Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!think.com!spool.mu.edu!uunet!mcsun!ukc!acorn!mark From: mark@acorn.co.uk (Mark Taunton) Newsgroups: comp.sys.acorn Subject: Re: ARM3 spec changes; R260 <-> SPARC Message-ID: <7392@acorn.co.uk> Date: 3 Jun 91 10:32:33 GMT Article-I.D.: acorn.7392 References: <10615@castle.ed.ac.uk> <7333@acorn.co.uk> Distribution: comp Organization: Acorn Computers Ltd, Cambridge, UK Lines: 116 In article fl@tools.uucp (Frank Lancaster) writes: :Our R260 runs at 26Mhz. RiscIX does 16000-19500 Dhrystones depending :on screen mode. RISC OS about the same. My old A440 with 30Mhz ARM3 :did 17800 Dhrystones in Mode 0. Yes, although the R260 is faster in general (because the memory bus is clocked at 12MHz, vs 8MHz on A4xx/R140), Dhrystone all ends up in the cache so the execution time is directly related to the ARM3's fast clock rate. BTW, I get better figures on the R260 I use. Which Dhrystone (1 or 2) is being used? :A few points concerning the R260 as a UNIX workstation: : : 1. I don't like preinstalled UNIX systems on hard disc with NO backup : supplied. What are you supposed to do if you accidently remove the : kernel!? The problem with any other distribution scheme is that it costs more (=> increased system price) and besides, there are several different media & formats which people might want to use - we can't support them all. It is just not sensible to try to run a UNIX box without *some* form of backup (even if it is just a large box of floppies) so I really don't see the problem. You are certainly expected to back the system up: it's clearly explained in the System Administrator's Guide. Even so, in the case of the unlikely event you speak of, your supplier and/or the support service should be able to assist - it's what they're there for. : .. I didn't find : out if you could specify a floppy disc as swap space You can't: there really isn't enough space on a floppy for the purpose. Besides, what do you do if the system wants to write to the swap floppy when you have the file system floppy in the drive? Yes, doing a RISC OS style floppy disc naming scheme is *possible* but it doesn't make economic sense for us to put such effort in given the rarity with which such a thing is needed. : 2. Next I wanted to reconfigure the hard disc with a larger RISC OS section, : as we develope both UNIX and RISC OS software. Hmm, a programme is supplied : to do this, but of course it destroys all data on your hard disc! So you : either need a second hard disc (we didn't have a spare one) or you have : to boot discless without hard disc. Sorry, that's just a fact of life: if you increase the size of the RISC OS section you will need to reduce the size of the main RISC iX file system partition. That cannot be done on an existing file system (and certainly not with the file system mounted), so you need to back up, do the modification with running from a different root device, then reload. : 3. Booting without hard disc via ethernet. Well, this wasn't easy. : The R260 isn't supplied with all software required for a discless boot. Indeed. The standard distribution is designed for discfull use, since the R260 comes with a hard disc. We also sell the R225 discless workstation, for networked operation, and suitable software is supplied with that. Crude analogy: if I want an open top car, I don't expect the manufacturer to supply me with tools and detailed instructions on removing the lid of my saloon :-) : [ explains how discless booting can be done ] : ... It worked! Congratulations! For people who really do want to run discless, it is probably better to buy an R225 and upgrade it if required. : 4. Next I wanted to reconfigure the kernel. On SUN systems you can relink : the kernel after changing and compiling the parameter files, so you : can remove unused device drivers etc. On the R260, as supplied, you can't : relink the kernel. Well, we love adb (the standard UNIX debugger) and : started patching the kernel (more file buffers, yummy!) With the RISC iX 1.2 kernel there is little need to remove unused device drivers: the system automatically reuses most of the memory they take up. I strongly advise against attempting reconfiguration patches without documentation: do you *really* know what you are doing? In any case, a Kernel Binary Kit is available: it provides all that is needed to reconfigure the kernel for specific requirements, *and* explains the limitations on parameters - contact your supplier. : 5. On RISC OS I use a module to improve the screen modes on my multisync : monitor (less flicker, larger picture). Alas, reconfiguring the screen : modes is again undocumented. But debugging the kernel is fun, and we : discovered a variable called video_mode which points to the VIDC paramter : table for the current screen mode. The rest is easy, calculate the : parameters for the VIDC, patch the VIDC tables, and reboot! AAAAAaaaaaarrrrrgggggggghhhhhh!!!!!!!! Debugging the kernel may be fun, but we really can't support you if you pull stunts like that! Reconfiguring the screen modes is undocumented because it's not something we intend anyone to do. What if your patch goes wrong (or you don't fully understand what you are modifying), and the kernel then malfunctions in such a way as to corrupt your filesystem? :After all this criticism, you may think that I hate this machine. But no, I :actually quite like it. Its the fastest Archimedes around with the best :operating system on it. Only it could be a lot better... :Switching between RISCIX and RISC OS doesn't take long, booting UNIX :without disc checks takes about 1min. GNU emacs is supplied, but not the :newest version. Networking with SUNs works without any problem, overall :performance of UNIX is quite okay, not much swapping and disc access is fast. Thank you for your comments. Glad you like it. I hope this wasn't too boring for the many readers not using RISC iX.... -- Mark Taunton Email: mark@acorn.co.uk Acorn Computers Ltd Phone: (+44) 223 214411 Cambridge, UK Fax: (+44) 223 214382