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Software News : Release of onchipmem.resource AmigaOS 4.1 component for Sam460ex
Posted by m3x on 2013/2/24 18:50:00 (1592 reads) News by the same author
Software News

ACube Systems announces the immediate release of the onchipmem.resource.
This is an OS4 component that provides access to the On Chip Memory (OCM) found on the APM460Ex SoC (used on the Sam460ex board for example).


The OCM buffer is 64KB in size, 128-bit bus width, and is much faster than main RAM, up to double the DDR2 speed, basically it has a speed similar to the 460Ex L2 cache.

It's main use is to store often accessed application data, or as a way to transfer more quickly a data buffer to/from video ram for example.

The archive contains documentation and example source code on how to use this resource.

The archive onchipmem_res.lha is available on OS4depot) (currently in upload queue) or on ACube Systems web site


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Author Thread
Chris
Published: 2013/2/25 19:11  Updated: 2013/2/25 20:14
Amigans Defender
Joined: 11/17/2006
From: England
Comments: 3293
 Re: Release of onchipmem.resource AmigaOS 4.1 component f...
I was hoping this would have an AllocOnChipMem() function so it could work identically to main memory (perhaps with an ISONCHIPMEM macro to make it easy to identify which memory freeing function to use - as I'd intend to failover to main RAM).

Unfortunately, it looks like the entire 64KB has to be obtained and then manually micro-managed, which makes it somewhat more difficult to utilise effectively.

I have a little library that could potentially benefit from being able to use this speedy memory too. (edit: actually, it might benefit from a slightly different usage than I originally envisaged... let's see!)
m3x
Published: 2013/2/26 14:20  Updated: 2013/2/26 14:20
Just popping in
Joined: 12/01/2006
From: Anzio (Rome), Italy
Comments: 115
 Re: Release of onchipmem.resource AmigaOS 4.1 component f...
@Chris

to me it seems overkill to implement a whole "alloc / free" functionality for just a 64 KB block, but if there is a real demand for such feature, I'll look into it.
corto
Published: 2013/2/26 19:04  Updated: 2013/2/26 19:04
Not too shy to talk
Joined: 03/30/2007
From:
Comments: 296
 Re: Release of onchipmem.resource AmigaOS 4.1 component f...
I love that. In the pure Amiga tradition, it is tried to get the best of the available resources.

Max: Is it possible to put code inside ?

I agree that an higher level access could be interesting but that's maybe too early and ... overkill as you said.

A technical question. It is as fast as L2 cache but do you think the drawback is that the L1 cache is not used there ?

Do you have usecases in mind, for which it would be appropriate ?

Thanks !
Chris
Published: 2013/2/26 19:23  Updated: 2013/2/26 19:23
Amigans Defender
Joined: 11/17/2006
From: England
Comments: 3293
 Re: Release of onchipmem.resource AmigaOS 4.1 component f...
@m3x

Yes, you're probably right. In the meantime I've found a little memory pool routine which does exactly what I want (that is; allocate lots of little bits of memory that are the same size). I'm awaiting some feedback as to whether it helps performance in the wider context of the library (I'm a lowly SAM440EP owner, so can't test it myself).
SinanSam460
Published: 2013/2/26 21:24  Updated: 2013/2/26 21:24
Just popping in
Joined: 07/16/2012
From: Istanbul
Comments: 229
 Re: Release of onchipmem.resource AmigaOS 4.1 component f...
Is it possible to use this feature to speed up software like AmiCygnix or Timberwolf ?
corto
Published: 2013/2/26 21:49  Updated: 2013/2/26 21:49
Not too shy to talk
Joined: 03/30/2007
From:
Comments: 296
 Re: Release of onchipmem.resource AmigaOS 4.1 component f...
m3x: I've found a usecase in the documentation itself, that says "Use as storage area for DMA descriptors and packet data for processing by Ethernet and Security Function."

But I am sure we can find other and more original uses

SinanSam460: Maybe it is possible but the first point is to know, in this programs or others, where are the part to speedup.
Chris
Published: 2013/2/27 10:43  Updated: 2013/2/27 10:43
Amigans Defender
Joined: 11/17/2006
From: England
Comments: 3293
 Re: Release of onchipmem.resource AmigaOS 4.1 component f...
@corto

Emulators might benefit from being able to put emulated registers on-chip. Some of the older emulated machines could have their entire RAM on-chip (I was toying with the idea of trying it with my ZX81 emulator, but it likely already runs at many times actual speed already, so I'm not sure the additional speed boost would be worthwhile). I might see if I can do something with ArcEm.

I'm playing around with this but it doesn't actually benefit me
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