Let's see.....

Auction ended August 10th.
Payment (check) sent on the 11th.
Received by seller on the 15th.
Figure it was deposited the 16th.
Should have cleared by the 21st or 22nd (depending on the bank & ours sucks at this stuff!)
Sent Priority Mail on the 24th.
Package not yet received by Sept. 1st.

Well, 7 days is not all that uncommon even for Priority packages, depending on locations involved. (2-3 days is supposedly the average, not the rule)

Before I would start the feedback war I would look to see what the shipping date was on the package when it arrives. If it was indeed sent on the 24th I don't think that you can blame the seller for anything!
If speed was an important factor of delivery of this chip I would have sent a money order in the first place. (only .80 at the PO) That alone could have saved 7-10 days in the transacion timetable.

As for the no feedback comment in the email....

Not a good move. If the chip was sent when he stated there is no reason to not leave a positive feedback. He did state that the check would have to clear
and that time varies from bank to bank.

As Michael stated, almost always all problems are caused my lack of complete communication.

Did he state in the auction how payment was to be made?
Personal checks have to clear?
Shipped same day as payment arrives?

And my personal favorite....

Did he leave a positive feedback for you when the payment cleared?
It always bugs me when a seller doesn't leave feedback as soon as payment arrives. If the buyer followed instructions and payed in a timely manner why do soooooo many sellers wait to leave feedback until the buyer does?
My feeling (and our eBay policy) is that if payment is made correctly feedback should be left right away. Not only does the buyer deserve it but it aslo lets them know that their payment has been received and the item is on the way.
If the seller is legit he should have no fear in posting feedback first. PERIOD!
Once the buyer has completed his part it's up to the seller to deliver the goods!

You may want to email the seller again if things work out.
Kindness goes much farther than threats sometimes.

(or course, if things don't work out there are always 'other ways' of handling it.............just ask my little buddy Harvey.......<BG>)