WE‘RE STILL WAITING for the USB 3.0 host controller “war” to start, but after speaking with Renesas at TFE 2010 it looks like the company is already preparing for what will come. We also confirmed that Renesas is indeed working with AMD to help implement USB 3.0 support in its future chipsets.
Renesas current µPD720200A USB 3.0 host controller is a 10x10mm FPBGA chip, but its two upcoming models will use different packaging and both will be a fair bit smaller. The first of the two new host controllers will be a two port solution just like the µPD720200A but it will measure 7x7mm and we were told it’ll use significantly less power at idle and standby. The second solution is a four port USB 3.0 host controller, something that many of the motherboard manufacturers are still waiting for and something that only VIA and Texas Instruments have announced so far, but neither have delivered.
Digging a little bit deeper we were told that Renesas four port USB 3.0 controller will only use a single PCI Express lane, as apparently the company has been pressured by the motherboard manufacturers to keep the cost as low as possible. By using a single PCI Express lane Renesas could reduce the price by about 50 cents per chip and it would also end up running cooler. The four port host controller will measure 8x8mm and it could potentially be the first USB-IF certified four port USB 3.0 host controller unless VIA gets their VLI VL800 host controller certified first.
In all fairness, both the VL800 and the upcoming TUSB7340 from TI are both single lane PCI Express Gen II, just like Renesas upcoming solutions. This shouldn’t prove to be too much of an issue with any current USB 3.0 devices, as nothing will come close to reaching the 5GBit/s theoretical limit of USB 3.0. A single PCI Express Gen II lane can handle 4GBit/s which is close to the raw throughput of USB 3.0, so even for a single, very fast device this is enough bandwidth, but don’t expect to get full speed performance out of four devices connected to the upcoming four port USB 3.0 host controllers for now. We were also told that due to chipset interconnect bandwidth limitations in most consumer chipsets, it doesn’t make a lot of sense using more bandwidth for USB 3.0 unless some changes are made to the chipset interconnect to offer more bandwidth.
As to Renesas involvement with AMD, the company is helping out on both the software and hardware implementation sides and they are indeed working on a four port solution here. Renesas was hoping for Microsoft to offer a standard USB 3.0 stack for Windows, but doesn’t expect this to realistically happen until the next version of Windows comes out. This means that we’ll have to rely on third party stacks for quite some time to come, something which could still cause certain interoperability issues, although Renesas said that they’re working actively to solve any device interoperability issues that crop up over time, be it with USB 3.0 or USB 2.0 devices.S|A
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