[Coco] Coco Digest, Vol 164, Issue 42

[L. Curtis Boyle]

Yes, it was done purely for performance reasons (the header check is still done, as far as I know). There was a command “CRC” (with options “ON” or “OFF”) where you could dynamically turn it on or off while running, without needing to reboot or modify the boot file… not sure if that is still part of the current default NitrOS-9 distribution these days.

L. Curtis Boyle
curtisboyle at sasktel.net

TRS-80 Color Computer Games website
http://www.lcurtisboyle.com/nitros9/coco_game_list.html



> On Jun 17, 2016, at 8:35 AM, Barry Nelson <barry.nelson at amobiledevice.com> wrote:
> 
> Which byte needs to be patched to what to enable CRC checking?
> 
>> Tormod Volden lists.tormod at gmail.com 
>> Fri Jun 17 10:16:29 EDT 2016
>> 
>> On Fri, Jun 17, 2016 at 4:10 PM, Bill Pierce via Coco wrote:
>>> Ok, changed a byte in the "dir" command, and it loads and fails miserably LMAO
>>> I tried both typing the command directly and manually loading it. NitrOS9 allowed the module to load, though it failed when run. In fact, not only did hang up VCC, but DW4 as well... I had to restart both.
>>> So no CRC checking is done at all. I may heve been remembering seeing CRC errors from the old days before Nitros9 LOL
>>> 
>>> My questions would be, is this a good thing or bad? A lot of crashes could be avoided with CRC checking was "On". Why was it turned off? Was it off in the original OS9?
>>> I know "boot", "REL" and "Krn" have modified headers (mainly for the "dos" loading and relocation code) and will not check properly until they are "in place" after booting. Maybe this is why it was turned of (??). I would think since these modules are loaded and executed before anything else that crc checks on them (after the boot) would be redundant.
>>> 
>> 
>>> From the code comments, and Brett's observations, I think it is purely
>> for performance reasons. You can enable it by patching init, and I
>> think all system modules will still load fine, just slower.
>> 
>> Tormod
> 
> 
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