Korg Nautilus AT — Upgrade!

Korg have announced the Nautilus AT music workstation. As the name suggests, Nautilus AT 88 and 61 have aftertouch. For some reason, the Nautilus-73 doesn’t get an AT version.

Well, of course, you can read all about it on Korg’s web site. Two points to be made here.

First, I was smacked by the first two statements on the Nautilus AT page: “NAUTILUS is KORG’s flagship workstation. The successor to the wildly popular KRONOS, …” Yep, Kronos is dead, long live Kronos. No point in pining away for a successor as Nautilus AT is it. No point wishing that Elway will return and put an end to Russell Wilson, either.

Kronos was an interesting build, being based upon a commodity Intel Atom motherboard. The weight and heat dissipation of the Kronos demonstrated the limitations of such an approach — essentially putting a mini desktop computer into a box with a keyboard. The Raspberry Pi-based models (e.g., Wavestate, OPSIX) are technologically more viable.

Second, Korg are finally doing what I’ve wished for a long time — upgrade your existing keyboard instead of discarding it:

Existing owners of 61 and 88 key NAUTILUS* need not miss out. KORG is rolling out an upgrade service that updates both the hardware and software of your keyboard, transforming your NAUTILUS into a NAUTILUS AT. For more information, and pricing of the upgrade service where you are, contact the KORG customer service team in your territory.

Let’s face it, not that much changes inside most New! Improved! synths. Usually the digital logic board is a new design, but the keyboard, display and other peripherals are largely the same.

Instead of dumping the old synth into a landfill, why not upgrade the electronics (or keybed) in the old platform?

Korg UK are somewhat ahead of the USA having a Nautilus AT Upgrade page:

Available exclusively from Korg UK to customers in the UK and Ireland, the service includes a hardware and software upgrade by a Korg service engineer alongside the collection and return of your Nautilus.

Must be nice to live on a small island. 🙂 I don’t think USA folk will get pick-up and return by a friendly Korg rep. The price quoted is £429 or about $560 USD depending upon currency fluctuations. If the hardware mod involves changing out the keybed, that’s a pretty reasonable charge.

Yamaha? Roland? Casio? Kawai? Nord? Are you watching? We are.

Copyright © 2023 Paul J. Drongowski

Why not high-end x86?

Last time around, I broke down the computational core of the Korg Kronos and Krome workstations. The Kronos is one of the few (only?) current synthesizer workstations based on the x86. The Kronos 2 is built around an Intel mini-ITX motherboard with a 1.86GHz dual-core Atom running a custom version of Linux. Since the x86+Linux combination is flexible and versatile, it hosts a wide variety of software-based synthesizers, including the ever popular sample-based synthesis used in so many other products from Korg, Roland and Yamaha (to name a few manufacturers).

Learning this, some folks may be disappointed to find a “lowly” Atom instead of high-end processor such as a honking 4.0GHz Core i7-4790K. It’s a quad-core processor (8 processing threads) with 1MB L2 cache, 8MB L3 cache, and integrated Intel HD Graphics 4600. Sounds like a positive screamer when compared against the D2550 Atom in the Kronos 2.

Before any fanbois freak out, I didn’t have any particular reason for choosing this particular CPU as the example. Yes, it was released in 2014, blah, blah.

First and foremost, please consider power consumption. The i7 is rated at 88W total power dissipation (TDP) while the Atom is rate at 10W TDP. High clock speed and high functionality come at a cost, specifically, power.

  • On the consumption side, the i7 needs a power supply with 8 times the capacity of the Atom-based solution.
  • On the dissipation side, the i7 solution needs to dissipate and remove 8 times the heat of the Atom solution.

It’s the laws of physics, folks. Silicon CMOS circuits at high clock speed consume gobs of power. If you want to save dynamic power, then reduce the clock speed and/or throw away unneeded functionality.

High power consumption and dissipation lead to difficult design problems at the product system level. The power supply (PSU) must be bigger and heavier. An ATX power supply is 2.5 to 5 pounds of dead weight. The PSU also generates heat of its own no matter how efficient it may be. CPU cooling requires both a heavy heat sink and a fan. Further, the heat produced by the heat sink and power supply must be removed from the product chassis by exhaust fans. Great, additional weight and fan noise. Ultimately, the musical instrument designer becomes a desktop computer designer.

Customers already complain about the weight of workstation products. Heavy synthesizer workstations are “studio queens.” If a workstation is too heavy to take to gigs, then why not use a high performance desktop or server solution in the studio to begin with?

One must take the CPU support infrastructure into account, too. Mid- and high-end x86 processors cannot stand alone — they need a companion chipset. The x86 processor and the chipset integrated circuit (IC) are the Mario and Luigi of computer design. You don’t see one without the other. The chipset IC implements the I/O ports: PCIe, USB and most importantly, the SATA interface to bulk storage. The chipset IC consumes and dissipates power, too, and must have its own heat sink.

x86 system design requires specialized expertise in high frequency electronics, thermal design and mechanical design. You’re unlikely to find this specific expertise at Korg, Roland and Yamaha. It’s not their core competence or value added. That’s why Korg very wisely adopted an existing mini-ITX solution for the Kronos. Korg design and manufacture the ARM-based user/audio interface board. Embedded electronics like that are a core competence and value-added component. The mini-ITX motherboard plus user/audio interface board solution is smart, system-level engineering.

So, in the end, we have the “good enough” solution that is appropriate for the product space. Korg build musical instruments, not desktop computers. The D2550 Atom has enough computational horsepower to deliver a range of synthesis techniques with adequate polyphony. The solution fits into a conventional keyboard chassis without noisy fans, without becoming dangerously hot to the touch, and at a tolerable weight.

You may think that I’ve conceded higher performance at this point, but here is one more idea for consideration — laptop technology. This solution will not deliver the absolute highest level of performance, but it might be the next step up from the mini-ITX solution. From the systems point of view, it might make sense to design a portable keyboard product around an OEM laptop motherboard, cooling system and processor. Laptop fans are generally quiet and heat could be vented through a modest port in the chassis. One could power the instrument from lithium ion batteries for relatively short periods of time or leave the batteries out for lighter weight. Perhaps Korg engineers considered this solution, too. They’ve clearly demonstrated their skill in the design of the Kronos.

Innards of Krome and Kronos

Plenty of discussion about Korg Kronos and x86 on the Keyboard Magazine forum, so it’s time to study up on Korg architecture and formulate an opinion.

Before diving in, I should say that I try to get my information from primary sources (e.g., service manuals) and to not rely on Internet “truthiness.” The Web is filled with people who want to believe something whether they are informed or not. Thanks, Stephen Colbert, for the notion of truthiness!

Not all service manuals are readily available (at no cost!), making the narrative a bit sparse. Nonetheless…

Korg have two distinct paths which have led to the current Kronos and Krome. My simplified take on the first thread of Korg workstation history is, starting from Triton:

  • Triton family begat the
  • M3 which begat the
  • M50 which begat the
  • Krome.

The second major historical thread is the multi-faceted OASYS which begat the Kronos series. Along side all of this “begatting,” Korg developed its professional arranger workstations, e.g., the PA80, PA500, etc. leading to the current PA900 and PA4x. The arranger workstations are kin to the Triton, M-series, and Krome, and share much of the underlying hardware technology.

Let’s take the Krome first because it is the most similar to Yamaha and Roland architecture.

The Korg Triton LE was released in 2002 and is a stripped down version (no sampling, no ribbon controller, smaller display, etc.) of the classic Triton. Its embedded CPU is a Renesas SH7043A, the same choice as Roland and Yamaha in that era. The embedded CPU handles all of the user interface (UI) processing and communicates with the keyboard, knobs, LCD and so forth. Samples are generated by a Korg proprietary tone generator chip designated “TGL96” or MB87F1710-PFV-G-BND. The TGL external clock frequency is 24.576MHz. The tone generator has a dedeicated memory channel to 32MBytes of wave ROM. Overall, the Triton LE internal architecture is similar to corresponding Yamaha and Roland products.

The TR61 was released in 2006 and resembles the Triton LE. It has more physical wave ROM (64 MBytes), USB-to-PC communication and an SD card slot. The embedded CPU is a Renesas SH7043A which, again, handles the UI components. The Korg proprietary tone generator chip is designated “TGL96” or MB87F170-PFV-S. Although the parts list uses the same identifier as the LE, this chip is probably just a slightly updated model in the same TGL family.

Korg marketing called its Triton-era synthesis “HI,” or “Hyper Integrated” synthesis. The PA80 arranger also uses HI synthesis and a Korg MB87F1710-PFV-S TGL96 tone generator. Thus, synths and arrangers using HI synthesis probably contain some variant of the MB87F1710 TGL family.

Skipping ahead to the M3 (released in 2007), the tone generator is designated TG01 or MB87M4080PB-GE1. Korg marketing switched to “Enhanced Definition Synthesis” or “EDS.” This chip is clocked using an external 24.576MHz crystal, yielding an internal clock speed of 98.304MHz. The TG01 has two dedicated memory channels (upper and lower PCM data bus) to wave ROM. The TG01 has a third memory channel to an 8MB DRAM for DSP working storage.

The main CPU in the M3 is a a Freescale MC9328MX1 ARM processor. The ARM is clocked at 196.608MHz. The M3 also uses a Renesas H8 (HD64F3687GFPV) for key scanning. H8s are 16-bit processors that are good for interface and “microcontrol.” The Freescale MC9328MX1 is the first appearance of an ARM processor in Korg synth. Yes, that’s right, folks. Korg have used embedded ARM processors since 2007.

The EXB-RADIAS is a synthesizer/vocoder option board for the M3 that uses Korg MMT (Multiple Modeling Technology). The EXB-RADIUS is no processing slouch, consisting of a Renesas SH7709S CPU and two Texas Instruments TMS320VC5502 DSP processors.

I located a service manual for the PA500 arranger from the same era (2007). The PA500 arranger implements EDS and contains a Korg MB87M4080PB-GE1 tone generator IC. The Freescale MC9328MX1 performs the work of a master embedded CPU (user interface, USB interface, LCD control, keyboard input, MIDI interface, etc.) The ARM core clock is 200MHz — fast enough for control, not fast enough for DSP. The DSP is handled by the MB87M4080PB tone generator.

Completing the early picture, the M50 (released 2008) is a reduced feature version of the M3. The M50 implements EDS and contains a Korg MB87M4080 tone generator.

I could not find a service manual for the Krome. Grainy images of its KLM-3119 motherboard show a Korg MB87M4080 TG01 tone generator and what is probably a TI OMAP ARM processor. Clock frequencies cannot be determined from pictures alone. The designers likely replaced the Freescale processor with the Texas Instruments OMAP. Korg marketing changed the pitch name to “EDS-X (Enhanced Definition Synthesis-eXpanded).” The meaning of “expanded” is not clear although the Krome supports more polyphony than the M50. The Krome employs an internal 4GByte micro SD card for sample storage. The TG01 appears to be driven by two ISSI IS42S16160G 256Mbit DRAMs which are organized 16Mx16bits. Very likely, samples are loaded into these DRAMs by the OMAP on demand. The SD card is relatively slow and continuous streaming from SD to the TG, to me, seems unlikely.

Up to this point in the narrative, we know that Korg have at least two generations of proprietary tone generator chip families:

MB87F1710     Hyper Integrated (HI) synthsis
MB87M4080PB   Enhanced Definition Synthesis (EDS)

Whether EDS-X represents a third generation is open to question. Summarizing further, Korg use ARM processors (low clock rate, low power) to handle UI and control tasks.

A desire for additional synthesis methods led to the Korg OASYS. The OASYS is built around the AOpen MX4GVR-GN micro-ATX motherboard (Intel Socket 478). The motherboard is fitted with an Intel 2.8GHz Pentium 4 processor and a minimum of 1GByte of RAM. The OASYS requires a fair bit of additional logic to handle all of the I/O and user interface including a Renesas H8 and a Texas Instruments embedded DSP. The operating system is a custom version of Linux.

Customers found the OASYS to be too expensive and about 3,000 were sold. Having learned from this experience, Korg developed the lower cost Kronos series. There are three major models in the series, where each model is built around a particular mini-ITX, x86 motherboard:

Kronos Lot A  Intel BLK D510M0      Intel 1.66GHz D510 dual-core Atom
Kronos Lot B  Intel D525MW          Intel 1.80GHz D525 dual-core Atom
Kronos X      Intel D525MW          Intel 1.80GHz D525 dual-core Atom
Kronos 2      ASRock IMB-140D Plus  Intel 1.86GHz D2550 dual-core Atom

The motherboard connects to an SSD memory device via SATA2 and to an ARM processor via USB. The ARM processor handles UI and interfacing duties just like the ARM processor in the Krome. The x86-based motherboard performs synthesis. Thus, the Kronos internal architecture is like the synths in the Krome line except the proprietary tone generator IC is replaced by an x86 motherboard running Linux! This internal organization gives Korg substantial cost savings over the OASYS.

According to Dan Phillips (Korg R&D), “… all synthesis, effects, and audio processing is done within the Intel CPU, and naturally the sequencer and KARMA as well.”

Two types of ARM processors were used: Texas Instruments Sitara AM1806BZWT3 (early models) and Texas Instruments AM1808BZWT3 (later models). I’ll focus on the AM1808. The AM1808 system on a chip (SOC) has an ARM926EJ-S core, 16KB I-cache, 16KB D-cache, 8KB RAM (vector table), 64KB built-in ROM (boot image), 128KB system RAM and a host of built-in interfaces (LCD, USB, SPI, etc.) The wealth of interfacing options makes this kind of ARM SOC ideal for embedded applications. The NEON signal processing extension supports 16-bit fixed point arithmetic including a single-cycle multiply-accumulate (MAC) unit. Hardware floating point is not supported. Although the NEON extension is handy, the heavy DSP is performed by the x86.

ARM core clock speed is a function of core voltage, external crystal frequency and software-level configuration. The external oscillator frequency (24MHz) and core supply voltage (1.2V) point toward a 375MHz core clock speed. In any case, the AM1808’s maximum supported speed is 456MHz. The ARM processor — unlike the high frequency dual-core Atoms — dissipates relatively little heat and does not require a heat sink and/or fan.

At this point, we have accumulated enough information to compare Krome’s synthesis hardware to the Kronos. Krome uses a Korg proprietary tone generator IC (TGL) to synthesize music. The TGL operates at a relatively low clock speed and does not require a heatsink or fan. The size and weight of the TGL are nearly negligible when compared with the mini-ITX motherboard. The Kronos x86 mini-ITX system has a big footprint (6.7in by 6.7in or 170mm by 170mm), needs a heatsink and fan, and weighs 0.61 kilograms (1.4 pounds). The heat generated by the motherboard (20 to 25 watts) must be externally ventilated, thereby complicating the mechanical design of the overall product. Thus, x86 motherboard synthesis comes with a significant system cost. The Intel chipset dissipates the most heat, so even if the extraneous motherboard components are eliminated, thermal design is a significant disadvantage of x86-based synthesis.

Here’s how the complete products stack up (61 key models):

                                    Krome    Kronos 2
                               ----------  ----------
    Synthesis                       EDS-X        HD-1
    Polyphony                      120/60         140
    Power consumption (Watts)          13          60
    Weight (pounds)                  15.9        31.5
    Weight (kilograms)                7.2        14.3

Performance is compared on the basis of sample-based synthesis while disregarding differences in tone quality. The Krome implements only sample-based synthesis, so the basis for comparison on this dimension is limited. As a complete system, the Kronos out-weighs and out-dissipates the Krome two-to-one.

Finally, here are a few words comparing Kronos SSD versus Krome Micro SD for sample storage and transfer. The Kronos SSD is SATA2 with a raw 3Gbit/sec transfer rate. Although the maximum transfer rate is 300MBytes/sec, the 30 GB Toshiba SSD (THNSNB030GBSJ) is specified at:

    Read transfer rate:  180MBytes/sec
    Write transfer rate:  50MBytes/sec

The Class 10 micro SD card is specified at:

    Read transfer rate:   10MBytes/sec
    Write transfer rate:  10MBytes/sec

According to the SD Association, these are minimum speeds and actual devices may operate faster. Further, two different SD bus speeds are rated: 12.5 MB/sec default speed and 25 MB/sec high speed. Without further testing or knowledge of the particular SD card in use, no further conclusions can be drawn properly. One should note, however, that Krome device-to-tone generator bandwidth is significantly lower than Kronos even when best SD performance is assumed.

SD device communication is simpler than SATA. SD is designed for low cost. An SD card interface is a frequent, integrated feature of an ARM SOC. The SD interface favors lower system cost and complexity.

SSD storage devices, on the other hand, are not simple devices. They contain a SATA bus controller, RAM cache and cache controller. Data caching gives SSD its speed advantage over naked flash memory. The SATA interface is part of the Intel NM10 Express Chipset IC on the Intel motherboard. Comparatively speaking, the SD card and bus win on the basis of cost and simplicity.

The complexity of the SATA interface would tend to preclude direct communication from SATA to a proprietary tone generator like the TGL. Cost and simplicity favor “raw” communication between tone generator ICs and RAM/ROM.

Whew! That’s quite a lot of detailed information. To keep things short and focused, I’ll address the suitability of x86 for conventional synthesizer design in another post.

Here is a link to my dive into some old Roland gear. You might also want to read my post about Yamaha MOX internal architecture. There are also three posts (here, here and here) about Yamaha arranger internals.