Advanced Quarter Megabyte RAM - Preliminary

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daveejhitchins
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Advanced Quarter Megabyte RAM - Preliminary

Post by daveejhitchins » Thu Nov 08, 2012 8:51 pm

Well, actually it a 512K RAM . . .

This project is based on the original product. Attached is the user guide for it.

The original design used 8 x 256K DRAM plus all the associated glue logic (from my scribbles it contained 2 x PLD + . . .). Unfortunately I don't seem to be able to find the original circuit diagram - I just have a folder containing scribbled notes and lots of catalogues of delay lines.

If anyone ever comes across one of these cartridges Please [-o< let me borrow it for a week (I'll pay all expenses, of course).

So, this reincarnation . . . And why am I bothering? Well, the last is easy to answer: Because I can, and more importantly, because I want to. I'm trying to recreate the whole catalogue of products from the 80's/early 90's. Just so they don't die a death - Suppose some may call it vanity - don't know (don't care :D). And now, this reincarnation . . . Of course, it has to be different. Not having the original schematics, and, why would you want to use DRAM anymore :lol: However, I also want to make it LOOK as near as possible, electrically, to the original as there is supporting routines in some of the ACP products. I'll need to investigate this as I don't remember all the details - once more, no surprise there :D

Swapped the DRAM for 512K SRAM (couldn't find a suitable 256K version). It'll be based on the ABR schematic, as you'll see below. I don't think I'll need 2 x PLD here though. I've had a good thinking session today and what is in the below schematic should suffice. I'll need to reconfigure the CUPL equations, but shouldn't be too much of a problem? The benefit, of course, is we'll have a battery backed version, similar to the ABR.

One point I'm pondering over is the locking mechanism and the paging register . . . The ABR can lock each 'visible' image bank (2 x 16K) individually. The AQMR, however, couldn't! I'm not sure why not - possibly lack of space in the PLDs? Or, was it down to how the paging register worked. E.g. did you only see one 16K block at a time? The below schematic would allow 2 x 16K blocks to be seen at a time. To be fully compatible, with any existing ROMs, I'll need to answer this question. There may be a way of incorporating the best of both worlds - especially as I'm using 512K here. I could provide (need to look into this more closely!) a lock for both visible banks, ensuring that the default bank used the original lock/unlock addresses. Any ROM utilities wouldn't know about the 'other' bank and, hopefully, would work OK. Any thoughts on this would be appreciated :D

Anyway, here's a quick view of the schematic - with the full one attached.Not complete!

As usual, any feedback, positive or negative :cry: is always appreciated . . .

Note: For convenience I've added the paging register address and lock/unlock addresses below the CUPL equations.

Dave H :D

Edit: Schematic - wrong one, removed.
Attachments
Advanced Quarter Meg RAM.pdf.zip
(76.64 KiB) Downloaded 80 times
Last edited by daveejhitchins on Thu Sep 21, 2017 9:10 pm, edited 1 time in total.
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
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pstnotpd
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Re: Advanced Quarter Megabyte RAM - Preliminary

Post by pstnotpd » Fri Nov 09, 2012 6:39 am

I'm certainly interested in this one!

Didn't know these existed in the first place, and electron compatible no less.
Had I know back in the 80s.... I probably wouldn't have been able to pay for it

Are you going commercial with all this, or perhaps under the retrosoftware flag?

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Re: Advanced Quarter Megabyte RAM - Preliminary

Post by daveejhitchins » Fri Nov 09, 2012 8:06 am

pstnotpd wrote:Are you going commercial with all this, or perhaps under the retrosoftware flag?
Well, commercial in the sense that I'll be providing kits and built units, but not to make money - just a great hobby now :D

Dave H :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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Re: Advanced Quarter Megabyte RAM - Preliminary

Post by daveejhitchins » Mon Jan 21, 2013 11:39 pm

Prototype board for building and testing:
AQMR 1.jpg
AQMR 1.jpg (359.11 KiB) Viewed 592 times
AQMR 2.jpg
AQMR 2.jpg (335.68 KiB) Viewed 592 times
More details later.

Dave H :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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Re: Advanced Quarter Megabyte RAM - Preliminary

Post by 1024MAK » Tue Jan 22, 2013 12:31 am

With all these great items soon to become available, I'd best start counting me money :lol:
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Re: Advanced Quarter Megabyte RAM - Preliminary

Post by Haqa » Tue Jan 22, 2013 12:40 am

This looks really interesting. I assume it's for the master currently, are there any plans to make something for a plain B?

H.
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Re: Advanced Quarter Megabyte RAM - Preliminary

Post by daveejhitchins » Tue Jan 22, 2013 7:47 am

Haqa wrote:This looks really interesting. I assume it's for the master currently, are there any plans to make something for a plain B?
H.
All, except the Tube interface, will work in both the Master and the Electron. I did have a BBC version, very late in day. I don't remember much about it other than it used the usual wires with EZ hooks on the end. Unfortunately I haven't found any details at all! Maybe this can be a future project. I'll keep me off the streets, so to speak :lol:

Dave H :D

p.s. It was an ABR by the way.
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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Re: Advanced Quarter Megabyte RAM - Preliminary

Post by peterj » Tue Jan 22, 2013 12:18 pm

daveejhitchins wrote:Prototype board for building and testing:
AQMR 1.jpg
AQMR 2.jpg
More details later.

Dave H :D
Hi Dave.

I was thinking if a small right angle riser would allow it to fit in the rearmost cartridge socket and still allow you to fit the top lid of the Master back on.

Peter

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Re: Advanced Quarter Megabyte RAM - Preliminary

Post by daveejhitchins » Tue Jan 22, 2013 6:41 pm

Hi Dave.

I was thinking if a small right angle riser would allow it to fit in the rearmost cartridge socket and still allow you to fit the top lid of the Master back on.

Peter
I sure we can sort something out, Peter. When I get-back from my week with # 4 grandchild and some serious Photography catch-up, I'll open my Master and give it a once over to see what space there is. Shouldn't be too much of a problem :wink:

And, while I'm here: Here's the BoM with RS prices for the AQMR board.

Dave H :D
Advanced Quarter Meg RAM BoM - 22-01-13.xls.zip
(10.76 KiB) Downloaded 50 times
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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Re: Advanced Quarter Megabyte RAM - Preliminary

Post by daveejhitchins » Thu Sep 21, 2017 9:45 pm

Hmmm! Just picked this thread again :-k Either I was on-something in 2013 or all the attachments have been screwed!

I start off here talking about the AQR but all but one of the attachments I've posted are to do with the ABR :shock:

So to pick-up the thread, here are some photo of the AQR. Kindly taken by Paul (DutchAcorn). I hope, with his assistance, I can reverse engineer the schematic.

I found a folder, today, that contains a BoM, PLD equations and lots of data on the individual parts used - No Schematic, however. I need to set-up a retro PC and get my original CAD package (PCAD) up and running, as I have lots of discs that, probably, contain all the original designs . . .

Here are the Photos:
AQR Case Front.jpg
AQR Case Top.jpg
AQR PCB Front 1.jpg
AQR PCB Back.jpg
AQR PCB Front 2.jpg
AQR PCB Front 3.jpg
Dave H :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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Re: Advanced Quarter Megabyte RAM - Preliminary

Post by Pernod » Sat Jan 27, 2018 11:59 am

Could someone that has an AQR do a quick experiment for me? Since the AQR only exposes a single 16K page at a time and the cartridge slot handles two pages, which page does the AQR use, ie. ROMQA high or low? Or does it ignore the ROMQA line and the Electron sees both pages populated?

Just load a ROM image into the AQR and do *ROMS. Thanks.
- Nigel

BBC Model B, ATPL Sidewise, Acorn Speech, 2xWatford Floppy Drives, AMX Mouse, Viglen case, BeebZIF, etc.

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Re: Advanced Quarter Megabyte RAM - Preliminary

Post by DutchAcorn » Sat Jan 27, 2018 7:09 pm

I don’t own an Electron currently, but the Master just shows the loaded ROMs twice, regardless of the ROM bank I use. So it sees both pages populated.
Paul

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Re: Advanced Quarter Megabyte RAM - Preliminary

Post by Pernod » Sat Jan 27, 2018 7:12 pm

DutchAcorn wrote:I don’t own an Electron currently, but the Master just shows the loaded ROMs twice, regardless of the ROM bank I use. So it sees both pages populated.
Thanks, I kinda expected that. So ROMQA is not connected.
- Nigel

BBC Model B, ATPL Sidewise, Acorn Speech, 2xWatford Floppy Drives, AMX Mouse, Viglen case, BeebZIF, etc.

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Re: Advanced Quarter Megabyte RAM - Preliminary

Post by daveejhitchins » Sun Jan 28, 2018 9:43 am

That would make since, as QA isn't connected - A16 - counting from the +5V (the short one) on the component side. I probably didn't have a pin spare on the PLDs!

Dave H :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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