>Binary words in MC68000 are MSB LSB but the same on intel will >be LSB MSB >(and the Z80 is that way araoiund as well). > >Why ? >Must be a hardware thing, I always write my numbers MSB LSB myself.
The reason, as I heard it, was to save clock cycles in indexed addressing modes. If you fetch the LSB of the address/offset first, you can be adding the LSB of the index/base to it while fetching the MSB. Intel CPUs did not have indexed addressing until 8086/88 so the technique was redundant really. The 6502 had indexed addressing and 8 bit ALU so little-endian architecture did save clock cycles. I guess the designers fall into either the big-endian or little-endian camps and stay there, even when they move on and set up new companies, or new product ranges. Once you've chosen a particular architecture, compatibility across the range becomes a consideration too. Ian. >-----Original Message----- >From: Norman Dunbar [mailto:[EMAIL PROTECTED]] >Sent: 24 April 2002 11:29 >To: '[EMAIL PROTECTED]' >Subject: RE: [ql-users] QXLWIN v1.06 and partitions > > >Wolfgang, > >it's not 'stupid' it's Intel 'little Endian' format. >OK, it *is* stupid :o) > >Binary words in MC68000 are MSB LSB but the same on intel will >be LSB MSB >(and the Z80 is that way araoiund as well). > >Why ? >Must be a hardware thing, I always write my numbers MSB LSB myself. > >I'm sure Nasta will know why it is/was done this way around. > > >Cheers, >Norman. > >------------------------------------- >Norman Dunbar >Database/Unix administrator >Lynx Financial Systems Ltd. >mailto:[EMAIL PROTECTED] >Tel: 0113 289 6265 >Fax: 0113 289 3146 >URL: http://www.Lynx-FS.com >------------------------------------- > > >-----Original Message----- >From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] >Sent: Wednesday, April 24, 2002 11:22 AM >To: [EMAIL PROTECTED] >Subject: Re: [ql-users] QXLWIN v1.06 and partitions > > >On 23 Apr 2002, at 16:27, Phoebus Dokos wrote: > >> Yep it works and the interesting part is that unfortunately >he cannot test > >> it himself as his CF adapter has some problems which I hope >he'll soon >> solve either by a minor change or by a replacement (by me). >> Talk about "SuperScalar" programming... It works even if you >don't use the > >> device yourself! >Well, all the kudos here must go to .... hell, I don't know, whoever >is responsible for the Compact Flash reader behaving like a hard >drive. > >Actually, you just open a "winx_*d2d" file to the "hard disk" that is >the compact flash reader. With one exception, it then behaves like >a normal hard disk. So, to test this I just used another partition... > >The exception is that a compact disk stroes bytes within a word in >teh wrong order. Normally, the first four bytes in a QL hard disk >partition are "QLWA". Don't ask me what it means, I can undertand >the "QL" part, but the rest... > >Well, anyway, on a compact flash, this would be "LQAW". Stupid, >really. The software takes care of that. > >Oh, and whilst we're talking about partitions, there is a curious >"feature" of partitions and accessing them via a "winx_*d2d" file on >the Q60. > >Suppose you have a hard disk with 3 partitions (all 3 of them QL >partitions of course, none of that Linux stuff :-) ) > >You would probably use something like: > >win_drive 1,0,0,0 >win_drive 2,0,0,1 >win_drive 3,0,0,2 > >to access the different partitions. You would then expect a >"win3_*d2d" direct sector access file to open to the 3rd partition on >the drive - not so, IT WILL OPEN to the very first sector of the >physical disk (i.e. the partition table)- the same for win1_*d2d and >win2_*d2d. >It's not a problem, as long as you are aware of this. > >Wolfgang >This email is intended only for the use of the addressees >named above and >may be confidential or legally privileged. If you are not an >addressee you >must not read it and must not use any information contained in >it, nor copy >it, nor inform any person other than Lynx Financial Systems or the >addressees of its existence or contents. If you have received >this email >and are not a named addressee, please delete it and notify the Lynx >Financial Systems IT Department on 0113 2892990. > Visit our website at http://www.ubswarburg.com This message contains confidential information and is intended only for the individual named. If you are not the named addressee you should not disseminate, distribute or copy this e-mail. Please notify the sender immediately by e-mail if you have received this e-mail by mistake and delete this e-mail from your system. E-mail transmission cannot be guaranteed to be secure or error-free as information could be intercepted, corrupted, lost, destroyed, arrive late or incomplete, or contain viruses. The sender therefore does not accept liability for any errors or omissions in the contents of this message which arise as a result of e-mail transmission. If verification is required please request a hard-copy version. This message is provided for informational purposes and should not be construed as a solicitation or offer to buy or sell any securities or related financial instruments.
