Bob Ryan
A major problem with today's fast processors is that it is increasingly difficult for I/O subsystems to keep up. As a result, a fast processor must often wait until instructions and data become available from peripheral devices such as hard drives. One solution to the problem is faster I/O interfaces.
A start-up called AdvanSys (San Jose, CA, (408) 383-9400) has developed two new SCSI-2 controller chips to help reduce the I/O bottleneck. According to AdvanSys, its ASC1000 (for VL-Bus systems) and ASC1200 (for PCI [Peripheral Component Interconnect] systems) controller chips are 2.5 times faster than other SCSI controllers. The performance figures are for I/O events handled per second, with from one to seven devices connected to the controller. Both controller chips ar
e priced at $21.95 each in quantities of 1000. The VL-Bus version is available now, with the PCI version coming in September.
AdvanSys is also selling two SCSI host adapters based on its controller chips. AdvanSCSI Gold ($599) is targeted toward servers, while AdvanSCSI Silver ($379) is meant for single-user systems. Both AdvanSCSI adapters automatically configure the I/O port address, BIOS address, and IRQ (interrupt request) channel, as well as automate the SCSI configuration.
AdvanSys chips use an I/O engine based on the company's own 10-MIPS RISC processor instead of using dedicated silicon as Adaptec and others do. Also, unlike most other SCSI controllers that feature hardware-based registers, the AdvanSys chips contain no registers. Instead, they have a high-speed connection to local memory that lets them store up to 255 I/O requests at a time, which is useful in a multitasking environment containing multiple SCSI devices. Other SCSI controllers must swap requests to system memory when the
number of requests rises above the number of registers--usually four.
The AdvanSys controller chips consist of three key components on a single die: the expansion bus interface (VL or PCI), the I/O engine, and peripheral bus interface. Having the bus interface on the controller chip reduces the chip count on the host adapter, which reduces design and implementation costs.
Illustration: AdvanSys's RISC for Disk Strategy
The modular nature of AdvanSys's SCSI controller chips lets the company marry other bus interfaces and other peripheral interfaces to the I/O engine. In the future, the same AdvanSys I/O engine may be used to support Fibre Channel, Storage System Architecture, or FireWire peripherals, in addition to SCSI.
AdvanSys Uses RISC for Faster Disks
