Welcome, Guest. Please login or register.


Author Topic: Internal memory expansion (Read 51169 times)

Offline Saint

  • EP user
  • *
  • Posts: 266
  • Country: gb
  • OS:
  • Mac OS X Mac OS X
  • Browser:
  • Safari 6.0 Safari 6.0
    • View Profile
Re: Internal memory expansion
« Reply #75 on: 2013.October.19. 23:35:22 »
Btw, what's about GALs in general? It seems it's harder and harder to get, since GALs are treated as "old technology", everybody suggests use CPLDs instead, but there are few ones which are 5V ones (or at least 5V tolerant I/O) and DIP packaged ... Also sometimes CPLDs feel a bit "too much" for simplier projects ...

Yes, sadly I don't think they are manufactured any more. They are certainly marked as discontinued on the Lattice data sheets.

I agree a CPLD seems an overkill in many cases, a GAL is perfect for these old hardware projects, and more than powerful enough.

I think I am going to order quite a few GAL chips from China while I can still get them cheaply - cheaper than I can get a CPLD! I know I will find a use for them all one day... :)

Offline Saint

  • EP user
  • *
  • Posts: 266
  • Country: gb
  • OS:
  • Mac OS X Mac OS X
  • Browser:
  • Safari 6.0 Safari 6.0
    • View Profile
Re: Internal memory expansion
« Reply #76 on: 2013.October.19. 23:57:49 »
So what can be more cool than this internal 512KB expansion is a 1MB or 2MB internal expansion ... :)

Hehe, more is always better! :) I could certainly do a 1mb or 2mb expansion using multiple 512kb SRAM chips and expand the GAL to provide the correct chip enable for each SRAM.

Or you could modify the existing SRAM board by soldering the SRAM directly to the board without a socket (to give extra clearance) and piggy back another SRAM on the top. With a modified GAL you could use another output to provide the chip select for the 2nd SRAM with a piece of wire between the GAL leg and the SRAM chip select leg.

I might give this a go if there is any interest? :D 512KB is enough for me, but I could possibly provide a 1mb board for £20... I'd just need to make sure there is enough clearance in the case.

Offline lgb

  • EP addict
  • *
  • Posts: 3496
  • Country: hu
  • æðsta yfirmaður
  • OS:
  • Linux Linux
  • Browser:
  • Chrome 31.0.1650.26 Chrome 31.0.1650.26
    • View Profile
    • http://lgb.hu/
Re: Internal memory expansion
« Reply #77 on: 2013.October.20. 01:07:12 »
Quote from: Saint
I think I am going to order quite a few GAL chips from China while I can still get them cheaply - cheaper than I can get a CPLD! I know I will find a use for them all one day... :)

Can I ask where (and how) you order those GALs (and maybe the SRAM) exactly? Or is it some kind of "secret source"? :) It seems even more regular parts (like 512K SRAM) is quite hard to find sometimes now, especially in DIP packages. A year ago or so, almost every shops had it (here, in Hungary), now I can feel that it's truely more rare (surely it is not impossible _yet_, but ...) and I guess this tendency will continue, so it's better to switch to new source. Can you suggest something, or do you mean general ebay random searches or so when you wrote "China"? I always afraid of China stuffs, but I have no experience at all in these kind of orders (from abroad of Hungary).

Offline Zozosoft

  • EP addict
  • *
  • Posts: 13313
  • Country: hu
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 24.0 Firefox 24.0
    • View Profile
    • http://enterprise.iko.hu/
Re: Internal memory expansion
« Reply #78 on: 2013.October.20. 01:19:58 »
Quote from: Saint
Or you could modify the existing SRAM board by soldering the SRAM directly to the board without a socket (to give extra clearance) and piggy back another SRAM on the top. With a modified GAL you could use another output to provide the chip select for the 2nd SRAM with a piece of wire between the GAL leg and the SRAM chip select leg.
Good idea!

Offline Z80System

  • EP addict
  • *
  • Posts: 3837
  • Country: hu
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Chrome 30.0.1599.101 Chrome 30.0.1599.101
    • View Profile
Re: Internal memory expansion
« Reply #79 on: 2013.October.20. 01:22:59 »
Quote
I might give this a go if there is any interest?  512KB is enough for me, but I could possibly provide a 1mb board for £20... I'd just need to make sure there is enough clearance in the case.


I did not understand the details of the changes exactly,
but if you can build an expansion with 1 mb easily, and there is enough space, and the assembling on the user side is not more complex than the 512KB ones, then the £5 extra price is very good for me.

So in this case one of the "hungarian" boards could be 1MB.
Z80 System

Offline Saint

  • EP user
  • *
  • Posts: 266
  • Country: gb
  • OS:
  • Mac OS X Mac OS X
  • Browser:
  • Safari 6.0 Safari 6.0
    • View Profile
Re: Internal memory expansion
« Reply #80 on: 2013.October.20. 14:28:42 »
Can I ask where (and how) you order those GALs (and maybe the SRAM) exactly? Or is it some kind of "secret source"? :)

I just search eBay for components from international sellers. For GAL's I found these - http://www.ebay.co.uk/itm/10PCS-IC-GAL16V8D-GAL16V8D-25LP-DIP-20-NEW-GOOD-QYALITY-tracking-number-/300920600072?pt=LH_DefaultDomain_0&hash=item461043f608

I've had no problems ordering from overseas sellers so far, other than it can sometimes take a long time to arrive!! :)

I have also been trying surface mount components, but soldering with a soldering iron is very hard for SMD. So I have bought myself a hot air rework station, but it need some practice with solder paste...
« Last Edit: 2013.October.20. 14:35:23 by Saint »

Offline Saint

  • EP user
  • *
  • Posts: 266
  • Country: gb
  • OS:
  • Mac OS X Mac OS X
  • Browser:
  • Safari 6.0 Safari 6.0
    • View Profile
Re: Internal memory expansion
« Reply #81 on: 2013.October.20. 14:30:13 »
So in this case one of the "hungarian" boards could be 1MB.

I will try!! :)

Offline Zozosoft

  • EP addict
  • *
  • Posts: 13313
  • Country: hu
  • OS:
  • Windows XP Windows XP
  • Browser:
  • Firefox 24.0 Firefox 24.0
    • View Profile
    • http://enterprise.iko.hu/
Re: Internal memory expansion
« Reply #82 on: 2013.October.21. 10:28:53 »
Update: Current orders from Hungary: 10!

Offline Saint

  • EP user
  • *
  • Posts: 266
  • Country: gb
  • OS:
  • Mac OS X Mac OS X
  • Browser:
  • Safari 6.0 Safari 6.0
    • View Profile
Re: Internal memory expansion
« Reply #83 on: 2013.October.21. 23:50:18 »
Thanks for the update Zozo! :)

I've made up another 4 boards tonight, I'll test them tomorrow and then Bruce and fatbob_gb are next in line, as all the Hungarian orders will go out together when I get the next batch of PCB's.

Offline Zozosoft

  • EP addict
  • *
  • Posts: 13313
  • Country: hu
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 24.0 Firefox 24.0
    • View Profile
    • http://enterprise.iko.hu/
Re: Internal memory expansion
« Reply #84 on: 2013.October.22. 07:25:32 »
Quote from: Saint
all the Hungarian orders will go out together when I get the next batch of PCB's.
The 1M version can be chosen? It is a +5 GBP?
I will ask which version wanted.

Offline Saint

  • EP user
  • *
  • Posts: 266
  • Country: gb
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Chrome 30.0.1599.101 Chrome 30.0.1599.101
    • View Profile
Re: Internal memory expansion
« Reply #85 on: 2013.October.22. 10:29:54 »
Quote from: Zozosoft
The 1M version can be chosen? It is a +5 GBP?
I will ask which version wanted.
Yes, if you would like to find out how many 1MB / 512KB versions people would like, I will try and got those built. I've checked the clearance, and it looks ok to me, so the only thing left to do is to program a different GAL and hook up a bit of wire for the 2nd chip select. And, yes, I can do the 1MB for £20.

My only concern is heat in the bottom SRAM chip as it will have no ventilation with the 2nd SRAM on top of it. The chip will run up to 85 degrees centigrade according to the datasheet, though, so I don't think it should be a problem. The SRAM was only slightly warm in testing.

Offline lgb

  • EP addict
  • *
  • Posts: 3496
  • Country: hu
  • æðsta yfirmaður
  • OS:
  • Linux Linux
  • Browser:
  • Chrome 31.0.1650.26 Chrome 31.0.1650.26
    • View Profile
    • http://lgb.hu/
Re: Internal memory expansion
« Reply #86 on: 2013.October.22. 10:39:02 »
Quote from: Saint
Yes, if you would like to find out how many 1MB / 512KB versions people would like, I will try and got those built. I've checked the clearance, and it looks ok to me, so the only thing left to do is to program a different GAL and hook up a bit of wire for the 2nd chip select. And, yes, I can do the 1MB for £20.

My only concern is heat in the bottom SRAM chip as it will have no ventilation with the 2nd SRAM on top of it. The chip will run up to 85 degrees centigrade according to the datasheet, though, so I don't think it should be a problem. The SRAM was only slightly warm in testing.

I have no idea about the temperature and the datasheet in this case, but maybe - in general - the "worst" temperature is at the boundary of working conditions ie, very rapid r/w access near the max speed of the memory, as the needed curren to supply on Vcc is related to the frequency in general (and temperature is related the current after tall, emitted heat because of the resistance, etc). So if your SRAM is 70ns I doubt it will be near to 85 degrees if the memory accesses in general occurs more rarely than 70ns ... Well, at least if that number of 85 is defined for the maximum temperature at the most "extreme" usage given by the specification.

Offline Zozosoft

  • EP addict
  • *
  • Posts: 13313
  • Country: hu
  • OS:
  • Windows XP Windows XP
  • Browser:
  • Firefox 24.0 Firefox 24.0
    • View Profile
    • http://enterprise.iko.hu/
Re: Internal memory expansion
« Reply #87 on: 2013.October.22. 10:42:17 »
Quote from: Saint

 so I don't think it should be a problem.
Strange example :-) (Once I found 8x 8K SRAM chips in a old PCB, and built a 64K expansion for my EP :-D )

Offline Saint

  • EP user
  • *
  • Posts: 266
  • Country: gb
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Chrome 30.0.1599.101 Chrome 30.0.1599.101
    • View Profile
Re: Internal memory expansion
« Reply #88 on: 2013.October.22. 10:48:43 »
Quote from: lgb
I have no idea about the temperature and the datasheet in this case, but maybe - in general - the "worst" temperature is at the boundary of working conditions ie, very rapid r/w access near the max speed of the memory, as the needed curren to supply on Vcc is related to the frequency in general (and temperature is related the current after tall, emitted heat because of the resistance, etc). So if your SRAM is 70ns I doubt it will be near to 85 degrees if the memory accesses in general occurs more rarely than 70ns ... Well, at least if that number of 85 is defined for the maximum temperature at the most "extreme" usage given by the specification.
Yes, I agree. The SRAM is actually 55ns, so it is running way below it's maximum frequency, and will be drawing more current while switching. So it should be running cool compared to what it can do.

Zozo: Wow, that chip stack is awesome! :D

Offline Zozosoft

  • EP addict
  • *
  • Posts: 13313
  • Country: hu
  • OS:
  • Windows XP Windows XP
  • Browser:
  • Firefox 24.0 Firefox 24.0
    • View Profile
    • http://enterprise.iko.hu/
Re: Internal memory expansion
« Reply #89 on: 2013.October.22. 11:01:29 »
Quote from: Saint
The SRAM is actually 55ns
I hope it is will be enought fast for 10MHz Z80!