EPROMs too slow?

A500Man · 17 October 2011, 19:17

Hi there,

I own an Amiga 500 with a Kickstart 3.1 original chip. To preserve the original Chip I ordered "AMD 27C400-150" EPROMs and had the data contend of the original Kickstart-chip programmed onto a 27C400-EPROM.

Now, placing the EPROM onto my Kickstart-Switch makes no problem, it is working fine. But placing the EPROM directly into the ROM-Socket on the motherboard (Rev. 6a) results in permanent reboots / black screen. I doublechecked and veryfied; the EPROM`s content matches the Original 100%.

Well, what is that? Is the EPROM too slow? I guess not, since I heard of working EPROMs with a speed of -200. But why does it work in that Kickstart-switch (2 Kick-Sockets, one 74LS00-chip) but not stand-alone?

What could it be? Can I "heal" the problem or can I bin the EPROM? Anyone with an idea?

CU,
A500Man

yaqube · 17 October 2011, 21:37

Was your kick-switcher populated also with the original kickstart chip? If so does the 27c400 work in the switcher alone (the other chip removed)?

A500Man · 17 October 2011, 22:02

Yep,

I tried the Kickstart-switch with (only) the original Chip; it worked.

Does anyone know what the speed of the original Amiga Kickstart 1.3 is?

Hm, the original Kickstart 3.1 is on a "MX23C4100". It does not state a timing, but the MX23C4100 is avaiable in -100, -120 and -150. I fear the Amiga-ROMs are the -100 or -120 types ... Can anyone verify?

CU,
A500Man

yaqube · 17 October 2011, 23:07

Quote:

Originally Posted by A500Man

I tried the Kickstart-switch with (only) the original Chip; it worked.

Does your 27C400 work in the kick-switcher with empty second socket?
The problem might be caused by lacking pull-up resistors on the motherboard.

mfilos · 17 October 2011, 23:26

150 is too slow for Amiga use sadly.

Get 100ns ones or at worst 120ns.

A500Man · 17 October 2011, 23:40

@yaqube: Sorry, ma english is not too good, I got you wrong. Now I understand: No, when I place only the original Chip and NO other ROM-Chip on the Kickstart-switch the Amiga does not boot. The same for the 27C400.

What do you mean with pullup-resistor? Could I solder an resistor to the 27C400 to help solving the problem?

@mfilos: I tried it with an "AMD 27C400-105" a few minutes ago; the same Problem: permanent re-boot.

CU,
A500Man

A500Man · 17 October 2011, 23:48

@yaqube: Sorry, ma english is not too good, I got you wrong. Now I understand: No, when I place only the original Chip and NO other ROM-Chip on the Kickstart-switch the Amiga does not boot. The same for the 27C400.

What do you mean with pullup-resistor? Could I solder an resistor to the 27C400 to help solving the problem?

@mfilos: I tried it with an "AMD 27C400-105" a few minutes ago; the same Problem: permanent re-boot. But as I reported: Placing the EPROM on the Kickstart-Switch makes it run.

CU,
A500Man

musashi5150 · 18 October 2011, 08:21

Seems too strange to be a speed problem... The A4000 mobo has jumper to select 160/200ns speeds - which is far slower than the 105 you are testing with and the A4000 is much faster

Maybe the ROM socket on your mobo has a loose pin-hole? As it works in your ROM swapper -are the legs of your ROM swapper larger?

voxel · 18 October 2011, 10:47

hi :-)

what is the version/revision of your A500 motherboard ?
what is the screen color displayed when the eprom is on the motherboard ?

yaqube · 18 October 2011, 16:21

Quote:

Originally Posted by A500Man

@yaqube: Sorry, ma english is not too good, I got you wrong. Now I understand: No, when I place only the original Chip and NO other ROM-Chip on the Kickstart-switch the Amiga does not boot. The same for the 27C400.

What do you mean with pullup-resistor? Could I solder an resistor to the 27C400 to help solving the problem?

I had the same issue: http://eab.abime.net/showthread.php?p=525862#post525862

If your motherboard revision is 6 or 8 just populate RP106 and RP107.

A500Man · 18 October 2011, 22:41

Jepp,

thank`s yaqube! You gave me an idea and I did some research: the 27C400 has a usual power consumation of 15 mA. The Original Kickstart chips consumes 50 or 60 mA.

Hmpf.

CU,
A500Man

rampartsagain · 13 June 2014, 19:48

Does any one knows if amga can work with faster kickroms like 50 or 70 nanoseconds ?

regards

hooverphonique · 16 June 2014, 14:35

Quote:

Originally Posted by rampartsagain

Does any one knows if amga can work with faster kickroms like 50 or 70 nanoseconds ?

As long as they are as fast or faster than the originals, it should work..

FOL · 17 June 2014, 20:36

Quote:

Originally Posted by mfilos

150 is too slow for Amiga use sadly.

Get 100ns ones or at worst 120ns.

Not true, Ive used 140 and it works perfectly fine.

tom256 · 18 June 2014, 05:19

Quote:

Originally Posted by rampartsagain

Does any one knows if amga can work with faster kickroms like 50 or 70 nanoseconds ?

regards

No, access time is set pernamently.

suppah · 24 April 2022, 12:06

Quote:

Originally Posted by FOL

Not true, Ive used 140 and it works perfectly fine.

Did you guys ever benchmark rom access speed ? Bustest has also rom access speed (at least bandwidth speed and not latency speed though) but if A4000 is set to 160/200 im guessing indeed everything talked about here is even faster than normal roms.

according to this standard roms (or at least some version of them) are 150ns.

https://www.amiga-stuff.com/hardware/2mbit-maskrom.html

dmacon · 24 April 2022, 12:25

Quote:

Originally Posted by mfilos

150 is too slow for Amiga use sadly.

Get 100ns ones or at worst 120ns.

A 68000 bus cycle is 560ns in an Amiga 500. Even if you account for the negligible set-up times for /AS, 150ns ROMs are actually way too fast already…

r.cade · 24 April 2022, 17:37

As mentioned, if Rev.6 or Rev.8, you need to make sure the resistor packs are installed. If it's Rev5 (or Rev.3 probably) then you need a kickstart adapter with the resistors integrated.

With that said, I've had random luck with the EPROMs from far east. I don't know if they are repainted much slower ROMs or just defective, but I've had several not work, even though you can program and verify them.

17 October 2011, 19:17	#1
A500Man Registered User Join Date: Oct 2010 Location: Germany Posts: 20	EPROMs too slow? Hi there, I own an Amiga 500 with a Kickstart 3.1 original chip. To preserve the original Chip I ordered "AMD 27C400-150" EPROMs and had the data contend of the original Kickstart-chip programmed onto a 27C400-EPROM. Now, placing the EPROM onto my Kickstart-Switch makes no problem, it is working fine. But placing the EPROM directly into the ROM-Socket on the motherboard (Rev. 6a) results in permanent reboots / black screen. I doublechecked and veryfied; the EPROM`s content matches the Original 100%. Well, what is that? Is the EPROM too slow? I guess not, since I heard of working EPROMs with a speed of -200. But why does it work in that Kickstart-switch (2 Kick-Sockets, one 74LS00-chip) but not stand-alone? What could it be? Can I "heal" the problem or can I bin the EPROM? Anyone with an idea? CU, A500Man

17 October 2011, 22:02	#3
A500Man Registered User Join Date: Oct 2010 Location: Germany Posts: 20	Yep, I tried the Kickstart-switch with (only) the original Chip; it worked. Does anyone know what the speed of the original Amiga Kickstart 1.3 is? Hm, the original Kickstart 3.1 is on a "MX23C4100". It does not state a timing, but the MX23C4100 is avaiable in -100, -120 and -150. I fear the Amiga-ROMs are the -100 or -120 types ... Can anyone verify? CU, A500Man Last edited by A500Man; 17 October 2011 at 22:37.

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17 October 2011, 21:37	#2
yaqube Registered User Join Date: Mar 2008 Location: Poland Posts: 159	Was your kick-switcher populated also with the original kickstart chip? If so does the 27c400 work in the switcher alone (the other chip removed)?

17 October 2011, 23:26	#5
mfilos Paranoid Amigoid Join Date: Mar 2008 Location: Athens/Greece Age: 45 Posts: 1,978	150 is too slow for Amiga use sadly. Get 100ns ones or at worst 120ns.

17 October 2011, 23:40	#6
A500Man Registered User Join Date: Oct 2010 Location: Germany Posts: 20	@yaqube: Sorry, ma english is not too good, I got you wrong. Now I understand: No, when I place only the original Chip and NO other ROM-Chip on the Kickstart-switch the Amiga does not boot. The same for the 27C400. What do you mean with pullup-resistor? Could I solder an resistor to the 27C400 to help solving the problem? @mfilos: I tried it with an "AMD 27C400-105" a few minutes ago; the same Problem: permanent re-boot. CU, A500Man

17 October 2011, 23:48	#7
A500Man Registered User Join Date: Oct 2010 Location: Germany Posts: 20	@yaqube: Sorry, ma english is not too good, I got you wrong. Now I understand: No, when I place only the original Chip and NO other ROM-Chip on the Kickstart-switch the Amiga does not boot. The same for the 27C400. What do you mean with pullup-resistor? Could I solder an resistor to the 27C400 to help solving the problem? @mfilos: I tried it with an "AMD 27C400-105" a few minutes ago; the same Problem: permanent re-boot. But as I reported: Placing the EPROM on the Kickstart-Switch makes it run. CU, A500Man

18 October 2011, 08:21	#8
musashi5150 move.w #$4489,$dff07e Join Date: Sep 2005 Location: Norfolk, UK Age: 42 Posts: 2,351	Seems too strange to be a speed problem... The A4000 mobo has jumper to select 160/200ns speeds - which is far slower than the 105 you are testing with and the A4000 is much faster Maybe the ROM socket on your mobo has a loose pin-hole? As it works in your ROM swapper -are the legs of your ROM swapper larger?

18 October 2011, 10:47	#9
voxel Amiga Nuts! Join Date: Sep 2006 Location: Le Mayet d'Ecole, 03800, FRANCE Posts: 176	hi :-) what is the version/revision of your A500 motherboard ? what is the screen color displayed when the eprom is on the motherboard ?

18 October 2011, 22:41	#11
A500Man Registered User Join Date: Oct 2010 Location: Germany Posts: 20	Jepp, thank`s yaqube! You gave me an idea and I did some research: the 27C400 has a usual power consumation of 15 mA. The Original Kickstart chips consumes 50 or 60 mA. Hmpf. CU, A500Man

13 June 2014, 19:48	#12
rampartsagain Registered User Join Date: May 2012 Location: Porto/Portugal Posts: 385	Does any one knows if amga can work with faster kickroms like 50 or 70 nanoseconds ? regards

24 April 2022, 17:37	#18
r.cade Registered User Join Date: Aug 2006 Location: Augusta, Georgia, USA Posts: 550	As mentioned, if Rev.6 or Rev.8, you need to make sure the resistor packs are installed. If it's Rev5 (or Rev.3 probably) then you need a kickstart adapter with the resistors integrated. With that said, I've had random luck with the EPROMs from far east. I don't know if they are repainted much slower ROMs or just defective, but I've had several not work, even though you can program and verify them.

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