Shift838 Posted March 24, 2020 Share Posted March 24, 2020 I've been cross referencing chips for the IDE card. Of course the 512k SRAM is no longer available. I believe I have a found a suitable replacement but I would like a couple of sets of extra eyeballs to look at it to make sure I am correct. The M68Z512W.pdf is the datasheet for the original. I found IS62WWV5128BLL , CY62148GN and CY62148EV30LL These 3 appear to be the same to me, but the last (CY62148EV30LL) may be a bit light on the voltage side. M68Z512W.pdf IS62WWV5128BLL.pdf CY62148GN.pdf CY62148EV30LL.pdf 1 Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/ Share on other sites More sharing options...
brain Posted March 24, 2020 Share Posted March 24, 2020 (edited) deleted, since the forum won't let me check "notify on replies" if I forgot the first time. Edited March 24, 2020 by brain forum issue 1 Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4489751 Share on other sites More sharing options...
brain Posted March 24, 2020 Share Posted March 24, 2020 They all look like good options to me (I assume the IDE card has a 3V3 rail for this IC. If so, the last items should be fine. Jim 1 Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4489753 Share on other sites More sharing options...
matthew180 Posted March 24, 2020 Share Posted March 24, 2020 The ISSI part comes in two TSOP-32 pinouts, you need the Type-2 pinout, which is designated by the full part number (shown below). The CY62148GN comes in a 5V and 3.3V version (again, full part numbers specify the voltage and package), and the 3.3V version is not available. The original part is 3.3V, so I'll assume you need 3.3V. So the CY62148GN is not an option. The CY62148EV30LL is available but costs more. Also, the Cypress parts are 45ns, so you are paying for speed you don't need. The ISSI part is 70ns and cheaper. Octopart is your friend! Also, the original part is available from four vendors, but you will have to make an offer and probably buy the complete stock. But three of the four have between 30 and 80 pieces, so if that is enough for your build, you can probably get them for a pretty good price. Offer $2/piece and see what they say. https://octopart.com/search?q=M68Z512W¤cy=USD&specs=0 Original: Full Part Number Package Vcc Speed Availability M68Z512W-70NC1 , TSOP-32, 3.3V, 70ns, Make offer for complete stock Replacements: Full Part Number Package Vcc Speed Cost DigiKey Mouser IS62WV5128BLL-55T2LI, TSOP-32 type2, 3.3V, 70ns, $3.84, 622, 1067 CY62148GN-45ZSXI , TSOP-32, 5.0V, 45ns, $4.92, 220, 222 CY62148GN30-45ZSXI , TSOP-32, 3.3V, 45ns, not available CY62148EV30LL-45ZSXI, TSOP-32, 3.3V, 45ns, $4.51, 1771, 268 When you have an equal choice, let availability and cost be your deciding factors. My rules for using a part: 1. Must be in active status with the manufacturer. 2. Must be available from both DigiKey and Mouser. 3. Must be regularly stocked. 4. Must have decent documentation / datasheet. But in this case, I would probably make offers to the three vendors who have new-old-stock, since this is a limited buy for a specific purpose. 2 Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4489911 Share on other sites More sharing options...
GDMike Posted March 25, 2020 Share Posted March 25, 2020 I guess this requires a clock and adding a battery for "keep alive" won't work? Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4490193 Share on other sites More sharing options...
Shift838 Posted March 25, 2020 Author Share Posted March 25, 2020 8 hours ago, matthew180 said: Original: Full Part Number Package Vcc Speed Availability M68Z512W-70NC1 , TSOP-32, 3.3V, 70ns, Make offer for complete stock Replacements: Full Part Number Package Vcc Speed Cost DigiKey Mouser IS62WV5128BLL-55T2LI, TSOP-32 type2, 3.3V, 70ns, $3.84, 622, 1067 CY62148GN-45ZSXI , TSOP-32, 5.0V, 45ns, $4.92, 220, 222 CY62148GN30-45ZSXI , TSOP-32, 3.3V, 45ns, not available CY62148EV30LL-45ZSXI, TSOP-32, 3.3V, 45ns, $4.51, 1771, 268 Thanks Matt! I have been using octopart. I found it a few weeks ago when I was staring to learn Fusion 360 while I was looking for 3d models of components. I have already made offers to the various vendors that show stock on octopart and have not heard back yet. That's why I was looking for a suitable replacement. So what I am interpreting from your post is that the one that will work although it's a bit faster is IS62WV5128BLL-55T2LI Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4490242 Share on other sites More sharing options...
matthew180 Posted March 25, 2020 Share Posted March 25, 2020 14 hours ago, Shift838 said: when I was staring to learn Fusion 360 while I was looking for 3d models of components. Personally I try to avoid the commercial software with hobby projects, even if there are "free" versions (there is always a catch). My preferred tools for PCB work are KiCAD and FreeCAD. I know the FreeCAD learning curve is a brick-wall, but it is actually not too far from SolidWorks in workflow and capability, and worth learning IMO. Check out Joko Engineering on YouTube, example: There is also a plug-in to FreeCAD for importing KiCAD boards, and to help get STEP files aligned with KiCAD footprints. Importing the PCB lets you do things like validate the mechanical fit, assuming you have your enclosure modeled in FreeCAD. KiCAD itself is awesome these days (and getting better all the time) and provides a lot of parts with 3D models in the stock library. For missing parts it is pretty easy to make your own. If you are missing 3D STEP models, check the manufacturer's website first, a lot of them provide models for their parts. If you can find a STEP file online, then you can import it with FreeCAD and get the part aligned to the footprint and exported to STEP and WRL (KiCAD uses both formats for rendering). I make all my own footprints, or verify any existing ones against the datasheets; I don't need any surprises when I get my boards back from OSHpark. There is a big difference between just making a PCB, and making a PCB that can actually be manufactured. You have to pay attention to *all* the details, and make sure you know the capabilities of the PCB shop you are using. 13 hours ago, Shift838 said: So what I am interpreting from your post is that the one that will work although it's a bit faster is ... Ah, there was an error in my table. The ISSI "*ALL" part is 70ns at 2.5V. The ISSI "*BLL" part is the 3.3V version with a 55ns access time. When it comes to memory, "speed" refers to access time, so the smaller the number the faster the memory; and you pay more for faster access. The original part is 70ns, the 3.3V ISSI part is 55ns (so slightly faster), and the Cypress parts are 45ns (faster than both original and ISSI). Typically, all other characteristics being equal, faster memories can be used to replace slower memories. Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4490617 Share on other sites More sharing options...
F.G. Kaal Posted March 26, 2020 Share Posted March 26, 2020 On 3/24/2020 at 4:07 PM, brain said: They all look like good options to me (I assume the IDE card has a 3V3 rail for this IC. If so, the last items should be fine. Jim There is no 3.3 volts available on the original IDE card design!!! 1 Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4491576 Share on other sites More sharing options...
matthew180 Posted March 27, 2020 Share Posted March 27, 2020 Then you will have a problem, even with the original SRAM. The absolute maximum Vcc is 4.6V, and you do not want to operate at or near that range. None of the SRAMs have 5V tolerant I/O either. I just assumed that since the original part was 3.3V that there was compensation (at least a 3.3V reg) built into the design. If it works, which it probably will for a little while, it will not be stable and reliable long term, IMO. Best to find a 5V SRAM. Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4491885 Share on other sites More sharing options...
brain Posted March 27, 2020 Share Posted March 27, 2020 5 hours ago, F.G. Kaal said: There is no 3.3 volts available on the original IDE card design!!! Then the information in the original post must be incorrect. In the original post, the original part was described as M68Z512W and the datasheet for that part was attached. The PDF shows the voltage span for that device as 3V3 (2.7 to 3.3 or so...) So, if that is the part on the original design, something must have supplied it with 3v3. Jim Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4491951 Share on other sites More sharing options...
matthew180 Posted March 27, 2020 Share Posted March 27, 2020 I assume the design is coming from the TI Tech Pages? http://www.nouspikel.com/ti99/titechpages.htm A quick check and I don't see any specific SRAM called out, only the clock IC, and the strange combined clock+SRAM ICs: bq4847 no SRAM bq4842 with 128K bq4852 with 512K If you use the bq4847 the page says you have to use an external SRAM, but no part is suggested or specified, so I'm not sure where the use of the M68Z512W 3.3V part came from. But again, I would highly suggest finding a real 5V SRAM, or you risk very unreliable operation and early failure. Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4491974 Share on other sites More sharing options...
Shift838 Posted March 27, 2020 Author Share Posted March 27, 2020 (edited) 3 hours ago, matthew180 said: I assume the design is coming from the TI Tech Pages? http://www.nouspikel.com/ti99/titechpages.htm A quick check and I don't see any specific SRAM called out, only the clock IC, and the strange combined clock+SRAM ICs: bq4847 no SRAM bq4842 with 128K bq4852 with 512K If you use the bq4847 the page says you have to use an external SRAM, but no part is suggested or specified, so I'm not sure where the use of the M68Z512W 3.3V part came from. But again, I would highly suggest finding a real 5V SRAM, or you risk very unreliable operation and early failure. the SRAM part number came from the component list off of Thierry's site. HERE Edited March 27, 2020 by Shift838 Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4492133 Share on other sites More sharing options...
matthew180 Posted March 27, 2020 Share Posted March 27, 2020 Ah, right, I missed that table the second time through the page (in too big of a hurry). I suspect Thierry never actually built his board with that SRAM and probably did not realize it was a 3.3V only device when he found it to list as an alternative. You could email and ask him though. But either way, the datasheet specifies it is a 3.3V device, and the I/O will only tolerate 3.6V max (i.e. it is *not* 5V TTL tolerant). Personally I would not use it on this 5V only board, it will not last very long. Even if you had a 3.3V Vcc for the SRAM, its I/O is still not rated to interface with the other 5V parts. 1 Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4492189 Share on other sites More sharing options...
Shift838 Posted March 27, 2020 Author Share Posted March 27, 2020 7 hours ago, matthew180 said: Ah, right, I missed that table the second time through the page (in too big of a hurry). I suspect Thierry never actually built his board with that SRAM and probably did not realize it was a 3.3V only device when he found it to list as an alternative. You could email and ask him though. But either way, the datasheet specifies it is a 3.3V device, and the I/O will only tolerate 3.6V max (i.e. it is *not* 5V TTL tolerant). Personally I would not use it on this 5V only board, it will not last very long. Even if you had a 3.3V Vcc for the SRAM, its I/O is still not rated to interface with the other 5V parts. Does anyone have Thierry's current email address as the one on his page is not valid. Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4492351 Share on other sites More sharing options...
+Lee Stewart Posted March 27, 2020 Share Posted March 27, 2020 4 hours ago, Shift838 said: Does anyone have Thierry's current email address as the one on his page is not valid. I am a little surprised his Yahoo address is no longer valid. It was for me four years ago. ...lee 1 Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4492642 Share on other sites More sharing options...
Asmusr Posted March 27, 2020 Share Posted March 27, 2020 (edited) 1 hour ago, Lee Stewart said: four years ago is a long time... He is probably occupied with corona virus now. https://www.hug-ge.ch/medecine-genetique/equipe-du-service-medecine-genetique Edited March 27, 2020 by Asmusr 2 Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4492655 Share on other sites More sharing options...
matthew180 Posted March 27, 2020 Share Posted March 27, 2020 Alternatively just believe the datasheet for the part and conclude that a 3.3V device will probably be damaged in a 5V circuit. Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4492889 Share on other sites More sharing options...
atrax27407 Posted March 28, 2020 Share Posted March 28, 2020 This address was good for Thierry a couple of months ago: nouspikel@yahoo.com Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4492913 Share on other sites More sharing options...
brain Posted March 28, 2020 Share Posted March 28, 2020 It looks like he used the alternative part from Mouser, the TC554001AFT-70, which is 5V: https://html.alldatasheet.com/html-pdf/31696/TOSHIBA/TC554001AFT-70/253/1/TC554001AFT-70.html Just find a replacement for that IC and all is well. If you're more adventurous and have the space to make a through hole board, it looks like it could be made through hole, and Alliance makes a 32 pin DIP 5V 512kB SRAM. Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4492916 Share on other sites More sharing options...
F.G. Kaal Posted March 28, 2020 Share Posted March 28, 2020 9 hours ago, matthew180 said: Alternatively just believe the datasheet for the part and conclude that a 3.3V device will probably be damaged in a 5V circuit. In Thierry's design the RAM chip M68Z512W get its power from the clock chip BQ4847 chip (pin #1 Vout) . See also schematic in my website http://www.ti99-geek.nl/Projects/idecard/Files/ide_sch2.gif When using the other clock chip BQ4842 you don't need the RAM chip ... the DSR can be stored in the clock cips memory. If the RAM chip is added anyway then yo have to disable it when using this clock chip. In the data sheet of the RTC-65271 I don't see a voltage output for some external device. If this clock chip is going to be used some batery backup for the RAM chip must be created. Fred ;- Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4493202 Share on other sites More sharing options...
Swim Posted March 28, 2020 Share Posted March 28, 2020 10 hours ago, F.G. Kaal said: In Thierry's design the RAM chip M68Z512W get its power from the clock chip BQ4847 chip (pin #1 Vout) . See also schematic in my website http://www.ti99-geek.nl/Projects/idecard/Files/ide_sch2.gif When using the other clock chip BQ4842 you don't need the RAM chip ... the DSR can be stored in the clock cips memory. If the RAM chip is added anyway then yo have to disable it when using this clock chip. In the data sheet of the RTC-65271 I don't see a voltage output for some external device. If this clock chip is going to be used some batery backup for the RAM chip must be created. Fred ;- Hi Fred, there is supply of BQ4852YMC-85 but Rochester electronics instead of no longer available Texas Instruments. https://www.digikey.com/product-detail/en/rochester-electronics-llc/BQ4852YMC-85/2156-BQ4852YMC-85-TI-ND/11538020 Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4493813 Share on other sites More sharing options...
matthew180 Posted March 28, 2020 Share Posted March 28, 2020 11 hours ago, F.G. Kaal said: In Thierry's design the RAM chip M68Z512W get its power from the clock chip BQ4847 chip (pin #1 Vout) . Vout is the same as Vcc (5V) during normal operation, and switches to the battery voltage (probably about 3V) when power is lost. But the normal operation voltage is still 5V, and this does not address the I/O signals that are still going to be coming from 5V TTL ICs. 27 minutes ago, Swim said: ... there is supply of BQ4852YMC-85 but Rochester electronics ... Those do not provide the battery Vout to power the external SRAM during power failure, if that is important. Also, any of these clock chips with internal batteries are going to suffer the same problem, i.e. they will be dead in 10 years, which in retro-computing is not very long. And in 10 years they will probably be near impossible to get. Using an external battery design would be a better option, IMO. Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4493858 Share on other sites More sharing options...
Swim Posted March 28, 2020 Share Posted March 28, 2020 24 minutes ago, matthew180 said: Vout is the same as Vcc (5V) during normal operation, and switches to the battery voltage (probably about 3V) when power is lost. But the normal operation voltage is still 5V, and this does not address the I/O signals that are still going to be coming from 5V TTL ICs. Those do not provide the battery Vout to power the external SRAM during power failure, if that is important. Also, any of these clock chips with internal batteries are going to suffer the same problem, i.e. they will be dead in 10 years, which in retro-computing is not very long. And in 10 years they will probably be near impossible to get. Using an external battery design would be a better option, IMO. Hi matthew180, the BQ4852YMC-85 carries the 512k SRAM on board so there is no need for a 512k SRAM at location IC23. Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4493895 Share on other sites More sharing options...
brain Posted March 28, 2020 Share Posted March 28, 2020 I'd possibly be willing to redo the schematic and PCB and make it all through hole, but I'd need help... If I did, I'd probably make the entire design through hole parts, since I don't know that I see any reason it all has to be surface mount. 1 Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4493899 Share on other sites More sharing options...
matthew180 Posted March 28, 2020 Share Posted March 28, 2020 5 minutes ago, Swim said: ... the BQ4852YMC-85 carries the 512k SRAM on board ... Ah, yeah, right. Too many options, too easy to make a mistake. Even with the internal SRAM, the internal battery is going to be a problem down the road. 1 Quote Link to comment https://forums.atariage.com/topic/304302-suitable-sram-replacement/#findComment-4493901 Share on other sites More sharing options...
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