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Re: Classes incompatible with weak references
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Re: Classes incompatible with weak references


  • Subject: Re: Classes incompatible with weak references
  • From: Vincent Habchi <email@hidden>
  • Date: Thu, 16 Aug 2012 13:37:30 +0200

On 16 août 2012, at 03:11, Britt Durbrow <email@hidden> wrote:

> objects must be 16-byte aligned - and that alignment requirement isn't likely to go down, but rather up in the future; using the low bits doesn't really cause the same issue that using the high bits did.

Well, I partly disagree. There is no real difference in using MSB or LSB. At some point in the future, Intel can decide to use low bits to serve some specific hardware purpose, like signaling uncachable addresses on a fine granularity, indicating what core had fetched the pointer, or deciding at fetch time what kind of info is being accessed and route the incoming data accordingly, and so on.

> Oh, and it bit the Mac too - anybody remember the Mode32 extension from the System 7 era?

At that time I wasn’t developing on Mac, which was far too expensive for the means of a poor student. But I clearly remember having written the equivalent for the Atari TT/Falcon, MMUPATCH.BIN, a short TSR assembly code that would tinker with the MMU of the 68030 to redirect all logical addresses XXYYYYYY towards physical addresses 00YYYYYY. That was a clear kludge, but it prevented some occasional bombing ;)

Vincent



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  • Follow-Ups:
    • Re: Classes incompatible with weak references
      • From: Britt Durbrow <email@hidden>
References: 
 >Classes incompatible with weak references (From: Ben <email@hidden>)
 >Re: Classes incompatible with weak references (From: Kyle Sluder <email@hidden>)
 >Re: Classes incompatible with weak references (From: Jean-Daniel Dupas <email@hidden>)
 >Re: Classes incompatible with weak references (From: John McCall <email@hidden>)
 >Re: Classes incompatible with weak references (From: Jean-Daniel Dupas <email@hidden>)
 >Re: Classes incompatible with weak references (From: Mike Abdullah <email@hidden>)
 >Re: Classes incompatible with weak references (From: Vincent Habchi <email@hidden>)
 >Re: Classes incompatible with weak references (From: Britt Durbrow <email@hidden>)

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