Date : Sat, 18 Apr 2015 23:31:34 +0200
From : laser@... (No=EBlBuhagiar)
Subject: bbc-micro Digest, Vol 102, Issue 7
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Message: 1
Date: Fri, 17 Apr 2015 23:44:00 +0200
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Message: 1
Date: Thu, 16 Apr 2015 22:10:31 +0200
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1. Re: bbc-micro Digest, Vol 102, Issue 3 (No?lBuhagiar)
2. Re: EPROM versus ROM for BBC/B OS1.2 (Peter Coghlan)
3. Re: EPROM versus ROM for BBC/B OS1.2 (Mark Haysman)
Message: 1
Date: Tue, 14 Apr 2015 23:41:04 +0200
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Today's Topics:
1. EPROM versus ROM for BBC/B OS1.2 (No?lBuhagiar)
2. Re: EPROM versus ROM for BBC/B OS1.2 (Daniel Jameson)
3. Re: EPROM versus ROM for BBC/B OS1.2 (Peter Coghlan)
4. Re: EPROM versus ROM for BBC/B OS1.2 (Storer, Darren)
5. Re: EPROM versus ROM for BBC/B OS1.2 (Jason Flynn G7OCD)
6. Re: EPROM versus ROM for BBC/B OS1.2 (Jason Flynn G7OCD)
Message: 1
Date: Mon, 13 Apr 2015 22:28:32 +0200
From: No?lBuhagiar <laser@...>
Subject: [BBC-Micro] EPROM versus ROM for BBC/B OS1.2
To: <bbc-micro@...>
Message-ID: <4FECD47526FF417180DE4CACDEF555A4@...>
>Hi,
>I have a question maybe some of you experts here would be so kind to answer
>please, thanks.
>Can I use an EPROM instead of ROM in my BBC-B? I tried to program an EPROM
>with OS1.2 but it didn?t work.
>Why didn?t it work??
>Thanks for your help,
>Noel
http://lists.cloud9.co.uk/pipermail/bbc-micro/attachments/20150413/ac934672/attachment-0001.html
Message: 2
Date: Mon, 13 Apr 2015 21:52:11 +0100
From: Daniel Jameson <djameson@...>
Subject: Re: [BBC-Micro] EPROM versus ROM for BBC/B OS1.2
To: bbc-micro@...
Message-ID:
<CAJ_qnrxmKUijrXTb+X8FXa3tGuyO2MP+F6VgdYDXBKOYmBnuxA@...>
>Really no reason why it shouldn't work, so long as the image was correct
>and the EPROM verified ok. Problem with the beeb?
>d.
Thanks for your reply.
It didn't work and I tried about 3 images taken from different sources.
EPROM verified ok and nothing wrong with the beeb as it works fine.
n.
http://lists.cloud9.co.uk/pipermail/bbc-micro/attachments/20150413/8b91b0e1/attachment-0001.html
Message: 3
Date: Mon, 13 Apr 2015 21:51:00 +0100 (WET-DST)
From: Peter Coghlan <bbcmicro@...>
Subject: Re: [BBC-Micro] EPROM versus ROM for BBC/B OS1.2
To: bbc-micro@...
Message-ID: <01PKRYHFKQGY0077MJ@...>
>
> Can I use an EPROM instead of ROM in my BBC-B?
>
>That should work.
>
> I tried to program an EPROM with OS1.2 but it didn't work.
> Why didn't it work??
>
>Wrong type of EPROM?
(ST)M27128A (should be 16K)
>Faulty EPROM?
No it worked before with a PRINTMASTER image.
>EPROM not properly erased before programming?
Verified blank ok.
>EPROM not correctly programmed?
Program verified ok with programmer.
>EPROM not correctly inserted in correct location?
Fitted in same location were original ROM was...1st from left side.
>Jumpers set for four 4K OS EPROMs instead of one 16K EPROM?
Shouldn' be as with ROM beeb worked.
>Some incompatibility between the hardware and OS1.2?
Fitted with Data-Center, so board was modified so that 2 ROM sockets are
seen as 3 each and another for 1 RAM
if I remember correctly.
>A 27128 EPROM should be suitable. I vaguely recall reading that a 250ns
>part
i>s supposed to be required but don't quote me on that. I think I've even
had
>success with 350ns parts in the paged ROM locations at least. It should be
>possible to get various other types of EPROM to work by suitable trickery.
>If you post more details, it may be possible to provide more detailed help.
Sorry, my fault, did not send enough information as I didn't expect I would
get so much interest & help!... thanks.
>Eg, why you want to replace your OS, whether the machine worked before you
>made changes to it, whether it works again now if you reverse the changes
>and
>what exactly you mean by "didn't work" - does the machine just beep
>continuously
>and show a blank screen when you power it up or does it just show the wrong
>colours in MODE 2 or something else in between those two extremes?
>What do you get on the screen, what state are the keyboard LEDs in and can
>you
>get them to change state using the caps lock and shift lock keys?
>Regards,
>Peter Coghlan.
Just experimenting, tried putting my name instead of eg: "BBC Computer".
The machine works fine with original ROM and also tried exact OS1.2 image in
EPROM to make sure but no go.
Machine beeps continuously and shows a blank screen when powered up.
Blank.. no screen.
Did not notice state of keyboard LEDs.... will do that soon.
noel
Message: 4
Date: Mon, 13 Apr 2015 22:46:34 +0100
From: "Storer, Darren" <darren.storer@...>
Subject: Re: [BBC-Micro] EPROM versus ROM for BBC/B OS1.2
To: No?lBuhagiar <laser@...>
Cc: BBC micro mailing list <bbc-micro@...>
Message-ID:
<CAHBhi2H29y57KcCPAPKr2ovDLTC=bShqcrM8=S7S5Cp3DKV=ig@...>
>Hi Noel,
>what size of EPROM did you program? What is the part number? E.g. 27C256.
>Depending on the capacity of the EPROM (E.g. 16 k) you can sometimes cheat
>by programming an 8 k image in the top half of the EPROM too (all to do
>with address lines).
>Best regards
>Darren
Should be 16K if not mistaken... an (ST)M27128A.
Thanks for the info...
noel
On 13 April 2015@..., No?lBuhagiar <laser@...> wrote:
> Hi,
>
> I have a question maybe some of you experts here would be so kind to
> answer please, thanks.
> Can I use an EPROM instead of ROM in my BBC-B? I tried to program an EPROM
> with OS1.2 but it didn?t work.
> Why didn?t it work??
>
> Thanks for your help,
> Noel
>
> _______________________________________________
> bbc-micro mailing list
> bbc-micro@...
> http://lists.cloud9.co.uk/mailman/listinfo/bbc-micro
>
>
http://lists.cloud9.co.uk/pipermail/bbc-micro/attachments/20150413/4ba33479/attachment-0001.html
Message: 5
Date: Mon, 13 Apr 2015 23:29:04 +0100
From: Jason Flynn G7OCD <flynnjs@...>
Subject: Re: [BBC-Micro] EPROM versus ROM for BBC/B OS1.2
To: bbc-micro@...
Message-ID: <552C4330.4090205@...>
>Does this help? :
>"When replacing this with a Series 1 Operating System ROM it should
>be noted that the carrier board has rather large diameter pins, which
>sometimes damage the IC socket into which the board was fitted."
>Take from:
>http://bbc.nvg.org/doc/A%20Hardware%20Guide%20for%20the%20BBC%20Microcomputer/bbc_hw_03.htm
This is not the case... large diameter pins, no... it?s a normal EPROM with
normal pins.
On 13/04/2015 22:46, Storer, Darren wrote:
> Hi Noel,
>
> what size of EPROM did you program? What is the part number? E.g. 27C256.
>
> Depending on the capacity of the EPROM (E.g. 16 k) you can sometimes
> cheat by programming an 8 k image in the top half of the EPROM too
> (all to do with address lines).
>
> Best regards
>
> Darren
>
> On 13 April 2015@..., No?lBuhagiar <laser@...
> <mailto:laser@...>> wrote:
>
> Hi,
> I have a question maybe some of you experts here would be so kind
> to answer please, thanks.
> Can I use an EPROM instead of ROM in my BBC-B? I tried to program
> an EPROM with OS1.2 but it didn?t work.
> Why didn?t it work??
> Thanks for your help,
> Noel
>
> _______________________________________________
> bbc-micro mailing list
> bbc-micro@... <mailto:bbc-micro@...>
> http://lists.cloud9.co.uk/mailman/listinfo/bbc-micro
>
>
>
>
> _______________________________________________
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> bbc-micro@...
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Message: 6
Date: Mon, 13 Apr 2015 23:32:15 +0100
From: Jason Flynn G7OCD <flynnjs@...>
Subject: Re: [BBC-Micro] EPROM versus ROM for BBC/B OS1.2
To: bbc-micro@...
Message-ID: <552C43EF.8080309@...>
>I also have a recollection of the OS ROM running at 2MHz but the SW ROMS
>only being 1MHz.
>Is your EPROM fast enough to meet 2MHz ? (although I could be
>remembering wrongly and
>don't have time to check the schematic).
Don't know about this... will try to verify if I can, thanks.
noel
On 13/04/2015 21:52, Daniel Jameson wrote:
>
> Really no reason why it shouldn't work, so long as the image was
> correct and the EPROM verified ok. Problem with the beeb?
>
> d.
>
>
>
> _______________________________________________
> bbc-micro mailing list
> bbc-micro@...
> http://lists.cloud9.co.uk/mailman/listinfo/bbc-micro
_______________________________________________
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End of bbc-micro Digest, Vol 102, Issue 3
*****************************************
Message: 2
Date: Wed, 15 Apr 2015 00:48:59 +0100 (WET-DST)
From: Peter Coghlan <bbcmicro@...>
Subject: Re: [BBC-Micro] EPROM versus ROM for BBC/B OS1.2
To: bbc-micro@...
Message-ID: <01PKTHXCJGLM005BGE@...>
>
>> Wrong type of EPROM?
> (ST)M27128A (should be 16K)
>
I found a data sheet for the M27128A-2F1 by ST Microelectronics on the web
and I had a look through it. As far as I can see, it should be suitable.
The
M27128A-2F1 variant is 200ns which is more than fast enough. Hopefully it
is
not too fast! (The M27128A-F1 is 250ns - that should work too and the
M27128-3F1 is 300ns which might also work.)
>
>> EPROM not correctly programmed?
> Program verified ok with programmer.
>
Can you read the original OS ROM in your EPROM programmer (without trying to
program it and without applying the programming voltage) and compare the
image
with the image you are programming into the EPROM? This might show up any
problems in transferring the image from wherever it is coming from, to the
EPROM programmer.
>> Some incompatibility between the hardware and OS1.2?
> Fitted with Data-Center, so board was modified so that 2 ROM sockets are
> seen as 3 each and another for 1 RAM
> if I remember correctly.
>
I'm not familiar with that item - I don't know if it would have any bearing
on the problem. I guess if it works with OS1.2 in a ROM, it should work
equally well with OS1.2 in an EPROM. If it has connections to jumpers on
the
beeb circuit board, it may be suspect.
>
> Sorry, my fault, did not send enough information as I didn't expect I
> would
> get so much interest & help!... thanks.
>
Don't worry - there are teams of BBC micro people lying in wait for
interesting
problems to solve :-)
>
> Just experimenting, tried putting my name instead of eg: "BBC Computer".
> The machine works fine with original ROM and also tried exact OS1.2 image
> in
> EPROM to make sure but no go.
> Machine beeps continuously and shows a blank screen when powered up.
> Blank.. no screen.
>
Looks like the EPROM is not being accessed correctly or the CPU is not
managing
to read the startup code from it. I suspect the behaviour would be the same
with no OS plugged in.
I don't have a data sheet for the ROM but from looking at the model B
circuit
diagram, it seems very likely that the only differences between the ROM and
an
EPROM could be at pins 1 and 27. The EPROM data sheet says that these
should
both be high when reading from the device but is not very explicit on what
will
happen if they are not high. The circuit diagram says they are connected to
A14 and A15 (which are both high any time OS locations are being accessed).
Perhaps these two pins are not connected to anything on the ROM? If so and
there was a fault with connections to either of those two pins on the
circuit
board, a problem might show up when an EPROM is used but not a ROM. It
might
be worth verifying that these two pins are correctly connected to A14 and
A15.
>
>> Does this help? :
>> "When replacing this with a Series 1 Operating System ROM it should
>> be noted that the carrier board has rather large diameter pins, which
>> sometimes damage the IC socket into which the board was fitted."
>
>> Take from:
>> http://bbc.nvg.org/doc/A%20Hardware%20Guide%20for%20the%20BBC%20Microcomputer/bbc_hw_03.htm
>
>
> This is not the case... large diameter pins, no... it's a normal EPROM
> with
> normal pins.
>
I wouldn't rule out problems with the socket. They are not very good
sockets
and they can end up making good contact with pins on one chip which are bent
one way and poor contact with pins on another chip which are bent slightly
differently.
Regards,
Peter Coghlan.
Message: 3
Date: Wed, 15 Apr 2015 09:52:34 +0100
From: "Mark Haysman" <jumbos.bazzar@...>
Subject: Re: [BBC-Micro] EPROM versus ROM for BBC/B OS1.2
To: <bbc-micro@...>
Message-ID: <B2AD312038C746F68A182AE9A12FC621@...>
>> Some incompatibility between the hardware and OS1.2?
> Fitted with Data-Center, so board was modified so that 2 ROM sockets are
> seen as 3 each and another for 1 RAM
> if I remember correctly.
>
Hi. I make the DataCentre, and do the mods to the Beeb you have.
There are three modified sockets, the far right one is for a 32K RAM chip,
so pin 27 is connected to a /WR line across the board. The next two are
modified to take 27512s, so can have 4 ROM images in each position. The
modified sockets are backwards compatible to 27256 and 27128.
You shouldn't have any compatibility issues using faster ROMs in the Beeb,
I've used Atmel 45ns access chips with no reliability issues at all.
Mark.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
- - - - - - - - - -
Thank you all for your suggestions and info especially Peter Coghlan who in
my
opinion was very observant and accurate in his analysis. Thanks also to Mark
for
reminding me about 4 ROM images and not 3 as I stated in each position and
then
using combi-ROM. Also a 32K RAM chip at the rightmost socket... as SWR.
Well, I now got it working... like Peter stated, only difference from
leftmost socket (were
the OS sits) from all the others was pin 1 & 27. I found from datasheet of
the original OS
MaskRom HN613128 that pin 1 was not connected (NC). Pin 1 of the EPROM I
used, an
M27128A-2F1 was Vpp (Program supply). I bent slightly this pin sideways
before inserting
the chip into 1st (OS) socket so that no contact was made and found that now
the beeb
powered-up and worked as usual.... hurray!
What I do not understand is why it effected the chip as when I traced (OS)
socket pin 1 on schematic
I found this only went to a quad OR gate input namely IC29 (74LS32) pin 4.
Now why did it effect the
EPROM chip with only pin 4 of IC29 being an input? Also, why did they
connect this pin knowing that
the OS MaskROM chip did not use pin 1 it being NC??
Anyway guys, thank you all for your replies and support I appreciate it a
lot and apologize for
my pehaps..... not so good explanation .
noel
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End of bbc-micro Digest, Vol 102, Issue 4
*****************************************
Message: 2
Date: Fri, 17 Apr 2015 00:01:44 +0100 (WET-DST)
From: Peter Coghlan <bbcmicro@...>
Subject: Re: [BBC-Micro] EPROM versus ROM for BBC/B OS1.2
To: bbc-micro@...
Message-ID: <01PKW6OQ28LI0078UF@...>
>
> Thank you all for your suggestions and info especially Peter Coghlan who
> in my
> opinion was very observant and accurate in his analysis. Thanks also to
> Mark
> for reminding me about 4 ROM images and not 3 as I stated in each position
> and then using combi-ROM. Also a 32K RAM chip at the rightmost socket...
> as
> SWR.
>
> Well, I now got it working... like Peter stated, only difference from
> leftmost socket (were the OS sits) from all the others was pin 1 & 27. I
> found
> from datasheet of the original OS MaskRom HN613128 that pin 1 was not
> connected (NC). Pin 1 of the EPROM I used, an M27128A-2F1 was Vpp (Program
> supply). I bent slightly this pin sideways before inserting the chip into
> 1st (OS) socket so that no contact was made and found that now the beeb
> powered-up and worked as usual.... hurray!
>
Great stuff - good to hear you have it working now. I would suggest you
link
the bent out pin 1 over to pin 28 as the data sheet says it should be
connected
to Vcc and it might not be good to leave it floating.
#N: Good idea, good point... however now I've checked with the other ROM
sockets
and it seems their pin 1 is not connected to anything (like you said below)
except
I discovered they are connected to each other.
>
> What I do not understand is why it effected the chip as when I traced (OS)
> socket pin 1 on schematic I found this only went to a quad OR gate input
> namely IC29 (74LS32) pin 4. Now why did it effect the EPROM chip with only
> pin 4 of IC29 being an input?
>
My schematic shows pin 1 on the OS socket connected to A15 which goes to
IC29
pin 4 and also to a few other places including pin 25 on IC1, the 6502 CPU.
The CPU should be driving this line high whenever the OS is accessed
(because
the OS is in the top half of the memory).
Going back to the EPROM data sheet, it suggests that in read mode, the EPROM
will draw Ipp = 5mA through pin 1. This sounds a bit high. Maybe it is
dragging down the level on A15 when it is connected and this is the cause of
the problem? On the other hand, if pin 1 is disconnected and the EPROM is
unable to draw 5mA through it, I would have thought that the EPROM would
then
not function, unless this 5mA is not actually required for anything, in
which
case, why does the data sheet require that pin to be connected to Vcc?
Strange.
In the case of the paged ROMS, it appears from my schematic that pin 1 of
the
sockets is not connected to anything so if this is the correct diagnosis, it
looks likely that the problem would not arise for paged ROMs, only the OS.
#N: Could it be the designers did not want an EPROM plugged in the OS socket
for
some reason? For example: I looked at both MaskRom & EPROM data sheets
and the supply current of the MaskROM is much lower then that of the EPROM
both when active & on standby.
>
> Also, why did they connect this pin knowing that the OS MaskROM chip did
> not
> use pin 1 it being NC??
>
Having A15 on pin 1 and A14 on pin 27 would be compatible with a 27512 but
it's
hard to see how this would be useful as only a quarter of it could be
accessed
without further changes. Linking the NE pin of S21 to 0V would allow the
27512
to take over the entire 64K memory map (except for the I/O areas) but why
would
anyone want to do that as the machine would be very limited with no RAM
accessible? Even if (slower) paged RAM was provided on the 1MHz bus, there
would still be no access to the stack, page zero and the screen making the
machine almost useless. Some minor changes around IC21 might allow the OS
image plus a single paged ROM image to be held in the 27512 with only half
of
it wasted but this doesn't seem like a very useful thing to do either.
Maybe it was just felt to just be a good place to route all the address
lines
where they could be picked up by an adapter board plugged into the OS ROM
socket or something like that? On the other hand, other very useful signals
such as R/W- are not present there.
Maybe someone else knows what the original designers were thinking of here?
#N: Does anyone know who the original designers are or were?
I try to check this out later with a very interesting DVD sent to me from UK
featuring
the BBC-B versus the Sinclair Spectrum story.
>
> Anyway guys, thank you all for your replies and support I appreciate it a
> lot and apologize for my pehaps..... not so good explanation .
>
I'm glad that you've made progress with the problem. Your explanation was
fine.
#N: thanks
Regards,
Peter Coghlan
#N: regards, noel
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End of bbc-micro Digest, Vol 102, Issue 5
*****************************************
Message: 2
Date: Sat, 18 Apr 2015 10:43:49 +0100
From: "J.G.Harston" <jgh@...>
Subject: Re: [BBC-Micro] EPROM versus ROM for BBC/B OS1.2
To: bbc-micro@...
Message-ID: <148ad700c0ecf38b5729e2b0902ae7f1@...>
Peter Coghlan wrote:
> Maybe it was just felt to just be a good place to route all the address
> lines
> where they could be picked up by an adapter board plugged into the OS
> ROM
> socket or something like that? On the other hand, other very useful
> signals
> such as R/W- are not present there.
Those pins are there because on the very first test machines the OS was
in four 4K EPROMs plugged into the four sideways ROM slots with the 16K
BASIC plugged into the MOS socket. Changing the pin links around swapped
the functionality of the five sockets.
Later test machines has the OS in two EPROMS on a header board plugged
into the MOS socket.
jgh
So most replies here seem to have been on the right track.
Thank you Sir for this rare (at least to me) info, you have quenched my
curiosity at last.
noel
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Message: 2
Date: Sat, 18 Apr 2015 21:59:47 +0100 (WET-DST)
From: Peter Coghlan <bbcmicro@...>
Subject: Re: [BBC-Micro] EPROM versus ROM for BBC/B OS1.2
To: bbc-micro@...
Message-ID: <01PKYXQR0E520079Z5@...>
jgh wrote:
>
> Those pins are there because on the very first test machines the OS was
> in four 4K EPROMs plugged into the four sideways ROM slots with the 16K
> BASIC plugged into the MOS socket. Changing the pin links around swapped
> the functionality of the five sockets.
>
I can't see why A14 and A15 being present on the MOS socket was required
either
for the four 4K OS EPROMs or for BASIC to function in the MOS socket.
What use could A14 and A15 be to a 16K BASIC? I suppose they could be
decoded
by a ROM with several select lines to map BASIC into 4000-7FFF for example
but
was this ever done?
>
> Later test machines has the OS in two EPROMS on a header board plugged
> into the MOS socket.
>
I could see how some logic on the header board could decode A14 and A15 if
this was necessary but I can't see why it would be necessary because they
are decoded by IC21 and the enable signal for either 8000-BFFF or C000-FFFF
is selected by S21 and fed through to pin 20.
Regards,
Peter Coghlan.
I regret to say that here my curiosity came haunting me back.
But then again, my wish is to try to comprehend the truth.
Once again I do have to congratulate you with your good if not excellent
analysis.
noel
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