Tony Duell wrote: TI realized early on that to make the DSP more ubiquitous, they needed to suppport masked parts. Particularly for this sort of application. I would suspect this is a low end 32010-ish part (?) Ah, OK. I would assume the controller would exploit page mode references (especially when dealing with sequential accesses like video). If so, this muddies any attempt to convert multiplexed addresses back to a form suitable for SRAM (unless you use SRAMs that also support page mode access!) Yes, assuming it produces an 18bit (9R+9C) address, 41256's would be the right way to go.

I am not sure, and the service manual (which I have) doesn't make any obvious reference to this. It does... There are 2 standard memory configurations for the CoCo3. The first is a 128K system using 4 off 41464 (64K*4) chips on the mainboard. The second is a 512K system using a duaghterboard that takes 16 off 41256s. Note that 256K*4 parts can't easily be used, since IIRC they have 10 address lines and need a 10-8 split of the 18 address bits. I am really thinking back now, but there are a couple of RC networks on the CoCo3 board that fiddle the RAS and CAS timing. I seem to remember you remvoe at least one of the capacitors when you go from 128K to 512K (as well as pulling the 4 soccketed DRAMs from the mainboard [1] and fitting the daughterboard). I did this many years ago, when the CoCo3 was still in production. [1] And those 64K*4 chips are just what you need to bring CoCo2's from 16K to 64K. IIRC, that's where the ones from my CoCo3 ended up. -tony

[CoCo 3 GIME] Sure. But I think the only timing diagram is a 'representative' one showing a normal cycle. No idea if it does other types of cycle as well. -tony

Rumor has it that Tony Duell may have mentioned these words: Yup. Nope. But the *boards* to stick 'em in aren't exactly easy to find, and Cloud 9 (http://www.cloud9tech.com/) aren't building/shipping any more hardware (including their 512K upgrade boards) until they get the SuperBoard done; which might be quite a while yet. Besides - I have bigger fish to fry. This is part of my evil, twisted plot for world domination!!! OK, just kidding, but - to venture into where my brain & dynamic memory part understanding, the 41256 uses a particular refresh[1] which newer memory doesn't deal with well[2], so going *beyond* 512K is problematic.[3] *If* I can figure out how to get 512K of SRAM to work in a CoCo3, going *beyond* 512K might become a bit easier. Not to mention - going from SRAM to FRAM would be a pretty easy jump. A CoCo3 with a "Suspend" switch could be *neat*. ;-) Or, I might be full of condensed milk, as my father-in-law used to say. Just my random thoughts for the day... Laterz, Roger "Merch" Merchberger [1] 256 cycle / 8-bit counter / something like that. Did I mention that my brain doesn't grok DRAM well??? ;-) [2] 512/1024 cycle / 9-10 bit counter / something like that. Just in case you didn't catch it, I have DRAMophobia. ;-) [3] Now we're getting into the world of PAL/GAL/PEEL/CPLD - which is *way* beyond anything comprehensible to my grey matter. -- Roger "Merch" Merchberger | "Bugs of a feather flock together." sysadmin, Iceberg Computers | Russell Nelson zmerch at 30below.com |

Rumor has it that woodelf may have mentioned these words: Browser schnauzer... "We no need no steeekin browser!" With OS-9, one can have Rogue (think old Nethack) playing in one window (and I redesigned the screen fonts so the "guy" looks like a guy, and scrolls are scrolls, etc. instead of remembering the symbols -that alone cannot be done in 128K), DynaCalc running in another window, Basic09 in a third (and who wants to run Basic09 in 8K??? Heck, give 'er 40K! Why? 'Cause you can!) and a 150K RAMDisk. But what if you needed a 300K RAMDisk? Now you need more than 512K RAM. ;-) 2 questions: 1) Is there such a thing as "fake 12-bit bytes?" ;-) 2) What would I want that for? Some people *like* 8-bit bytes (me included) - I just want more than 512K of RAM in my CoCo. The patches to OS-9 already exist to give it access to 2M, one just needs to shoehorn functional memory into the critter to do it. That, and to learn more about memory; altho the more I learn about DRAM, the more I *like* SRAM. ;-) Laterz, Roger "Merch" Merchberger -- Roger "Merch" Merchberger | "Profile, don't speculate." SysAdmin, Iceberg Computers | Daniel J. Bernstein zmerch at 30below.com |

Err, it's just traces to link the DRAMs to the connectors. And isn't the track layout in the service manual (you do have the service manual, right?). In which case it would be a lot easier to make your own daughterboard than to mess around trying to kludge SRAMs onto the GIME. There were a lot of myths about how critical the layout was with DRAM (and Rainbow printed some of them). Yes, you do need to take care. It is a high-speed circuit, you should try to keep traces the same length, decoupling is _essential_ as is a low-impedance ground track. But to be honest, making an SRAM board that runs at the same speed is no easier. -tony

Dave McGuire wrote: You need to stagger refresh in big arrays. Just like gating RAS/CAS to only those banks that *need* to see them for *this* particular cycle -- for exactly this reason. The problem is present even on small arrays. <grin> I worked on a "600 pin tester" (i.e. be able to stimulate and monitor the states of 600 different signals on the unit-under-test) in the late 70's. The "stimulus memory" was two "doors" (large -- ~18" x ~60" -- wirewrapped panels on hinges fed with *thick* copper bars for power distribution) full of bipolar & ECL memory devices. I.e. *hundreds* of amperes. Due to the mix and match of logic families (CMOS/TTL/ECL), you had lots of odd supply voltages on the boards (-5.2, -1.2, +5, +12, etc.) -- in addition to the other supplies for the "pin drivers" (the UUT is driven with signal levels that are programmed from a variable range of output voltages). Needless to say, *lots* of decoupling capacitors *everywhere*. When the boards came in from the wirewrap house, there was a short between two of the supplies (or, perhaps, a supply and ground). Trying to figure out *where* the short could be in a panel of that size COVERED with teflon wires was HUGELY intimidating! Long story short: the bypass caps were the wrong voltage. So, as soon as power was applied, the HUGE power supplies would very happily fry each cap to a dead short. Happy ending: wire wrap vendor had installed the caps so wire wrap vendor had to do the rework! ;-)

Dave McGuire wrote: Yeah. Before starting work each day, you would remove your wristwatch, wedding ring, belt buckle, etc. Sure, everything was "low voltage" (I think the pin drivers max'ed out at 64V -- or maybe 32? The power supplies were digitally programmable so it was some nice binary number...). So, you weren't worried about getting electrocuted but, rather, *cooked*! One of my buddy's could never get his wedding band off so he would have to wrap it in a bandaid. Of course, bandaids are (back then) pseudo-flesh-colored so the standing joke was that he was having an affair and needed to keep his wedding band/marital status out of view! ;-) And it's all (deliberately) point to point so it's truly tangled. I still am unconvinced that the beast could actually *work* given that *apparently* random fabrication technique (the array was clocked at 100MHz -- no, it must have been 125MHz because the cycle time was 8ns). Perhaps the designers had carefully considered *placement* of the components and thus indirectly influenced signal lengths, etc. <shrug> TIP: An embroidery hook works wonders for fishing wirewrap wires out of a nest without too much damage! ;-) (but you have to find the right size hook to ensure a "good grab" on the wire)

On Aug 18, 2006, at 4:54 PM, Tony Duell wrote: Well let's put it this way. I was the sixteen-year-old kid coming in to wire-wrap and test after school, and the two Princeton University professors were the ones doing the design. Many people suggested heavier bypassing, but were smacked down at every turn, and "everybody knows the PhDs know better!" *spit* -Dave -- Dave McGuire Cape Coral, FL

On Aug 19, 2006, at 6:55 PM, Tony Duell wrote: My sentiments exactly. Since then, I've cleaned up the impractical, impossible messes of several of 'em. -Dave -- Dave McGuire Cape Coral, FL

On Aug 20, 2006, at 6:38 PM, Tony Duell wrote: You signed it "De ARD", correct? I assumed it was a ham radio reference. -Dave -- Dave McGuire Cape Coral, FL

On Aug 20, 2006, at 7:25 PM, Tony Duell wrote: OH oh oh oh. I thought it was "De". Well since YOU'RE the one I send electronics questions to when I can't figure something out, I think you know that I respect your knowledge. :-) I had no idea you're into particle physics. That is extremely cool. -Dave -- Dave McGuire Cape Coral, FL

On Monday 21 August 2006 05:50 pm, Tony Duell wrote: Why is that? I've no real experience with "unix" per se, though I do run linux here on multiple boxes, and I don't know a darn thing about VMS (yet). Though it did come up in some offlist correspondence recently. -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, a critter that can be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin

On Tuesday 22 August 2006 05:52 pm, Tony Duell wrote: Actually that explains it pretty well, as there are any number of software packages, both operating systems and applications, where I've felt like I was fighting it more of the time than not -- which sounds like what you're describing here. And I'd really rather not. I have better things to do with my time. In what sorts of things might it be considered superior? -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, a critter that can be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin

Well, it's been a while since I played with VMS, but.... VMS is generally far better at keeping independent users from interfering with one another through exhaustion of common resources. The VMS privilege model is immensely better than the Unix one (much finer-grained). VMS has better support for structured files of various sorts, and, while I've never measured it, I suspect VMS's performance is better when dealing with very large directories (tens or hundreds of thousands of entries in a single directory). There are various epiphenomenal differences as well (such as the support for various languages), but those are really differences in the support infrastructure rather than differences in the OSes proper. /~\ The ASCII der Mouse \ / Ribbon Campaign X Against HTML mouse at rodents.montreal.qc.ca / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B

On Sun, 20 Aug 2006, der Mouse wrote: Ah, but the real point is that PhD's don't make misteaks, certainly not spelling ones. -- Grumpy Ol' Fred (UC Berkeley aluminum)

On Mon, 21 Aug 2006, Sridhar Ayengar wrote: How rigid, or how skilled we are, with spellinq may be related to what schools we are aluminiums of. -- Grumpy Ol' Fred