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Thursday, November 02, 2006

Vintage Computer Mauals: S-100 RAM cards and front panel machines

John Crane

Posts: n/a
S-100 RAM cards and front panel machines
It seems most of the newer S-100 RAM cards (newer, as in 1980's) haveproblems working with front panel machines (like Altair or Imsai). Hasanyone ever published a list of what cards (Manufacturer & Model) work withfront panel machines?I've done the Imsai front panel mods to no avail, and even read ram cardmanuals that specifically mention their onboard bidirectional bus lines doNOT work with front panels, or front panel machines use "illegal states",etc. I usually get my cards on ebay and have no problem finding andreplacing fried chips, etc. Just can't (or really don't want to) battlefundamental design incompatibilities. Nowdays, ebay is filled with peopleand businesses selling vintage computer equipment that know nothing aboutwhat they sell - you know the type - lots of colorful text with paragraphson shipping/payment info and legalese but only one or two sentences aboutwhat's actually up for sale.So basically, it's been a crap shoot for me. I've got a box full of cardsthat I can't use. I really like the later cards - higher density (64K)andcooler running, but haven't found a compatible one yet. The smallercapacity cards seem to have a better chance of working - maybe because theywere earlier designs (true Altair bus vs. IEEE). Currently, my Imsai isrunning on 3 x 16K cards (Vector, Processor Tech, and Seattle) and theAltair is plodding along on 2 x 4K Mits cards.


John Crane
Today, 01:24 AM
#2
Barry Watzman

Posts: n/a
Re: S-100 RAM cards and front panel machines
I'm going to recharacterize the issue, because while you have cited thesymptom, I don't think that you understand the cause. So,recharacterizing the problem:"It seems most of the dynamic S-100 RAM cards have problems working withfront panel machines (like Altair or Imsai)."The issue isn't old vs. new, it's dynamic vs. static memory. When youuse a front panel, the computer (the CPU) is STOPPED. And as a verybroad general rule, this reeks havoc on dynamic memory cards, whichdepend on a RUNNING machine to keep their refresh going.Now there are exceptions to this, there are some (not many, but some)really good dynamic memory cards that work well in front panel machines.But they are the exception. And, in fact, I'd go further: Dynamicmemory cards from this era were a real problem, period, front panel ornot. Many of them not only didn't work with many front panels, theyoften didn't work with DMA, either. In fact, perhaps as many as half ofthem just plain didn't work reliably PERIOD. With any CPU, with orwithout a front panel, with or without DMA. The standard advice of theperiod was "stick to static memory cards". And note, the computer makergenerally regarded as having made the most reliable and stable productsof the entire period, which made over 2 dozen memory cards (I'm talkingabout Godbout/CompuPro) never made any dynamic memory cards. Theirmemory cards were all static.However, this comes back to your size issue, because static memory isfar less dense than dynamic memory. There are a number of [very good]32K static memory cards. There are a few 64K static memory cards (allusing 6116 type 2kx8 chips). And I'm not aware of any static memorycards larger than 64k.Among the relatively few good dynamic memory cards were the Cromemco16KZ (and perhaps the 64KZ), and at least some versions of the SD SalesExpando-Ram (although these can be a bitch to configure properly, withas many as 2 dozen jumper points on the board). But as a general rule,DRAM from that era was pure trouble.John Crane wrote:> It seems most of the newer S-100 RAM cards (newer, as in 1980's) have> problems working with front panel machines (like Altair or Imsai). Has> anyone ever published a list of what cards (Manufacturer & Model) work with> front panel machines?>> I've done the Imsai front panel mods to no avail, and even read ram card> manuals that specifically mention their onboard bidirectional bus lines do> NOT work with front panels, or front panel machines use "illegal states",> etc. I usually get my cards on ebay and have no problem finding and> replacing fried chips, etc. Just can't (or really don't want to) battle> fundamental design incompatibilities. Nowdays, ebay is filled with people> and businesses selling vintage computer equipment that know nothing about> what they sell - you know the type - lots of colorful text with paragraphs> on shipping/payment info and legalese but only one or two sentences about> what's actually up for sale.>> So basically, it's been a crap shoot for me. I've got a box full of cards> that I can't use. I really like the later cards - higher density (64K)and> cooler running, but haven't found a compatible one yet. The smaller> capacity cards seem to have a better chance of working - maybe because they> were earlier designs (true Altair bus vs. IEEE). Currently, my Imsai is> running on 3 x 16K cards (Vector, Processor Tech, and Seattle) and the> Altair is plodding along on 2 x 4K Mits cards.>>>


Barry Watzman
Today, 02:07 AM
#3
nospam

Posts: n/a
Re: S-100 RAM cards and front panel machines
On Wed, 1 Nov 2006 15:50:40 -0600, "John Crane" wrote:>It seems most of the newer S-100 RAM cards (newer, as in 1980's) have>problems working with front panel machines (like Altair or Imsai). Has>anyone ever published a list of what cards (Manufacturer & Model) work with>front panel machines?>>I've done the Imsai front panel mods to no avail, and even read ram card>manuals that specifically mention their onboard bidirectional bus lines do>NOT work with front panels, or front panel machines use "illegal states",>etc. I usually get my cards on ebay and have no problem finding and>replacing fried chips, etc. Just can't (or really don't want to) battle>fundamental design incompatibilities. Nowdays, ebay is filled with people>and businesses selling vintage computer equipment that know nothing about>what they sell - you know the type - lots of colorful text with paragraphs>on shipping/payment info and legalese but only one or two sentences about>what's actually up for sale.>>So basically, it's been a crap shoot for me. I've got a box full of cards>that I can't use. I really like the later cards - higher density (64K)and>cooler running, but haven't found a compatible one yet. The smaller>capacity cards seem to have a better chance of working - maybe because they>were earlier designs (true Altair bus vs. IEEE). Currently, my Imsai is>running on 3 x 16K cards (Vector, Processor Tech, and Seattle) and the>Altair is plodding along on 2 x 4K Mits cards.>>In an Altair 8800 (pre-A) chassis, the old fossil that I still haveI'd used Seals 8K static, PT 8k Static, Netronics jaws (64k dynamic)and a Vector 16k static all successfully. I see no reason why any ofthe later 64k static cards will not behave well.Now that also means I've had some horrid luck with Dynamicmemory cards. Primary reason(very few) is some relied onZ80 refresh signal. and some dislike the fact that front pannelsoften assert wait(not ready) to stop the cpu.One common altair problem is bus noise, that ringing can makeeven the best cards fail.Also if the processor clock is off timing (applies to Altair 8800A andearlier) ram timing is also smeared. Makes it hard to run well.Those earlier cards used a TTL OSC driving oneshots[eew ick]to derive timing for phase 0/1 and if either is off the cpu will stillwork but system timing can be come critical or fail.I suspect you have not looked at this machine closely enough todetermine the real problem.Allison


nospam
Today, 02:20 AM
#4
nospam

Posts: n/a
Re: S-100 RAM cards and front panel machines
On Wed, 01 Nov 2006 20:24:36 -0500, Barry Watzman< - Email Address Removed for Privacy -> wrote:>I'm going to recharacterize the issue, because while you have cited the>symptom, I don't think that you understand the cause. So,>recharacterizing the problem:>>"It seems most of the dynamic S-100 RAM cards have problems working with>front panel machines (like Altair or Imsai).">>The issue isn't old vs. new, it's dynamic vs. static memory. When you>use a front panel, the computer (the CPU) is STOPPED. And as a very>broad general rule, this reeks havoc on dynamic memory cards, which>depend on a RUNNING machine to keep their refresh going.>>Now there are exceptions to this, there are some (not many, but some)>really good dynamic memory cards that work well in front panel machines.> But they are the exception. And, in fact, I'd go further: DynamicThis was a general problem for machines of the era (altair, imsai)especially with early DRAM cards (exception was mits 88mcd or 88s4k).Later cards based on the 8202 or 8203 dram controller and some usingthe amd2964 did behave well as they were designed to look as if theywere static externally by not relying on CPU clock and key signals forrefresh and other critical timing.>memory cards from this era were a real problem, period, front panel or>not. Many of them not only didn't work with many front panels, they>often didn't work with DMA, either. In fact, perhaps as many as half of>them just plain didn't work reliably PERIOD. With any CPU, with or>without a front panel, with or without DMA. The standard advice of the>period was "stick to static memory cards". And note, the computer maker>generally regarded as having made the most reliable and stable products>of the entire period, which made over 2 dozen memory cards (I'm talking>about Godbout/CompuPro) never made any dynamic memory cards. Their>memory cards were all static.The GB/Compupro were some of the nicest static cards I have manyRam16, Ram17 (64k) and a car load of the larger Ram21, Ram22, andRam23. Ive not found a system that didn't run well with them.>However, this comes back to your size issue, because static memory is>far less dense than dynamic memory. There are a number of [very good]>32K static memory cards. There are a few 64K static memory cards (all>using 6116 type 2kx8 chips). And I'm not aware of any static memory>cards larger than 64k.Ram21 (128k), Ram22(256k) however they used 6264 8k parts.>Among the relatively few good dynamic memory cards were the Cromemco>16KZ (and perhaps the 64KZ), and at least some versions of the SD Sales>Expando-Ram (although these can be a bitch to configure properly, with>as many as 2 dozen jumper points on the board). But as a general rule,>DRAM from that era was pure trouble.All very good. DRAM of the era ranged from trash to some very gooddesigns. Most of the better ones worked very well.The gotcha with early systems especially the Altair pre B models isthe bus noise and timing jitter was terrible. On that count I'd saythe IMSAI was far better. Also many ram cards didn't like heat andthe Altair chassis was notoriously hard to cool well.Allison>John Crane wrote:>> It seems most of the newer S-100 RAM cards (newer, as in 1980's) have>> problems working with front panel machines (like Altair or Imsai). Has>> anyone ever published a list of what cards (Manufacturer & Model) work with>> front panel machines?>>>> I've done the Imsai front panel mods to no avail, and even read ram card>> manuals that specifically mention their onboard bidirectional bus lines do>> NOT work with front panels, or front panel machines use "illegal states",>> etc. I usually get my cards on ebay and have no problem finding and>> replacing fried chips, etc. Just can't (or really don't want to) battle>> fundamental design incompatibilities. Nowdays, ebay is filled with people>> and businesses selling vintage computer equipment that know nothing about>> what they sell - you know the type - lots of colorful text with paragraphs>> on shipping/payment info and legalese but only one or two sentences about>> what's actually up for sale.>>>> So basically, it's been a crap shoot for me. I've got a box full of cards>> that I can't use. I really like the later cards - higher density (64K)and>> cooler running, but haven't found a compatible one yet. The smaller>> capacity cards seem to have a better chance of working - maybe because they>> were earlier designs (true Altair bus vs. IEEE). Currently, my Imsai is>> running on 3 x 16K cards (Vector, Processor Tech, and Seattle) and the>> Altair is plodding along on 2 x 4K Mits cards.>>>>>>


nospam
Today, 07:56 AM
#5
John Crane

Posts: n/a
Re: S-100 RAM cards and front panel machines
"Barry Watzman" < - Email Address Removed for Privacy -> wrote in messagenews: - Email Address Removed for Privacy -...> I'm going to recharacterize the issue, because while you have cited the> symptom, I don't think that you understand the cause. So,> recharacterizing the problem:>> "It seems most of the dynamic S-100 RAM cards have problems working with> front panel machines (like Altair or Imsai).">> The issue isn't old vs. new, it's dynamic vs. static memory.I know about the issues with dynamic ram and I've been intentionallyavoiding those cards. A valid concern to voice though, as I neglected tomention that. In particular, I've tried Compupro Ram 16 and 17 (both 64Kstatic cards) with no success. The Ram 17 manual is the one that mentionsthe "illegal status condition" that is used by the Imsai front panel duringa write operation (p6). It does not work in an Altair 8800, or an Imsai8080. But it does work in a Sol-20. What has worked on front panels for mehas been: Econoram X cards (32K static), Vector (16K static), SeattleComputer (16K static), and Processor Tech (16K dynamic).I tend to touch the Altair only when I need to verify if something works onan Altair or not. Yes, it's a great little machine that helped change theworld, but it's SO flimsy. Everytime I touch it I'm afraid I'll break acard guide or loosen one of those infamous little wires. On the other hand,if I were to accidentally drop my Imsai, my main concern would be if I brokemy foot. As a result, I'm using the Imsai for the majority of the work. Ithas a Godbout active terminator card on the bus and a fan that I couldprobably use to build a hovercraft. It gives me a headache from all thatwind and noise with the case open. (Ever try to debug assembly with avacuum cleaner running on the desk? - Can't be done.) As a side note, I'vebeen thinking of setting up a bank of small thin 21st century fans along theleft side of the chassis. this would pull air evenly through the systemright to left.

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1 Comments:

Blogger Brandon Hudson said...

Nice post with awesome points! Can’t wait for the next one.

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