Wanted: ICD RAMBO XL Schematic

[Dopeyman06]

1 hour ago, TZJB said:

From what I can gather without the datasheet, the MK4128 is 2x 4164 in one chip.

 

26 minutes ago, ClausB said:

Or perhaps the 4128 is a 41256 with bad bits on one half, so only 128Kb are useful. This was common practice in early days of new DRAM chips, when yields were low.

Thank you for the comments. I've sent payment to the person selling the chips. So in total I'm getting 22 of the 256k DRAMs. Not the 6 Mostek chips.

[TZJB]

10 hours ago, Dopeyman06 said:

 

Thank you for the comments. I've sent payment to the person selling the chips. So in total I'm getting 22 of the 256k DRAMs. Not the 6 Mostek chips.

 

There are 22 physical 256Kb DRAM chips of unknown status as it appears the seller hasn't tested them. Either way the MK4128 are unusable for your application even if they work. They may be usable as 64Kb 4164 but that's not the requirement.

 

10 hours ago, ClausB said:

Or perhaps the 4128 is a 41256 with bad bits on one half, so only 128Kb are useful. This was common practice in early days of new DRAM chips, when yields were low.

 

I did read that theory too. It seems strange that there is no datasheet commonly available. Maybe it's because both theories are true which could cause confusion.

 

There are plenty of MK4128 available on eBay! Here is a piggy-back one that purports to be a 4464 supporting my original theory. https://www.ebay.com/itm/394263083350?

Edited June 8, 2023 by TZJB

[ClausB]

1 hour ago, TZJB said:

Here is a piggy-back one that purports to be a 4464 supporting my original theory.

Unlikely. 4464 has 18 pins with 4 data pins, not at all pin-compatible with 4164 nor 41256.

 

Some discussion on VCF:

https://forum.vcfed.org/index.php?threads/mk4128-dram.1239270/

So my guess was wrong.

Edited June 8, 2023 by ClausB

[TZJB]

2 hours ago, ClausB said:

Unlikely. 4464 has 18 pins with 4 data pins, not at all pin-compatible with 4164 nor 41256.

 

Some discussion on VCF:

https://forum.vcfed.org/index.php?threads/mk4128-dram.1239270/

So my guess was wrong.

 

I agree that a normal 4464 would use 18 pins, but if a 4128 has 2x 64Kb then piggybacked they would have 4x 64Kb. Reading that forum it would suggest that a 4128 used separate RAS inputs but common CAS. I assume that the Data inputs/outputs would be separated too at pins 2 & 14 with pin 1 as RAS1 at a guess.

[ClausB]

Look at the datasheet linked in that forum:

https://www.minuszerodegrees.net/memory/41128/datasheet_KM4128.pdf

 

[TZJB]

1 minute ago, ClausB said:

Look at the datasheet linked in that forum:

https://www.minuszerodegrees.net/memory/41128/datasheet_KM4128.pdf

 

 

Thanks @ClausB you found the datasheet. It's certainly not how I imagined it...Stacking chips? Who would ever do such a thing? 😉

[_The Doctor__]

512k and up peterson upgrade physically stacked chips as did USD for floppy, manufacture of internally stacked chips why not!

[TZJB]

1 hour ago, _The Doctor__ said:

512k and up peterson upgrade physically stacked chips as did USD for floppy, manufacture of internally stacked chips why not!

 

I was joking as ironically I have done all of those and more. I wasn't aware an IC manufacturer would need to though.

[Dopeyman06]

Another question regarding the resistor and the capacitor.

 

Is there a specific way to solder these items? Meaning, is there a negative and positive? Or can can the be soldered in any orientation?

 

[TZJB]

9 minutes ago, Dopeyman06 said:

Another question regarding the resistor and the capacitor.

 

Is there a specific way to solder these items? Meaning, is there a negative and positive? Or can can the be soldered in any orientation?

 

 

Both the resistor and capacitor are non-polarised and can be fitted either way in this instance.

[_The Doctor__]

@Dopeyman06

while the components in this instance don't care, best practices are to face marking and bands to match orientation of all the others on a PCB. Make a mechanical as well as soldered contact clipping excess leads within the circumference or perimeter of the pads the component leads occupy.

Edited June 17, 2023 by _The Doctor__

[Dopeyman06]

8 minutes ago, TZJB said:

 

Both the resistor and capacitor are non-polarised and can be fitted either way in this instance.

Awesome! Thanks!

 

[Dopeyman06]

On 5/14/2022 at 4:34 PM, mytek said:

Today I did something I had been resistant to do, and that was stripping all the components from my one and only original ICD RAMBO XL PCB so that I could really see all the trace connections more clearly. ICD used very tiny pads, so I did have a couple lift unfortunately, Well I guess it's a good thing I'm designing a replacement  

 

  

 

After doing this I could see that all unused inputs were indeed not left floating, and instead are pulled high (+5V). I also saw two places for decoupling capacitors to go (I marked these with yellow rectangles), However my board never had these installed.

 

The cap down by where the RAMBO would plug into either U7 or U27 was redundant considering that the chip socket on the Atari motherboard already has its own decoupling cap, however the one shown between IC4 and IC5 is a good precaution.

 

So I updated my schematic as well as the clone PCB to pull-up the unused inputs and to include one decoupling capacitor. We are now at Version 1.1 for the board with these changes. So I guess now it would be permissible to substitute SN74HCTxxx parts for the 74LSxxx ones, since all inputs now go somewhere (I should have done this right from the get go).

 

Updated schematic: RAMBO_XL-II_V1.1_schema.pdf

 

 

I'm now ready to order a few sample boards ?

 

Hello. I've created the RamboXL clone of yours and successfully installed one into my 800xl. Thank you. 

 

Just one question regarding your original ICD Rambo XL. In the manual (page 8 ) it talks about shrink tubing and a ribbon cable. Do you still have that ribbon cable? If so, can you post a pic or two of it? It's just a curiosity thing. And possibly satisfy my OCD.  LOL!

[+mytek]

3 hours ago, Dopeyman06 said:

Hello. I've created the RamboXL clone of yours and successfully installed one into my 800xl. Thank you. 

 

Just one question regarding your original ICD Rambo XL. In the manual (page 8 ) it talks about shrink tubing and a ribbon cable. Do you still have that ribbon cable? If so, can you post a pic or two of it? It's just a curiosity thing. And possibly satisfy my OCD.  LOL!

They were describing connecting the ribbon cable that ICD permanently attached to their Rambo XL board and connecting that to the PIA pins, using small pieces of heat shrink slipped over the pins and the soldered connection. I kinda went a different route when I cloned their board, by adding a 9 pin header (J4) and combining both the original A,B,C,D motherboard connections as well as the five PIA connections. Thus the idea is to purchase a cable similar to below in order to mate with the 9 pin header on the clone Rambo XL.

 

Here's just one of many possibilities, with the length dictated by the actual situation.

 

eBay LINK

 

[Beeblebrox]

Many Atarians's tinkering with upgrades use those excellent Dupont connectors. So much better to match the header array with the same number dupont connector, as they also stay connected far better than using individual/single ones. (Essential for many upgrades (like U1MB/VBXE/UGV, etc) to have solid connections). Also using Dupont connectors means you can take A8s apart so much easier). (I know I am stating the obvious here).

 

In the UK I buy these Dupont kits which are very cheap and great for the headers Mytek mentions:

 

https://www.amazon.co.uk/gp/product/B0774HCRY1/ref=ppx_yo_dt_b_search_asin_image?ie=UTF8&psc=1

 

Dupont Connector Kit 2.54mm Crimp Pin JST SM Connectors 1 2 3 4 5 6 Pin Crimp Housing Connector with Dupont Wire and Male Female Crimp Pins...

 

 

[+mytek]

Thank you @Beeblebrox for adding a source for that Dupont connector kit 👍

 

6 minutes ago, Beeblebrox said:

So much better to match the header array with the same number dupont connector, as they also stay connected far better than using individual/single ones.

Just so @Dopeyman06 and others are made aware, the eBay link I provided in my previous post was for a complete cable assembly already having a common 9-pin female housing (not individual ones), thus making for a single insertion into the Rambo XL clone board's J4 pin header. Also no wire stripping or terminal crimping required on the Rambo side of things   That link is for a double-ended cable, so if the length works out, you might get two cables from the one being purchased.

[Beeblebrox]

1 minute ago, mytek said:

Thank you @Beeblebrox for adding a source for that Dupont connector kit 👍

 

Just so @Dopeyman06 and others are made aware, the eBay link I provided in my previous post was for a complete cable assembly already having a common 9-pin female housing (not individual ones), thus making for a single insertion into the Rambo XL clone board's J4 pin header. Also no wire stripping or terminal crimping required on the Rambo side of things   That link is for a double-ended cable, so if the length works out, you might get two cables from the one being purchased.

@mytek  thanks for clarifying, good to know.

[+mytek]

Just now, Beeblebrox said:

@mytek  thanks for clarifying, good to know.

Yeah I have one of the kits you linked to just for those situations requiring a quick custom cable that I don't presently have on hand. But normally I prefer to get the cables already made to spec and pre-crimped, because making your own is pretty fiddly. That link I provided lets you select anything from 1-10 positions, and a cable length from 10-50 CM.

[Beeblebrox]

1 hour ago, mytek said:

Yeah I have one of the kits you linked to just for those situations requiring a quick custom cable that I don't presently have on hand. But normally I prefer to get the cables already made to spec and pre-crimped, because making your own is pretty fiddly. That link I provided lets you select anything from 1-10 positions, and a cable length from 10-50 CM.

Know what you mean.

Oddly (and this is probably just me), I find making up/crimping my own Dupont cables strangley relaxing heh heh! I've made quite a few for the likes of U1MB, Incognito, VBXE, UGV, TK-II over the last few years.

 

The main reason I like making my own is I often have very deliberate cable colouring schemes which I stick to. I have one of those brains where if I have a ribbon cable all the one colour (eg grey), I can so easily get into a muddle as to wiring up during an upgrade. My own colour schemes have helped no end to un-befuddle me heh heh! Especially for upgrades such as VBXE (with Din13 RGB) and Incognito. I have a big roll of multicoloured ribbon cable.

 

I'll have a look around for a UK supplier for the premade ones just in case I ever change my mind.

 

BTW installed another of your excellents UGV's in another recently fixed 65XE of mine a couple of days ago. (Said XE had a bad O/S Rom chip which I finally found was the culprit). As ever the video output from the horrible stock XE video is so much better with UGV, even more so when on S-video. I plan to install U1MB and another TK-II in it so whilst in there I added the respective required sockets. 

 

Anyways, going off on a tangent. Dupont rules!!!

 

Edited June 26, 2023 by Beeblebrox

[Dopeyman06]

4 hours ago, mytek said:

They were describing connecting the ribbon cable that ICD permanently attached to their Rambo XL board and connecting that to the PIA pins, using small pieces of heat shrink slipped over the pins and the soldered connection. I kinda went a different route when I cloned their board, by adding a 9 pin header (J4) and combining both the original A,B,C,D motherboard connections as well as the five PIA connections. Thus the idea is to purchase a cable similar to below in order to mate with the 9 pin header on the clone Rambo XL.

 

Here's just one of many possibilities, with the length dictated by the actual situation.

 

eBay LINK

 

That's similar to the cable that I purchased for your board. But I was actually asking about the original cable that came with the ICD RamboXL. I was just curious on how it looked.

[+mytek]

10 minutes ago, Dopeyman06 said:

That's similar to the cable that I purchased for your board. But I was actually asking about the original cable that came with the ICD RamboXL. I was just curious on how it looked.

The original board I had didn't come with it if I recall correctly, so I really don't know what it looked like. Perhaps somewhere in this thread or with a Google search you could find a picture.

[ClausB]

As for the PIA end of the cable, I recommend not soldering to the chip. Pull the PIA from its socket, bend those 5 pins straight out, and plug it back in. Cut a 5-pin section from an IC socket and solder the cable to that. Then slide the socket section onto the 5 exposed pins. That's how I did the original.