Here is the winchester motherboard Xbox 360 e Stress Test Kit or Prototype Console but its the Xbox 360 e. thanks to for the pic This motherboard only has 512mb ram no 1gb mode
It's an E, awesome find btw. I wants.... pm me if you're interested in parting with it. Here's a retail for comparison
Looks like they were too aggressive with the cost cutting - that production board has substantially more components on in than the test one did. They all seem to be power supply upgrades (larger diodes, extra filter caps, what looks like a complete additional switching regulator at one corner of the board and that complex with the big ferrite, 6 added diodes and a row of filter caps next to the CGPU. That's quite unusual - normally the engineering models have more parts than the production ones and they work out which ones you can lose during testing.
