Re: Re: standalone code for bootstrapping

On 3/16/2019 6:33 AM, kerravon86-/[email protected] [hercules-390] wrote:
>> Actually I think the logic in sapstart should
>> be to start reading 32767 bytes from
>> head 0 record 4,
> 
> I think rereading the first block will clobber
> modified code, so it will need to instead be
> read to a different location, like 32768, just
> to get the length and the start record
> properly figured out.
The IBM code runs several steps.

After the basic 24-byte initial read it loads code from subsequent 
records, still chained to the IPL Read CCW. AFAIK, this doesn't have the 
multi-track bit set, so you still need a record 0.4 to continue the 
process. That record can then use any convention it wants for reading 
more data.

For testing it would be easier if you load from a card reader as that 
provides a faster testing environment, before you commit the changes to 
disk?


Gerhard Postpischil
Bradford, VT

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