The content of this blog is my personal opinion only. Although I am an employee - currently of Nvidia, in the past of other companies such as Iagination Technologies, MIPS, Intellectual Ventures, Intel, AMD, Motorola, and Gould - I reveal this only so that the reader may account for any possible bias I may have towards my employer's products. The statements I make here in no way represent my employer's position, nor am I authorized to speak on behalf of my employer. In fact, this posting may not even represent my personal opinion, since occasionally I play devil's advocate.

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Friday, June 05, 2020

If only we could donate platelets every 6 days rather than every 7 days

During COVID I have been trying to donate platelets every  week.   The Red Cross  requires  at least 7 days between donations.

It is a pity that this minimum spacing cannot be every 6 days. I can really only donate on weekends,  Saturday and Sunday.  But if I donate on Sunday  one weekend I cannot donate on Saturday the next week -  too close.   The only way I can  switch back to donating on Saturdays  is to miss a week. 

Does it really make that much of a difference?


Imagine that  on even weeks I can donate on Saturday but on odd weeks I can good donate on Sunday.   With the 7 day rule  the number of donations I can make is reduced by 33%,  compared to being able to donate every week  as would be allowed if the  separation were 6 days.  That's more than the 1/7th  you might  naïvely expect.

Such phenomena of quantization are common in computers. E.g. on P6 our  4 cycle FP multiplier and 3 cycle FP adder shared a pipeline.  If we had not stretched the latency of the adder  to 5 cycles we would have lost a lot  of compute bandwidth.

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