YARRB

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roland
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YARRB

Postby roland » Sat Jun 25, 2016 9:57 pm

YARRB = Yet Another Ram/Rom Board

For my Acorn Atom Blue I have designed another Ram/rom board. Why? Just because I want a memory extension for my classic Atoms that offer as much memory and possibilities as the Atom2015 has. So this board has 128kB of ram and 32kB of rom. It also offers three cpu clock speeds: 1, 2 and 4 MHz.

The memory map is:

#0000 - #3FFF: 16 kB
#4000 - #7FFF: 4 * 16 kB
#A000 - #AFFF: 8 * 4 kB
#C000 - #FFFF: 16 kB
Total: 128 kB RAM

Rom: 2 x 16kB #C000 - #FFFF

Besides the cpu clock speed it also offers a control signal for the Atom bus buffers. In de power-on default I want to select AtoMMC rom at #Exxx but when the second ROM-bank (with AtomDOS at #Exxx) is selected, the board should disable memory at #0Axx and enable the Atom bus for accessing the 8271 FDC controller of the disc controller board.

Installing the board will be a matter of removing a bunch of IC's and adding two wires on the Atom main board. Probably no breaking of tracks or other scary stuff on the Atom's main board. This board will be installed in the 6502 socket so it leaves the PL6/7 connectors free for more exiting purposes like a 80 column board or a matchbox copro.

Why not using Prime's board? Well, simply because it has no RAM to load an operating system and there's only one bank of RAM at #Axxx. Sure, you don't need to *INIT the Atom to load all the roms, but I like the flexibility of loading the rom. That's my humble opinion.

In the attached PDF files you can have a preview of the designs. Enjoy reading!
Attachments
yarrb-pcb.pdf
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yarrb-sch.pdf
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Re: YARRB

Postby hoglet » Sat Jun 25, 2016 10:13 pm

Hi Roland,

I think it's really great that you are doing this - the more addons we have for the Atom the better.

I have a couple of suggestions to make life more interesting!

1. Allow for a 32-pin, 128KB (1Mbit) FLASH ROM to be used (i.e. two extra address lines).

2. Wire up the WE signal as well (maybe through a jumper), and then individual banks of the FLASH could be re-programmed in-system

If you look at the pinout of the 28F010 here, I think you can easily accommodate both 28-pin and 32-pin devices.

By doing this, you could avoid the need to boot the Atom, yet still have all the flexibility of loading the OS into RAM, etc. There would also be space to have an alternative OS, like BBC Basic, always available.

Why do all this? Two reasons:
- It makes the board more useful, even if you don't have an AtoMMC fitted (e.g. for floppy disk-only systems)
- It removed the slight annoyance of having to "boot" the Atom

Dave

P.S. I'm wondering if doing the above as a "mod" to my Atom2015 would be possible

P.P.S Have you checked if the board will physically clash with Phill's Colour board?

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Re: YARRB

Postby roland » Sat Jun 25, 2016 11:03 pm

Thanks Dave for your comments. I have two questions:

Are all colour boards by Phill the same size? If not I'd like to see a picture of the largest board fitted in an Atom.

Do the colour boards need a 1.79 MHz signal for NKen? This is lacking on my board.

I'll have a look about the 28F010.
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Re: YARRB

Postby hoglet » Sun Jun 26, 2016 5:20 am

roland wrote:Are all colour boards by Phill the same size? If not I'd like to see a picture of the largest board fitted in an Atom.

I'll let Phill answer that.

He has some pictures here (facebook)

Here's a photo of mine in my original Atom:
IMG_2194.JPG

roland wrote:Do the colour boards need a 1.79 MHz signal for NKen? This is lacking on my board.

This would only make sense if you were able to clock the 6502 off a half speed video clock at 1.79MHz.

The signal for NHen is high if the 6502 is clocked at 1.79 (to disable the noise killer), and low at all other speeds.

I have doubts anyway that the noise killer would function correctly at 2 and 4 MHz.
roland wrote:I'll have a look about the 28F010.

Actually, the one to check out, which I use on AtomFPGA, and which Phill uses on his boards, is the Microchip 39SF010A

I think the both have the same pinout.

The software to re-program the 39SF101A is already built into the FPGA Utils ROM.

By the way, the current Atom FPGA also works exactly identically to a 2015 Atom.

Dave

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Re: YARRB

Postby hoglet » Sun Jun 26, 2016 5:32 am

And another of just the RAMROM board:
IMG_0367.JPG

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Re: YARRB

Postby roland » Sun Jun 26, 2016 5:38 pm

I have updated the board so it can either have a 27256 Eprom or a 128k flash rom. If an eprom is used then a connection has to be made between pin 32 and 30 of the socket. WE and Vpp can be connected via a jumper or wire bridge.

The board is reaches just until the 8255 so it doesn't clash with the colour board.

IMG_1084.JPG


There are two challenges for this design:
1. How to map all this memory in the Atom memory map :?:
2. How will I program the first OS version into the flash rom :)
Attachments
yarrb-sch.pdf
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yarrb-pcb.pdf
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Re: YARRB

Postby IanS » Sun Jun 26, 2016 5:54 pm

The circuit diagram has a 28F010 on it and a jumper for Vpp. The 28F010 requires 12V for programming.

As suggested, look at the 39SF010 (4k page size) or 29C010 (128 bytes page size). Can you add another two address lines (A17,A18) to allow 39SF040 (or 29C040) to be fitted? Rom Filling system for the Atom?

29C010 - http://www.futurlec.com/Datasheet/Memory/AT29C010.pdf

Ian.

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Re: YARRB

Postby hoglet » Sun Jun 26, 2016 6:04 pm

roland wrote:1. How to map all this memory in the Atom memory map :?:

Can't you just extend the use of Bit 2 of #BFFE:

Code: Select all

bit 2: OS ROM/RAM select
You can turn off the eprom to get more RAM, or even better: load a modified or another operating system without swapping the eprom.
0: OS running in ROM
1: OS running in RAM

You could split the 128KB ROM into two banks of 64KB selected by the Bank Select bit (#BFFF bit 3)

Each bank could contain:
0000-7FFF (32KB) paged ROMs, mapped to #A000-#AFFF in the Atom memory map
8000-BFFF (16KB) unused
C000-FFFF (16KB) OS, mapped to #C000-#FFFF in the Atom memory map (e.g. Basic, FP, AtoMMC, OS)

Also, take a look at how Kees and I modified the CPLD in Phill's RAMROM board (and Atomulator) to support a BBC Basic Mode. There was a nice write-up of this somewhere, which I'll try to locate.
roland wrote:2. How will I program the first OS version into the flash rom :)

Many EPROM programmers will also program 5V FLASH devices.

Which ones do you have?

I use a Genuis G540, like this one, which was pretty cheap:
http://www.ebay.co.uk/itm/Genius-G540-U ... Sw0t9U13~0

Alternatively, I wonder if a "Bootstrap" mode would be possible, that would use the original Atom OS/Basic, and just load a programming program (and OS to be programmed) from Tape. Fun, but probably unnecessary.


Dave

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Re: YARRB

Postby hoglet » Sun Jun 26, 2016 6:11 pm

Here's a link that shows how the 128KB of FLASH is allocated in the modified CPLD version Kees and I are running:
viewtopic.php?f=44&t=8350&start=60#p92948

It supports three different modes:
- Atom mode with MMC
- Atom mode with DOS
- BBC mode

An alternative set of "paged" ROMs are available in BBC Mode.

This is also what the latest version of Atomulator uses as a 128KB ROM image.

It does appear we have two very different organizations for #BFFE

I wonder if there is a way to somehow bring them back together into a kind-of super-set.

Do you currently have any spare bits in the #BFFE in the New Atom?

Dave

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Re: YARRB

Postby roland » Sun Jun 26, 2016 6:21 pm

At the moment I don't have any spare bits at #BFFE. But I think #BFFF has some. I could move the write protect bit for the RAM to bit 5 of #BFFF and OS RAM/ROM select to bit 7. Bit 3 (bank select ROM) might be obsolete so that gives three spare bits at #BFFE.
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Re: YARRB

Postby roland » Sun Jun 26, 2016 7:26 pm

IanS wrote:The circuit diagram has a 28F010 on it and a jumper for Vpp. The 28F010 requires 12V for programming.


Yeah, I noticed that (after reading your post) :oops:

However, I have an explanation. Pin 44 of the CPLD can be used as an output to drive a transistor that will switch on and off the external 12V for reprogramming the eeprom. You don't have to put a jumper over there, it can also handle two pieces of wire :mrgreen: Probably no one will use that feature but it is possible.

IanS wrote:As suggested, look at the 39SF010 (4k page size) or 29C010 (128 bytes page size).


Both of them can be used in the current design. I will add those numbers to the diagram.

IanS wrote:Can you add another two address lines (A17,A18) to allow 39SF040 (or 29C040) to be fitted? Rom Filling system for the Atom?


The address lines RA17 and RA18 should be driven from the CPLD and in the current design there is no free pin left. The great advantage of using a CPLD is that you can change the internal design (or code). If you don't need the Bus_enable and Vpp than you can use these for A17 and A18. In that case using a 39SF040 is just a matter of reprogramming your CPLD and add two pieces of wire. A non-destructive and reversible operation.
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Re: YARRB

Postby roland » Tue Jun 28, 2016 8:40 pm

I have been thinking about the memory mapping in this board.

Is it a good idea to use bit 7 of #BFFF for switching between the RAM/ROM board (0) or Atom2k15 (1) ?

So if bit 7 is 0 then #BFFE behaves like Phill's RAM/ROM board and if it's 1 then #BFFE behaves like the Atom2k15.

When used in RAM/ROM board mode, bits 7 and 6 can still be used for cpu speed selection and bit 5 and 4 for mapping four banks of 16K into #4000 - #7FFF (making 64k of RAM available). The big question is if all this logic fits into a 9572 CPLD. My adapted Atom2k15 design uses these resources:

Code: Select all

** Function Block Resources **

Function    Mcells      FB Inps     Pterms      IO         
Block       Used/Tot    Used/Tot    Used/Tot    Used/Tot   
FB1          10/18       22/54       33/90       9/ 9*
FB2          14/18       24/54       39/90       8/ 9
FB3          14/18       24/54       64/90       9/ 9*
FB4           1/18        9/54        1/90       7/ 7*
             -----       -----       -----      -----   
             39/72       79/216     137/360     33/34

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Re: YARRB

Postby roland » Tue Jun 28, 2016 8:46 pm

roland wrote:I have been thinking about the memory mapping in this board.

Is it a good idea to use bit 7 of #BFFF for switching between the RAM/ROM board (0) or Atom2k15 (1) ?

So if bit 7 is 0 then #BFFE behaves like Phill's RAM/ROM board and if it's 1 then #BFFE behaves like the Atom2k15.

When used in RAM/ROM board mode, bits 7 and 6 can still be used for cpu speed selection and bit 5 and 4 for mapping four banks of 16K into #4000 - #7FFF (making 64k of RAM available). The big question is if all this logic fits into a 9572 CPLD. My adapted Atom2k15 design uses these resources:

Code: Select all

** Function Block Resources **

Function    Mcells      FB Inps     Pterms      IO         
Block       Used/Tot    Used/Tot    Used/Tot    Used/Tot   
FB1          10/18       22/54       33/90       9/ 9*
FB2          14/18       24/54       39/90       8/ 9
FB3          14/18       24/54       64/90       9/ 9*
FB4           1/18        9/54        1/90       7/ 7*
             -----       -----       -----      -----   
             39/72       79/216     137/360     33/34



BTW ... how many board shall I order in the first run?
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Re: YARRB

Postby 1024MAK » Tue Jun 28, 2016 9:15 pm

roland wrote:BTW ... how many board shall I order in the first run?

Is this the bit where I vote for one as a protest vote? :lol:


















If you want a sensible answer, well, I'm tempted, so tell me more, and I may cave and claim one :wink:

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Re: YARRB

Postby hoglet » Tue Jun 28, 2016 9:16 pm

roland wrote:Is it a good idea to use bit 7 of #BFFF for switching between the RAM/ROM board (0) or Atom2k15 (1) ?

So if bit 7 is 0 then #BFFE behaves like Phill's RAM/ROM board and if it's 1 then #BFFE behaves like the Atom2k15.

I would be concerned that existing software (like BRAN) would keep accidentally switching modes.

The #A000 ROM loader in AtoMMC would need to be modified as well.

Would it be possible to use a different location (e.g. bit 7 in #BFFD) to switch between the two modes?
roland wrote:The big question is if all this logic fits into a 9572 CPLD.

I'm sure it will be fine.
roland wrote:BTW ... how many board shall I order in the first run?

I would certainly like to acquire one!

Dave

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Re: YARRB

Postby roland » Fri Jul 01, 2016 5:40 pm

I have changed the board a little bit. It is possible now to make a connection from A1 to the CPLD pin 44 (instead of connecting pin 44 to Vpp of the eeprom). This way we could add two registers at #BFFC and #BFFD. If A1 is connected, it should be excluded to the selection of #BFFx at the 74LS133 so there is room for a resistor to pull up this input pin (1).

Please have a final look at the schematic design and pcb and if there are no further comments I'll order a first batch of 5 pieces.
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yarrb-sch.pdf
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yarrb-pcb.pdf
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Re: YARRB

Postby hoglet » Fri Jul 01, 2016 9:27 pm

Hi Roland,

I had a quick look over the schematic earlier in the evening, and it looks good to me.

I can spend a bit more time checking over the weekend if you like.

Do you have any areas of concern?

Dave

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Re: YARRB

Postby roland » Fri Jul 01, 2016 10:18 pm

I have no areas of concern. After all, it is based on the Atom 2k15 memory design and that works also fine.
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Re: YARRB

Postby roland » Sun Jul 03, 2016 1:11 pm

I have ordered five boards and some components to build one. Starting the 4-5 weeks estimated delivery time.

If I had thought about placing the connection to the Atom at the solder side the 3D image would have looked better. Now I have to use a little pressure to squeeze the connector through the 6502 :lol:

Yarrb.png


Another optical mistake is that the flashrom is 39SF010 and not 39FS010 as written in the diagram. I discovered this because no supplier sells a 39FS010.
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Re: YARRB

Postby 1024MAK » Sun Jul 03, 2016 1:47 pm

roland wrote:Now I have to use a little pressure to squeeze the connector through the 6502 :lol:
Sounds painful :lol:

When they have arrived, let me know how much I owe you. Are you going to send all the UK destined boards over to Dave like last time?

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Re: YARRB

Postby roland » Sun Jul 03, 2016 1:54 pm

1024MAK wrote:Are you going to send all the UK destined boards over to Dave like last time?


I might do that if Dave agrees.
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Re: YARRB

Postby hoglet » Sun Jul 03, 2016 1:57 pm

roland wrote:
1024MAK wrote:Are you going to send all the UK destined boards over to Dave like last time?


I might do that if Dave agrees.

Or you could send them to Mark :lol:

... only joking - I'm happy to send them on to UK folk.

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Re: YARRB

Postby roland » Fri Jul 29, 2016 8:59 pm

Now that the pcb's are arrived it's time to pick up this project. I have designed a very basic logic for the CPLD that just enables 32k RAM, 16k ROM and 8 utility roms. This is just for testing purposes. It can also switch between the three clock speeds. With this design I expect to get the board working.

And after I get it working I'll design a new logic that is more advanced. In fact, it will have four different memory profiles. Two of them should be fully compatible with the original RAMROM board. The other two profiles will look like the Atom 2k15 but they are not 100% compatible due to other assignments of the individual bits of #BFFE.

These are the memory profiles:

Code: Select all

Mode            B7      B6      B5      B4      B3      B2         B1          B0
-----------------------------------------------------------------------------------------------------
Atom Ram/rom    -       clk1    clk0    0       0       DskRomEn   DskRamEn    ExtRamEn
Atom BBC        -       clk1    clk0    0       1       -          ExtRamEn2   ExtRamEn1
Atom 2k15       wp      clk1    clk0    1       0       DskRamEn  xma1        xma0
Atom exp        wp      clk1    clk0    1       1       DskRamEn  xma1        xma0


B6 and B5 will always be used for selecting the CPU clock speed. B4 and B3 are the profile-select bits. If you write any value to #BFFE with the upper nibble = 0 then you have the original ramrom board settings. So ?#BFFE=#8 will select BBC Basic.

If B4 = 0 then the board is in classic mode. You have 32k RAM in the lower address space and all the roms are read from the EEPROM.
If B4 = 1 then the board enters the Atom 2k15 mode. In this mode the EEPROM is not used and the Atom has access to the full 128k of RAM memory.

The main difference between mode Atom 2k15 and Atom exp will be the behaviour when break is pressed. If B4 = 1 and B3 = 1 then those bits will both be reset to 0 when break is pressed. In the other modi these bit will not be reset by break. This way you can experiment with kernel software in ram without locking up your Atom (and possibly lose some work when the only option is a power cycle). The clk bits will always be reset to 0 at break.

If the space in the CPLD permits this is the plan that I want to work out. I'll keep you informed about my progress....


Edit: I corrected the usage of the mode select bits and there is no xma2 because there is only 64kB available for XMA, these are four banks of 16k so only two bits are needed. Bit xma2 can now be used to enable/disable ram at #0A00.
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Re: YARRB

Postby sirmorris » Fri Jul 29, 2016 9:13 pm

=D> =D> =D>

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Re: YARRB

Postby 1024MAK » Sat Jul 30, 2016 10:01 am

Nice :D

You say bits 5 and 6 are used for clock selection, okay. But you then talk about bit 5 selecting a memory profile. Did you mean to say bit 4? :?:

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Re: YARRB

Postby Multiwizard » Sat Jul 30, 2016 11:27 am

What SirMorris said... :D

=D> =D> =D>


Greetings, Wim... :-)

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Re: YARRB

Postby roland » Sat Jul 30, 2016 5:21 pm

1024MAK wrote:Nice :D

You say bits 5 and 6 are used for clock selection, okay. But you then talk about bit 5 selecting a memory profile. Did you mean to say bit 4? :?:

Mark


You're right. The mode bits are b4 and b3. I will correct the post when I am at a computer.
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Re: YARRB

Postby oss003 » Sat Jul 30, 2016 6:52 pm

Hi Roland,

sounds like a good plan ........ =D>

The bits of #BFFE are not clear to me:

Code: Select all

DskRomEn  = MMCROM/DOSROM at #Exxx
B0 - ExtRamEn  = RAM/No RAM at #Axxx
B1 - DskRamEn  = RAM/Diskcontroller at #0Axx
B2 - ExtRamEn1 = ROM/RAM MOSEXT1 at #6xxx
ExtRamEn2 = ROM/RAM MOSEXT2 at #7xxx
xma0/1/2  = ???

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Re: YARRB

Postby roland » Sat Jul 30, 2016 9:12 pm

xma is eXtended Memory Access. I used this term in my Atom-in-PC to address up to 4 Mb of XMA memory of the PC. This memory was swapped in and out to #4000 - #7FFF. It was real virtual memory :o With some operating system call you could write a block of 16k to the PC's memory and read another block from the PC's memory into the Atom. This way it looked like we had 4 Mb of extra memory in the Atom.

When I designed the Atom 2k15 (actually it was in the summer of 2014, somewhere in France where the first drawings were made) I assigned 64 kB of memory to #4000 - #7FFF, four blocks of 16kB each. I still called it XMA. It is less memory than in the Atom-in-PC but on the other hand, it is real memory so swapping between the banks is so much faster now.

But, there are only 4 banks of 16kB so I need only two bits (xma0 and xma1) for selecting a bank. The third bit will now be used to enable/disable ram at #A00 so that we can also use a disk drive in this mode.
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Re: YARRB

Postby roland » Sat Jul 30, 2016 9:17 pm

I have some more pictures:

IMG_1174.JPG
This is the PCB fitted into the 6502 socket. First success: it fits. I used this configuration to check the voltages.


IMG_1175.JPG
Completely build and parts fitted.


IMG_1173.JPG
Bottom view of the PCB.


One of these days I will install the jumpers, program the CPLD, remove the Atom's memory and install the board.Hoping for more success stories [-o<
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