Enable CD-ROM via a synchronous fs-backed buffer#362
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v86's async loaders leave the ATAPI drive in BSY across an event-loop turn after a READ(10) CDB. Win95's ESDI_506 reads status twice, sees BSY both times, and issues DEVICE RESET ~165 instructions later, which cancels the in-flight read — the drive enumerates but D: never mounts. Serve the ISO through a small fs.readSync-backed buffer so the data is available before the next emulated instruction runs, and re-enable the CD-ROM settings tab. Also: WIN95_PROBE_CDROM / WIN95_PROBE_CDTRACE harness hooks, and pump one screen-adapter frame before screenshotting so probe captures work when the Electron window is occluded.
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What
Re-enables the CD-ROM settings tab and makes mounted ISOs actually readable from inside Windows 95.
Why it never worked
v86's stock async loaders (
AsyncXHRBuffer/AsyncFileBuffer) return from.get()immediately and resolve on the next event-loop turn. For an ATAPI PIO READ(10) that meansatapi_read()leaves the drive in BSY while ~1.3 M emulated instructions run before the data callback fires.Win95's ESDI_506/CDVSD path reads status twice right after pushing the CDB, sees
0xD0(BSY) both times, and issues DEVICE RESET (08h) ~165 instructions later — which cancels the in-flight read viacancel_io_operations(). It retries once, gets the same result, gives up. The drive enumerates and D: appears, but the volume never mounts (label shows as "CD",dir d:is empty).The hard disk doesn't hit this because ESDI_506 drives it via bus-master DMA, which is purely IRQ-driven on the host side.
Fix
SyncFileBuffer(src/renderer/sync-file-buffer.ts) implements v86's{get, set, load, byteLength, get_state, set_state}buffer contract on top offs.readSync, so each 2 KB sector is available before the next emulated instruction runs. Wired inemulator.tsxin place of{url, async: true}.Verified end-to-end with the probe harness: mount the XP SP3 ISO from ~/Downloads, boot to desktop,
dir d:listsGRTMPVOL_ENwith the full root directory; ATAPI trace shows 8 READ(10)s and only the boot-time detection RESET.Also in this PR
WIN95_PROBE_CDROM=/path.isoandWIN95_PROBE_CDTRACE=1harness hooks (and skill doc) for reproducing the above without the UI.screen_adapter.update_screen()frame before each probe screenshot — rAF doesn't fire when the Electron window is occluded, so captures were coming back blank.Reviewer note
Don't switch the cdrom option back to
{url, async: true}without re-testingdir d:inside the guest — it'll silently regress to an unmountable drive.