Subject: Re: Bob's amazing hard-drive plans... In a message to Johnathan Taylor <28 Oct 94 12:44> [EMAIL PROTECTED] wrote:
>> Nope it's a disc-based z80 machine with >> builtin graphics and a flexible enough >> ram/rom banking system to allow it to >> run any portable z80 operatings system >> from the humble speccy, cpm/m2 or 3, >> probably turbodos and even unix! N.> UNIX would be unbelievably difficult N.> without any kind of MMU, I think. I never said it'd be easy;-) It'd use total swaping either to ram-disk or combined bank-swap & swap to ram-disk for the section that cannot be easily bank swapped:-) >> That's another moan I have, I hate the >> Disciple format on the sam, it was a >> bad enough idea on the disciple! drives >> would reliably read&write 84+ tracks >> but the stupid fixed allocation map >> mean't that the extra space cannot be >> used within the file-system! N.> Yeah, well look at DOS format DD disks N.> (PC) - they only hold 720k. And they N.> seem to be loads slower. Ah but CP/M aka prodos on the sam standard is only 706k but it can have 836k free space with 256 files and 32 user areas (well crude directories) and it's as fast as sam native loading and saving and random access is REAL and rapid! rather than emulated&slooow as in MasterDos! PLUS there are NO limits to the number of open files as in virtually ALL other OS's. It's even legal to open a file for read & write in two or more different places if required! I believe that on pc-clones it is possible to use 10 sectors per track and more than 80 tracks! so the maximum size of mgt-dos discs is still less than CP/M and MS-DOS practical maximums:-( >> AFAIK gzip is useless without tar to >> make sam-dos filetypes a generic serial >> file! LHARC could be used to do that >> much simpler and in less space and in one >> process! N.> Umm, I think gzip will work on any N.> file of any kind at all - to gzip it's N.> all just bits and bytes, it doesn't N.> care what it all means. Spot on:-)That's its problem! It is not capable of re-creating the original file characteristics, just the binary contents! Great for featureless bit streams like a tar archive or an opentype file but useless for CODE,DATA,SCREEN$ and BASIC filetypes with all their particular attributes that .gz files have no facility to deal with:-( While LHArc format has, easily:-) >> >> I'm begining to think that a full-blown >> >> banked unix would be MOST useful! >> >> IC> No it wouldn't. The Sam is slow >> IC> enough as it is, and besides a "proper" >> IC> Unix requires a hardware memory >> IC> management unit. Unix also requires a >> IC> large mass storage device. >> >> 1) If you're after high speed to >> compete with 66MHz DX2 then a z80 is always >> going to disapoint! >> 2) There's nothing non-unix about total >> swapping to a swap-files on a >> ram-drive. >> 3) My Sam has 4Meg external Ram fitted >> and functioning! So even without my >> IDE-HD interface and drive I'd still >> have plenty of space for unix to run in! N.> Not so sure about 4M being plenty of N.> space. It's true that Z80 programs take N.> ludicrously small amounts of memory to N.> store, but check out something like N.> Linux (a PC port of UNIX) which N.> (afaik) only really becomes usable when N.> you've got about 8M. On a clone I assume linux does quite a bit of swapping, including windowed interface that swaps video memory about to restore background windows, plus if I'm not mistaken 99% of linux apps are compiled and hence each task is inherantly large, requiring lots of memory to be able context switch at any decent speed so the tasks can be kept resident rather than using a hd based swap-file. Assuming I don't do a windowed interface... and use total swapping to the Ram-drive and don't use it for anyhting else! I'd expect each swap-file would be aprx 60k which I reckon would allow quite a few out-of context or suspended/sleeping tasks.... Swap files will never be greater than the entire task workspace which is retricted to the 16bit z80 address space less the resident portion of the kernal:-) BTW I try not to look to IBM-Clones for examples of how to do somthing right because invariably it ain't done right when its done on a clone! I prefer generic unix C for examples of how to do things, it's usually much more portable:) Cheers for the more realistic comments:-) Regards. Johnathan. ___ Olms 1.60 [Evaluation] -- |Fidonet: Johnathan Taylor 2:2501/307 |Internet: [EMAIL PROTECTED] | | Standard disclaimer: The views of this user are strictly his own.
