Sorry, it is not illegal. We have a legal, compliance, trade laws, finance and related departments that deal with such things.
The buyer and supplier agree on a payment date. This is normal business. The buyer will pay when that date specified has come to pass.
Obviously, this is not even remotely close to the topic of this forum, so let's keep the accounting discussion as short as possible.
Earlier I thought you meant some creative accounting, i.e. booking the revenue whenever you want. This is illegal, obviously.
What you described now is called "instalment sale", i.e. when you recognize revenue at the moment of cash transfer. So: I sell you something for $10 and you pay me $1 every year for a decade. I report revenue of $1 every year.
Whether this is allowed or not is down to an accounting standard.
It's acceptable in US GAAP (but not mandatory!).
www.irs.gov
The other approach is when you report the whole revenue on a day of sales - even if the buyer will give you the money in the future.
So in the above example, I'd have to book $10 in first year. To offset this, I'd also book $-9 as so called
Accounts receivable, which is the money I expect to get later (it's an Asset).
It looks like AMD is not using the instalment sale method. Their GAAP and Non-GAAP revenue figures are identical. And they have very large receivables ($1.7B).
This means that the revenue we see is exactly how much CPUs they sold in a quarter and $1.7B is the cash still missing.
Precise info can be found in their financial statement, but I'm just too tired today.

I'll edit this post tomorrow.