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Shuttle's XPC SN21G5 barebones system

NVIDIA's IGP comes to the XPC

ModelXPC SN21G5
Price (MSRP)$330

SHUTTLE GOT THE small form factor barebones party started way back in 2001 with the SV24. In the years that followed, the company rode the bleeding edge, integrating the latest sockets and chipsets into its evolving breadbox-sized chassis. Shuttle has slowed the pace recently, though, becoming more of system integrator than a barebones chassis provider. The breadbox remains, but Shuttle would seemingly prefer to sell complete systems to mainstream consumers than barebones units to PC enthusiasts. That's left a gaping void in the small form factor world, and we've yet to see the competition really step up to fill it.

Fortunately, Shuttle hasn't completely forgotten about do-it-yourself PC builders. In fact, the company has just launched a new addition to its small form factor barebones lineup. The XPC SN21G5 packs NVIDIA's GeForce 6100 integrated graphics chipset, a carefully massaged ICE cooler, and room for a GeForce 7800 GTX into Shuttle's proven G5 chassis.

Can the diminutive SN21G5 keep up with the latest full-sized ATX motherboards? Perhaps more importantly, how does it compare with Shuttle's last cube with integrated graphics for the Athlon 64? Keep reading to find out.

The specs
As usual, we'll kick things off with a run down the SN21G5's spec sheet. Things might look a little bare, but remember, Shuttle squeezes it all into a form factor that's roughly the size of a toaster.

CPU supportSocket 939-based Athlon 64 processors
North bridgeNVIDIA GeForce 6100
South bridgeNVIDIA nForce 410
InterconnectHyperTransport (1.6GB/s)
Expansion slots1 PCI Express x16
1 32-bit/33MHz
Memory2 184-pin DIMM sockets
Maximum of 2GB of DDR266/333/400 SDRAM
Storage I/OFloppy disk
1 channels ATA/133
2 channels Serial ATA with RAID 0, 1 support
Audio6-channel AC'97 audio via nForce 410 and Realtek ALC655 codec
Ports1 PS/2 keyboard
1 PS/2 mouse
1 Serial port
1 VGA port
USB 2.0 (2 front, 2 rear) with headers for 2 more
2 (1 front, 1 rear) Firewire via VIA VT6307

1 RJ45 10/100 via nForce 410 and Realtek 8201 PHY

1 analog front out
1 analog bass/center out
1 analog rear out
1 analog line in
1 analog headphone out (front)
1 analog mic in (front)
1 digital S/PDIF output
BIOSPhoenix AwardBIOS
Bus speedsHT: 200-300MHz in 1MHz increments
DRAM: 100, 133, 166, 200MHz
Bus dividersHT: 1x, 2x, 3x, 4x, 5x
VoltagesCPU: auto, 0.8-1.7V in 0.05V increments
DRAM: auto, 2.7-2.9V in 0.1V increments
Chipset: auto, 1.3-1.35V in 0.05V increments
MonitoringVoltage, fan status, and temperature monitoring
Fan speed controlCPU

NVIDIA's GeForce 6100 integrated graphics chipset anchors the SN21G5, giving the system DirectX 9-class graphics right out of the box. Don't expect the IGP to keep up with today's latest and greatest graphics cards, though. The GeForce 6100 has only two pixel pipelines and one vertex shader. With a 425MHz core clock speed, that doesn't make for particularly inspiring fill rates or shader crunching power. The chip's GeForce 6-series heritage should at least ensure compatibility with a wide range of games, even if they can only be run at lower resolutions and detail levels.

The GeForce 6100 is actually the lesser of NVIDIA's two integrated graphics processors, and it's missing a number of features available on the pricier GeForce 6150 IGP. Among them are an integrated TV encoder, TMDS transmitter for DVI output, support for high definition MPEG2 and WMV playback, and high-quality video scaling. Those features seem particularly appropriate for small form factor systems that are often deployed in living rooms as media-centric PCs, making Shuttle's use of the GeForce 6100 a little puzzling.

In addition to its integrated graphics processor, the GeForce 6100 north bridge comes equipped with 17 PCI Express lanes. 16 of those lanes feed the SN21G5's x16 slot, which should allow users to easily bypass the cube's integrated graphics. However, the SN21G5 lacks PCI Express x1 slots and peripherals, so the extra lane goes unused. Given the lack of PCI Express peripherals, particularly audio cards, we can't complain about Shuttle's decision to forgo a PCI Express x1 slot in favor of plain old PCI. However, the cube could use a PCI Express Gigabit Ethernet chip to bolster its networking spec.

NVIDIA usually integrates a Gigabit Ethernet controller right into its chipsets, but the SN21G5's low-end nForce 410 MCP only supports 10/100 Fast Ethernet. Shuttle doesn't include a PCI-based GigE controller, either, making the SN21G5 the first platform we've reviewed in a long, long time that's stuck at 100Mbps.

As you might expect, the nForce 410's 10/100 Ethernet controller doesn't make use of NVIDIA's ActiveArmor hardware acceleration engine. It does work with NVIDIA's firewall software, though. The nForce 410 also supports up to two Serial ATA devices, complete with 300MB/s transfer rates and Native Command Queuing. RAID support is limited to RAID 0 or 1, but in a small form factor system that can only accommodate two hard drives, that's hardly a concern.

Unfortunately, the SN21G5's basic AC'97 audio codec is a bit of a concern. The nForce 410 actually supports both AC'97 and High Definition Audio, but Shuttle has inexplicably chosen to go with the inferior AC'97. High-definition codec chips do cost a little more; however, that's money well-spent for a system with such limited upgrade capacity.