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  • GS ROM Upgrade Problem

    From Mike Spangler@mspangler@ifiber.tv to comp.sys.apple2 on Tuesday, March 30, 2021 16:36:17
    From Newsgroup: comp.sys.apple2

    I was intending to upgrade a ROM 0 GS to ROM 1. So I built the usual socket adapter for a 27C010 as per various sources, and it fails to work. OE and CE are jumpered together at the EPROM's level, pin 22 on the MB socket (A16) is routed to pin 2 on the EPROM, and the power is jumpered appropriately. But nothing happens when it's plugged in.
    And by nothing I mean the GS acts exactly like it does if you start it with no ROM at all. Very blank screen, no crash into the monitor or any other sign of CPU life.
    I checked continuity up through the sockets to the EPROM, and it is all as it should be, (pin 22 on the MB side is not connected to pin 24 on the EPROM, otherwise they all go through. A logic probe shows power and ground are fine, and the various address and data lines are all pulsing at the EPROM level. So some sort of signal is getting through.
    I built a second socket rig with CE on the EPROM tied directly to ground and got the same result. The data sheets said that CE should be pulled low first. It didn't help. I also pulled PGM high just to make sure it was not doing anything, that also had no effect. VPP is unconnected, which is not supposed to matter. and Pin 30 of the EPROM does have power applied to it, but it's not supposed to be connected internally, so that shouldn't matter.
    The 27C010 is a Fairchild, 120 NS, which should be fast enough.
    I did tweak the ROM in by editing Applesoft between D000 and F800 (replacing the cassette/DLRG commands with something more useful), nothing changed above or below that. I could have run into some checksum problem, but again, it's not executing any code as far as I can tell. And the modified applesoft runs fine on a 2E.
    Any suggestions?
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  • From cruff@cruff@ruffspot.net (Craig Ruff) to comp.sys.apple2 on Tuesday, March 30, 2021 20:18:11
    From Newsgroup: comp.sys.apple2

    In article <9df419e4-961d-4146-a4fe-4c1febcb6bc1n@googlegroups.com>,
    Mike Spangler <mspangler@ifiber.tv> wrote:
    I built a second socket rig with CE on the EPROM tied directly to ground and got the same result. The data
    sheets said that CE should be pulled low first. It didn't help. I also pulled PGM high just to make sure it was
    not doing anything, that also had no effect. VPP is unconnected, which is not supposed to matter. and Pin 30 of
    the EPROM does have power applied to it, but it's not supposed to be connected internally, so that shouldn't
    matter.

    An Atmel 27C010 datasheet says /PGM should be pulled to either Vih or Vil
    for reads with /CE and /OE both pulled low, so you should be good there.
    Vpp should be either Vih or Vil, not floating. Have you tried pulling
    Vpp to GND?
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  • From Nick Westgate@nick.westgate@gmail.com to comp.sys.apple2 on Wednesday, March 31, 2021 00:28:06
    From Newsgroup: comp.sys.apple2

    On Wednesday, March 31, 2021 at 9:36:19 AM UTC+10, mspa...@ifiber.tv wrote:
    I did tweak the ROM in by editing Applesoft between D000 and F800 (replacing the cassette/DLRG commands with something more useful), nothing changed above or below that. I could have run into some checksum problem, but again, it's not executing any code as far as I can tell. And the modified applesoft runs fine on a 2E.

    Any suggestions?
    I think you will run into checksum problems. Here are two relevant threads. The more recent ROM 1 thread refers to the earlier ROM 3 thread.
    https://comp.emulators.apple2.narkive.com/1xSckady/gs-rom-1-checksum https://comp.sys.apple2.narkive.com/zc8aaQVL/creating-a-new-apple-iigs-rom-03-checksum
    Cheers,
    Nick.
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  • From Mike Spangler@mspangler@ifiber.tv to comp.sys.apple2 on Wednesday, March 31, 2021 14:53:44
    From Newsgroup: comp.sys.apple2

    I can certainly try grounding VPP. It can't hurt. But there will be a slight delay, as both my RIFA capacitors blew up in the ROM 3 power supply. At least it wasn't the monitor. Oddly enough, the GS stayed running very happily throughout the pop and ensuing smoke cloud. Obviously they are not very important.
    The other capacitors seem to be fine. No bulging or discolored traces near them.
    If there anything special about these RIFA capacitors other than they like to blow up? Or will any .22 microF 250 V capacitor do?
    As for the checksum calculation, is that in ROM or GSOS? If it's in ROM it can disappear very easily once found since I am rewriting it anyway. ProDOS's checksum has no problem with my Applesoft mods. But that only checks the APPLE// message in the F8 ROM area. I'm sure the self test would throw a huge fuss, but there is no self test in the debug rom.
    One other note, This particular ROM 3 GS has a 32 pin socket and a standard 128 X8 EPROM in the FE-FF ROM position. The FC-FD ROM is a 28 pin mutant thing. Odd.
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  • From Michael J. Mahon@mjmahon@aol.com to comp.sys.apple2 on Wednesday, March 31, 2021 17:36:28
    From Newsgroup: comp.sys.apple2

    Mike Spangler <mspangler@ifiber.tv> wrote:
    I can certainly try grounding VPP. It can't hurt. But there will be a
    slight delay, as both my RIFA capacitors blew up in the ROM 3 power
    supply. At least it wasn't the monitor. Oddly enough, the GS stayed
    running very happily throughout the pop and ensuing smoke cloud.
    Obviously they are not very important.

    The other capacitors seem to be fine. No bulging or discolored traces near them.
    If there anything special about these RIFA capacitors other than they
    like to blow up? Or will any .22 microF 250 V capacitor do?

    Not just any capacitor, but an “X2” capacitor, which is a polypropylene dielectric capacitor designed to “burn open” small shorts, making it suitable for connecting directly across the AC power line. The dreaded
    failure occurs when too many or too large shorts occur, usually the result
    of a transient spike on the AC line.

    The good news is that they are inexpensive and readily available.

    --
    -michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
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  • From Mike Spangler@mspangler@ifiber.tv to comp.sys.apple2 on Wednesday, March 31, 2021 19:19:38
    From Newsgroup: comp.sys.apple2

    I found out the same thing and have them on order. I got enough to replace them in the other GS power supplies too. And the .1 uF for the IIe units too.
    On Wednesday, March 31, 2021 at 3:36:35 PM UTC-7, Michael J. Mahon wrote:
    Mike Spangler <mspa...@ifiber.tv> wrote:
    I can certainly try grounding VPP. It can't hurt. But there will be a slight delay, as both my RIFA capacitors blew up in the ROM 3 power supply. At least it wasn't the monitor. Oddly enough, the GS stayed running very happily throughout the pop and ensuing smoke cloud.
    Obviously they are not very important.

    The other capacitors seem to be fine. No bulging or discolored traces near them.
    If there anything special about these RIFA capacitors other than they
    like to blow up? Or will any .22 microF 250 V capacitor do?
    Not just any capacitor, but an “X2” capacitor, which is a polypropylene dielectric capacitor designed to “burn open” small shorts, making it suitable for connecting directly across the AC power line. The dreaded failure occurs when too many or too large shorts occur, usually the result of a transient spike on the AC line.

    The good news is that they are inexpensive and readily available.

    --
    -michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
    --- Synchronet 3.18b-Win32 NewsLink 1.113
  • From geoff body@gbody4@bigpond.com to comp.sys.apple2 on Tuesday, April 06, 2021 05:08:26
    From Newsgroup: comp.sys.apple2

    Is the file available that you are using to program the EPROM
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