splin@nima.berkeley.edu (Steven Lin) (04/12/91)
I've just upgraded to a Micronics 486/33 ISA. It works great, though I
have a couple of questions. Does anyone know
what switch 1-6 does? The documentation seems to say that it selects
the bus speed (between 8Mhz and 11Mhz?). Is this correct?
How about switch 1-7? What does it mean for the video-bios to be
cacheable? I don't think this switch controls relocation of the video
roms to ram because there's already an option to control that in the
the SETUP (ctrl-alt-esc) screen.
My external cache chips have the following numbers: 5C6408-15. I know
these are 15ns chips, but what size are they? 8Kx8? 32Kx8? The manufacturer's
symbol says MT. I don't recognize it.
Does anyone know where the reserved memory lies? On my old Micronics
386-16, it used to sit just below the 16Mb boundary, where QEMM could reclaim
it (QEMM calls this top memory, incidentally). Since my 486 has 16Mb, I doubt
the reserved memory is located there anymore. Where is it now? Note: I really
don't care that much if I can reclaim it. I certainly have more than enough
memory. I'm just curious about its whereabouts.
Thanks. smsmith@hpuxa.acs.ohio-state.edu (Stephen M. Smith) (04/12/91)
splin@nima.berkeley.edu (Steven Lin) writes: >I've just upgraded to a Micronics 486/33 ISA. It works great, though I >have a couple of questions.... Ah, yess.....the old mystery of the Micronics motherboard--I know it well..... > Does anyone know >what switch 1-6 does? The documentation seems to say that it selects >the bus speed (between 8Mhz and 11Mhz?). Is this correct? First I have to admit that I have the 386/33 Micronics MB. But there are some basic anomalies with Micronics' cache MB's that I believe are universal. Anyway... I have two switches for bus speed (1-3 and 1-8). But I assume your switch 1-6 does the same thing as my 1-3, so here's my guess: 1-6 OFF System speed/4 (33 MHz/4 = ~8 MHz) 1-6 ON System speed/3 (33 MHz/3 = 10 MHz) Thus for 486-25 MB's, switch 1-6 should be set ON (25MHz/4 = ~8 MHz). BTW, this is the reason (I assume) for processor speeds to be what they are--so that they can be easily divided (by whole numbers) into appropriate bus speeds (25, 33, 40MHz can each be easily divided to give 8 or 10 MHz bus speeds). Of course I could be completely wrong on that last point. > How about switch 1-7? What does it mean for the video-bios to be >cacheable? I don't think this switch controls relocation of the video >roms to ram because there's already an option to control that in the >the SETUP (ctrl-alt-esc) screen. Yes, I couldn't figure that out myself! My MB manual seems to intertwine the word "shadowing" and "caching". It calls the following memory addresses non-cacheable: 1) The 384k region between 640k and 1024k. 2) The 384k region below the 16,384k boundary. 3) The region between D00000 to DFFFFF or E00000 to EFFFFF. Here's a guess: These areas can only be addressed directly-- i.e., their contents will never be put in memory cache to be retrieved from there. My manual explains this by saying "This region is non-cacheable to enable the support of intelligent I/O cards." So you can set your video BIOS to be shadowed SEPARATELY from your system BIOS, huh? On my MB both are enabled/disabled by a single switch (1-4). So maybe your motherboard has the ability to have its video ROM put into the 15ns memory cache? Talk about FAST!!! But if your switch 1-7 shadows the video BIOS, then that's what it does--it places the BIOS of the video into high ram (640k- 1024k region; specifically, it probably puts it at C000-C7FF address. When your system does this shadowing, THEN you are able to either disable/or enable it via the keyboard. BTW, you can probably enable and disable your cache without going into setup by using CTRL-ALT-SHIFT-PLUS SIGN (numeric keypad) and CTRL-ALT-SHIFT-MINUS SIGN (numeric keypad). Check it out. (System speed is...full= CTRL-ALT-+ slow=CTRL-ALT-Minus: Note that your turbo button must be out for this to work). ...Also note that these hotkey combinations may not work correctly with QEMM installed. I found this out after two weeks of headache and many phone bills to my computer company and to Micronics Corp.!!! Another thing...if your MB manual says it shadows 128k, I'm pretty sure this is not correct. It only uses 64k for its system BIOS, and it puts it at F000-FFFF (the normal place for most computers). It's important to know this because if QEMM puts its page frame address at E000-EFFF, the "SETSYS" utility that comes with Micronics boards will scream at you (read: gives you an error message), and it will tell you to put the page frame elsewhere. If this happens, just put it after the video BIOS (FR=C800 in your QEMM386.SYS line in your config.sys file). And yet another thing...if you want QEMM to shadow your BIOS with its ROM parameter, then you can turn off the shadowing on your motherboard. The drawback about this is that you can't disable and enable the cache using SETSYS, and if you try to disable and enable the cache with the keyboard, that ALSO doesn't work with QEMM loaded...so you're back to square one: Use hardware BIOS shadowing, not QEMM's ROM parameter. Of course if you don't need to disable and enable the cache, disregard the above directions. Since my soundblaster is flaky on my 386-33 with some games while the cache is enabled, I have to be able to turn the cache on and off easily. > My external cache chips have the following numbers: 5C6408-15. I know >these are 15ns chips, but what size are they? 8Kx8? 32Kx8? The manufacturer's >symbol says MT. I don't recognize it. I don't have my machine open now, but I think mine says MT too. How many chips are there? I have 4 chips--2 in each of 2 banks. Each chip is 16k giving 64k cache. Mine are 25ns. (want to trade?) My MB manual identifies them as 8Kx8 SRAM's. (Hmmm....) > Does anyone know where the reserved memory lies? On my old Micronics >386-16, it used to sit just below the 16Mb boundary, where QEMM could reclaim >it (QEMM calls this top memory, incidentally). Since my 486 has 16Mb, I doubt >the reserved memory is located there anymore. Where is it now? Note: I really >don't care that much if I can reclaim it. I certainly have more than enough >memory. I'm just curious about its whereabouts. I think you're getting beyond me here. If it helps, my MB manual says that mine begins at segment FA000 and goes to FFFFF, and that segments FE000-FEFFF and FF000-FFFFF can be changed by my SETSYS utility to E000-EFFF and F000-FFFF. I have found that only F000-FFFF is ever used at any time by my system--I've given E000-EFFF to QEMM. (I also have to use the NRH option in QEMM to keep QEMM from grabbing part of F000-FFFF for itself which for me causes conflict.) I still haven't figured out all the mapping/remapping/shadowing stuff...even the guy at Micronics couldn't explain what my Micronics MB manual was saying!!! Well, if anybody out there has a 486-33 Micronics MB and knows anything about all this, please post because now there are two people who would like to know. Steve Smith smsmith@hpuxa.ircc.ohio-state.edu