** 3 page feature / 2572 words **

Phenix: System Architecture

An introduction to the hardware and software evolution of Centek's powerful new computer with Shiuming Lai...

To many Atari users, the launch of the Falcon was one of the most eagerly awaited events in our computing culture. It heralded a new promise of adventure and ambition far beyond what had previously been achieved by anyone in the consumer market. Here we had a versatile machine combining rich, lifelike colour graphics, 16-bit audio capability and market-leading digital signal processor technology integration. Such qualities in an accessible package enabled the Falcon to trounce its rivals in numerous semi and fully professional applications. Certainly not least, we also craved new firepower to make bone-shaking entertainment software.

Unfortunately, it was also the ailing Atari Corporation's last personal computer before one almost equally abortive attempt to win back market share by re-entering the lucrative games arena, with its Jaguar console.

We never saw production of the rumoured Falcon040 or any other more powerful follow-up. That was a real pity because Atari's goal of a converging digital future with computers playing a central role was spot-on (without that all-important DSP chip, it would never have got as far as it has now). It was also soon becoming apparent there were serious flaws in the Falcon design. Most notably, its 32-bit central processor was squeezing data down a 16-bit bus, instantly halving its potential. To save on design and production, it also continued the ST's tradition of relying on main memory for its video frame buffer.

Since Atari's departure from computing, third party developers have become ever more inventive and resourceful. The Afterburner and CENTurbo II accelerators smashed speed limits by breaking some of the main bottlenecks in the Falcon design. Fast, replacement CPUs coupled with full-width memory. However, beyond a certain point, some fundamental features which essentially make a Falcon can no longer be easily upgraded without changing that essence. So far, no accelerator has overcome the barrier of the DSP having to access main memory through an even slower (8-bit) bus to the CPU first, although quite a few have boosted its clock speed. There has been no way of multiplying the number of DSPs available to tackle tougher tasks.

Centek of France proposed replacing the entire machine with one of similar concept but far higher performance and quality. After producing two Falcon accelerators along the way, partially to evaluate potential technologies, their work has resulted in the Phenix workstation.

Technical features of Phenix 060

We're looking at a very serious machine here, a professional design sharing characteristics with heavy duty military and industrial NC (Numerical Control) embedded computers. For example, line-filtering, self-resetting fuses and an expandable processing infrastructure.

Phenix can run with up to two 68060 CPUs clocked at 80MHz each. This processor made its d‚but in Atari circles at 50/60MHz in the Swiss, Medusa Computer's Hades TOS clone, which won acclaim for its fast implementation of the Atari TT computer model. It's a partially RISC superscalar architecture, incorporating three execution units (two integer and one floating point) giving in total an average CPI (Clocks Per Instruction) rating of 0.66, compared to 4.17 in the Falcon's 16MHz 68030. Effectively, the 68060 is able to execute several instructions per cycle, so even at the same clock speed of 16MHz its execution throughput is 6.25 times higher than the 68030.

Both of the Phenix CPUs can address the same memory locations, it's based on the centralised shared memory parallel architecture model. Centek's custom arbiter logic takes care of granting bus access.

Atari, quite rightly, made a big fuss about the Falcon's DSP. Phenix continues with the Motorola DSP56K series - to be more precise it's the DSP56301. That's where the similarity ends, for on the Phenix evaluation card, at a clock rate of 80MHz allied to 384Kbyte of 12ns local SRAM, this chip achieves a data transfer rate of 22Mbyte/s with the CENTurbo II host. On a standard Falcon with its 8-bit host port this DSP/CPU transfer rate is 3.5Mbyte/s. Phenix runs the DSP56301 at 100MHz (and one instruction per clock cycle, twice the efficiency of the DSP56001) and will accept more of the same DSPs on Centek's own PCI cards. Present indicators suggest that each card will contain another three DSPs, of course, each chip will have its own 384Kbyte SRAM for storing data sets. Best of all, at last, the DSPs can access main memory directly, and quickly - see the PCI Bus boxout.

Connectivity has changed from the Falcon in many ways. Gone is the bad old cartridge port (not buffered and liable to cause processor exceptions if physically extended in a bus-accelerated machine), RF modulator output, SCSI 2, LAN, RS-232, Centronics parallel, analogue controller input and even the MIDI. In their place we have an Ultra SCSI bus with 20Mbyte/s transfer rate. One external and one internal connector are provided for Ultra SCSI devices, the bus is auto-terminated and the SCSI chip is hot-pluggable - which means no electrical damage from live (dis)connection.

Next we have an external DSP port (like the Falcon). It is the most important link with the outside world and should please electronics designers because it carries a number of supply voltages: +3.3 (3A), +5 (3A), +12 (3A), -5 (0.5A), -12(1A) and +5 stand-by (100mA).

The additional PCI cards will also include this port, which can be used as a digital audio I/O supporting 4 input and 12 output channels through a breakout box in a similar manner to the SoundPool FA4/8 or Line Audio Jam/FAD series for the Falcon.

Centek takes the music user very seriously, as demonstrated by the flawless SDMA performance of CENTurbo II Falcons, this aspect alone having taken six months of research to perfect. Another Falcon design mistake has been rectified in the audio I/O area; in addition to 3.5mm mini-jack headphone and microphone sockets, the Phenix has proper line-level RCA connections for stereo input and output.

Last of the external connectors are two USB ports. The Universal Serial Bus is a modern high speed serial bus supporting 12Mbit/s and daisy-chaining of up to 127 devices. It features hot-plugging, meaning you can connect devices while the computer is switched on and they will be detected by the host OS which then allocates resources to drive the device. Bus power is also provided for low-drain devices such as keyboards and digitising tablets. Powered USB hubs exist, to split the USB bus and also give extra power for more demanding devices.

USB is now a maturing technology and we're seeing all sorts of peripherals from scanners and printers, to digital cameras and legacy support interfaces. Phenix will drive MIDI through one of the many USB/MIDI adaptors popular with the new G3 Macintosh machines, likewise for Centronics parallel. In both cases, USB-specific or USB-supporting peripherals are rapidly flowing onto the market.

On the motherboard there are two ATA-4 IDE connectors, each supporting two devices, including modern storage media systems Centek plans to ship with complete machines:

DVD: High capacity optical media (4.7Gbyte as opposed to 650Mbyte for CD) now popularly used as a digital video carrier for high-end home cinema systems. Identical disc dimensions to CD and sophisticated laser optics in the transport mechanisms ensure backwards compatibility with CDs as we've come to know and love.

LS-120 Super Floppy: Apple caused a stir by declaring the floppy disk dead and banishing it from the iMac onwards. Sure, 1.44Mbyte is not a lot these days, but what do you do with the hundreds of floppies carefully built up over the years? I still haven't stopped accumulating them, even since buying a CD recorder with illusions of reducing this mountain. Now I have to find storage space for piles of CD-R discs as well. Apple actually offers Zip drives as an option to its G3 tower systems (in reality a Zip disk is nothing if not just another type of floppy disk) but Centek has opted for LS-120 by Imation (3M). The media assume the same form factor as 3.5" floppy disks but pack over 100Mbyte of data with high-precision optical tracking to navigate the denser recording surface. Old-style DD and HD floppies can be read by LS-120 drives.

In terms of graphics, Phenix scorches ahead of the Falcon by using a PCI video card with 4Mbyte of dedicated video RAM. The S3 Virge DX is one of the 3D generation cards, as it has hardware texture and geometry transform processing facilities. Very colourful and detailed games with high frame rates will be possible with these features. If you prefer, you can utilise this to perform complex mechanical modelling and simulation all day long instead.

A PiNT of Dolmen Brew

Phenix is Not TOS. Centek is at pains to point out its new machine is not a TOS clone, a common assumption owing a great deal to the company's strong involvement in the Atari scene. It's certainly true that TOS is very compact and efficient compared to the mass of bloatware that some "modern" operating systems are, but it's still far from making the best of the hardware it runs on. Sluggish graphics output is the first thing most of us will think of. It also doesn't handle multiple processors, due to its underlying structure, which hasn't really changed much as operating systems go. Things we've seen in ROM-based TOS updates tended to be bugfixes, efficiency improvements and added functionality in the machine level and user interfaces.

A process scheduling manager is needed to effectively distribute the workload across processors, because not all problems are easily split into parallel computation tasks. Without scalability designed in at the start, an operating system and its applications reap no benefit from running in a multi-processor environment.

Centek's solution is a new OS called Dolmen. Unlike the OS of clones such as the Eagle, Medusa/Hades and now Milan, Dolmen is not a patched version of the TT's TOS 3.0x but a ground-up development with TOS compatibility. Confused? We've now seen how the hardware is based on a familiar architecture, so as not to completely alienate the prospective developers from the existing Atari programming base. It's the same for the system software. Lots of new concepts are being introduced but implemented and supported in a way to make the developer's life as painless as possible. See our screenshot of the Dolmen resource editor, Fashion, and the Dolmen VDI boxout. Centek's low-level debugger is another good example, it works in a very similar way to the highly regarded MonST but is multi-processor aware. Having its own OS also gives Centek complete freedom over its development.

Why Phenix?

Falcon enthusiasts will be among the first to buy a Phenix, no question about that. Centek's strategy extends further, though. Knocking the PC off its perch of general dominance is not one of them, rather, the applications where you don't want a gimmicky and unstable 200Mbyte OS (the Dolmen kernel is currently only 200Kbyte) or needs the user to be concerned with hardware interrupt settings, good mental challenge though it is. In the words of Centek, it's for those looking for something new from computing, that cherished excitement and individuality the world of PC "standardisation" has been eliminating.

Next issue, we plan to bring you a report of a first test drive of, hopefully, Phenix 060 R2. Watch this space!

** boxout 1 **
Further information

If you've found this article of interest, here are some further sources of information:

Maggie issue 27. A detailed chip-for-chip comparison between the Falcon and Phenix plus a good look at the S3 Virge DX hardware functions gives us an idea what we can look forward to from software developers. An exciting read.

http://rg.atari.org

Centek web site: Latest news and pictures, detailed technical presentation files, outline of the Phenix target markets.

http://www.centek.fr
** /boxout 1 **

** boxout 2 **
Centek memory and Phenix R2

Modern electronic design tools allow logic designs to be made and simulated on the desktop very quickly. Along with the availability of fast, dense programmable gate array chips, development of quite highly integrated circuits can be done in-house. Reasons for doing so include cost (having full-custom silicon made is an expensive business) and performance-tuning to the specific application.

Centek developed ANNA to replace the off-the-shelf RAM controller on CENTurbo II Rev. A, for Rev. B, offering significant speed advantage. ANNA is also used on Phenix 060 R1, where the local bus speed is half that of the CPU core (40/80MHz respectively). That's the reason for using EDO (Extended Data Output) RAM on the CENTurbo II and Phenix; at these bus speeds EDO achieves maximum performance in burst mode and can be picked up very cheaply second-hand since PCs are discarding EDO in favour of the newer SDRAM (Synchronous Dynamic Random Access Memory).

SDRAM doesn't give any speed advantage until bus speeds well over 40MHz. At the moment the Phenix has a local bus bandwidth of 92Mbyte/s. Centek is designing Phenix 060 R2 for the purpose of aiming to achieve 213Mbyte/s with 80MHz local bus (running the 68060s in full speed bus mode) accessing SDRAM.

The on-board Ultra SCSI is also likely to be dropped in favour of a fourth PCI socket to accommodate a SCSI card if so desired. Since ATA-4 IDE hard disks match the performance of Ultra SCSI at a fraction of the cost, higher performance will be an option. Ultra Wide SCSI uses 16-bit as opposed to 8-bit transfer, reaching 40Mbyte/s, while Ultra2 Wide SCSI delivers a healthy 80Mbyte/s, ideal for network servers.
** /boxout 2 **

** boxout 3 **
PCI Bus

PCI: Peripheral Component Interconnect. A host-independent open standard bus developed by Intel during the early '90s. Unrelated families of devices may be connected by means of "bridge" interfaces.

Phenix and Dolmen fully support PCI Bus Master mode, allowing any device on the PCI bus to take control for 132Mbyte/s burst DMA. Without PCI bus mastering, the CPU must perform all the memory transfers to and from PCI devices. This "slave mode" is exactly what happens on PCs running Windows 95/98. Only since Windows 98 have some peripherals like IDE been able to become Bus Master with special drivers.
** /boxout 3 **

** boxout 4 **
Dolmen VDI

Menhir is the name of the Dolmen VDI. Like the rest of Dolmen, it's programmed entirely in 68040 assembly language and is very fast. Here you can see a screenshot of Dolmen running TOS programs.

** BUREAU.GIF here **

Centek explained:

The VDI of Dolmen is a complete new layer that was coded by Sacha Hnatiuk and Ronan Cardaut (the graphical PCI part). It is a very modern layer like, for example, the OpenGL layer. It is also open to plug-ins from other developers.

Inside this VDI, there are many new modern OS calls/functions to allow developers to develop very quickly! But there are also all the good functions from the GEM VDI which enable backward compatibility. For example nearly all the NVDI 5 calls are included. The structure of Dolmen is modern, for example, you could plug three video cards on the PCI and the VDI will declare them as VDI devices via the PCI manager done by Ronan.
** /boxout 4 **

** Images and captions **

** P60_ARCH.GIF here **
Abstract of Phenix hardware. Ultra SCSI, DSP, USB, IDE all have PCI Bus Master capability

** FASHION.GIF **
Fashion, the resource editor for Dolmen

** PHENIXL3.JPG **
** T_PHENIX.JPG **