage summary tab.

USB and Thunderbolt Ports

The new iMac (it’s not had a naming, maybe Head Honcho to keep with the well known greyhounds theme) has 2 USB 4 ports and 2 Thunderbolt 4 ports both with USB C connectors.

I use USB ports for the following things.

Charge mouse, keyboard, and touch pad.
Use keyboard and touch pad while they are charging.
Scan from the Epson printer.
Printing is by the network daemon built into the printer.
Transfer photos from the good still camera.
Charge iThings and back them up.
Schlep audio and video between church and home.

Fortunately, my needs are modest mostly. Common USB device classes satisfy all of these use cases and an iPad charger covers about half of them.

Apple Insider [10] does an excellent job explaining the evolution of USB and Thunderbolt and the convergence of the two with the introduction of the USB C connector and USB 3.2 physical layer and link layer.

Apple has general guidance in Reference [8] but cautions to check model-specific guidance. In general, USB C ports labeled USB support the USB 3.2 physical layer, link layer, and USB device classes. When Apple labels a USB C port with the Thunderbolt symbol, it is capable of both USB 3.2 and Thunderbolt service.

First, allocate the Thunderbolt ports to Thunderbolt devices such as fast external storage, video input, audio input, and video output. If you are using a Thunderbolt Dock, it would connect to one of these two ports.

Second, allocate the USB ports. I have a local USB 3.2 hub that I use with the keyboards, mice, and touchpad, USB audio devices, and USB storage devices.

The Apple Insider article [9] does an excellent job explaining the cable requirements of USB C and Thunderbolt 3 including length limitations and where active cables are required and how to keep all the cable variants straight.

Audio Interfaces

Live production digital audio (digital mixers and their stage boxes) has dramatically changed music production and film audio production. Equipment from live world (performance) rivals studio world (recording) equipment in capability and audio quality. An analog mix desk, external microphone preamps, external equalization, and external effects are no longer necessary. Live world stage boxes provide basic pre-amplification and equalization while mixer and DAW channel plug-ins emulate favored classical analog effects processors.

Live world went digital because digital stage boxes allowed elimination of the hum prone analog “snake” (size of an anaconda) that connected the stage ports to the microphone preamps in the control room. In a touring environment, load-in and load-out bruised the snake causing it to become noisy and to develop open channels. So live sound vendors did their best to replace the snake with an Ethernet cable.

After pioneering manufacturers established the general approach to digital audio, Audio Engineering Society gathered the vendors together to consolidate the core capabilities into the AES-67 standard. Manufacturers are free to extend the standard but, as in networking, they quickly realized that it was to everybody’s advantage to have mix desks and stage boxes interoperate and mix desks and digital audio workstations like Logic X and ProTools interoperate with the mix desks and their stage boxes.

The beauty of AES-67 is that it allows the DAW host to interact with a large number of audio channels over its networking interfaces. AES-67 replaces proprietary audio interface bus interfaces with standard IP networking ports. This greatly reduces the cost of a production system or playback system.

AES-67 and Midi are the key interoperability technologies. AES-67 abstracts several standards including Dante and Ravenna. Both support the IP network layer and UDP transport layer allowing routing and switching. Earlier attempts building directly on the Ethernet Link layer are not generally interoperable and could be switched but not IP routed.

Dante and Ravenna support large scale systems with Ravenna finding use in film scoring and in large scale content delivery within entertainment venues. Dante finds wide scale use within live sound performance.

Allen and Heath and Merging Technologies offer AES-67 capable stage boxes with A&H favoring the Dante AES-67 flavor and Merging favoring the Ravenna AES-67 standard. You’ll need the vendor’s app to configure the stage box channel strips and system but once set up, your AES-67 capable DAW or mixer can use their inputs and outputs.

Reference [11] explains Dante basics including use of an application to patch sources to destinations and to establish audio devices for each path. The DAW shows these as audio inputs and audio outputs. Within the DAW or mixer, the inputs are patched to tracks and track outputs to mix buses or effects buses. The buses are then routed to Dante outputs.

Review your digital mixer or digital audio interface user guide to determine how it provides audio devices and interacts with your digital audio workstation. In most cases, USB and Thunderbolt interfaces can continue to be used with the proper USB C to USB cable. Network devices can continue to be used with the proper AES-67 support software for Dante or Ravenna variants.

Video Interfaces

The new iMac supports display port over USB or Thunderbolt. MacOS will query the connected device to determine the device classes that it supports and will create the proper devices and load the appropriate class drivers for the device. This is all pretty transparent to the user. Thus, using the proper port adapter, it is easy to support a second video output or to accept video input. But, today, it is one port per video stream in or out for the M1 iMac. Later Macs may have different capabilities and limitations.

Depending on your switcher, you may need to go from USB/Thunderbolt to HDMI in or out or to SDI in or out. A number of vendors including Black Magic design make high quality interfaces for use with USB/Thunderbolt ports. Again, review user guides for USB C and Thunderbolt connection.

Thunderbolt 3 devices can be daisy chained, For example, a Thunderbolt 3 port can serve one or more external displays but the more part is product specific on Apple’s end. The M1 iMac supports one display port device on either the USB or Thunderbolt ports.

Video inputs are commonly Thunderbolt 3 devices. Black Magic Design seems to think so as its switcher user guides recommend only Thunderbolt ports when returning video to a computer for capture or streaming.

However USB cameras are known to work properly and many Black Magic Design devices emulate a camera on their USB Type B port. Which to use depends largely on simultaneous activity and distance. Again, review the use cases in the device user guide.